WO2004006394A1 - Optical wave guide and method for manufacture thereof - Google Patents

Optical wave guide and method for manufacture thereof Download PDF

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Publication number
WO2004006394A1
WO2004006394A1 PCT/JP2003/008241 JP0308241W WO2004006394A1 WO 2004006394 A1 WO2004006394 A1 WO 2004006394A1 JP 0308241 W JP0308241 W JP 0308241W WO 2004006394 A1 WO2004006394 A1 WO 2004006394A1
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WO
WIPO (PCT)
Prior art keywords
core
rare earth
optical waveguide
concentration
earth element
Prior art date
Application number
PCT/JP2003/008241
Other languages
French (fr)
Japanese (ja)
Inventor
Akio Furukawa
Tuyoshi Shimoda
Yukari Deki
Original Assignee
Nec Corporation
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Publication date
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Publication of WO2004006394A1 publication Critical patent/WO2004006394A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1228—Tapered waveguides, e.g. integrated spot-size transformers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12035—Materials
    • G02B2006/1208—Rare earths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12083—Constructional arrangements
    • G02B2006/121—Channel; buried or the like
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength

Definitions

  • the present invention relates to an optical waveguide using a planar waveguide and a method for manufacturing the same, and more particularly to an optical waveguide having an optical amplification effect by adding a rare earth element to a glass waveguide.
  • Optical amplifiers are a very important device in recent long-distance WDM communications because they directly amplify light without passing through electric circuits and amplify over a wide wavelength range.
  • optical amplifiers using fibers doped with rare earth elements such as erbium are mainly used, and high quality amplifiers with high amplification gain and low noise characteristics are provided.
  • optical amplifiers with rare-earth elements added to planar optical waveguides have been developed with the aim of further miniaturization, and optical amplifiers aiming for higher gain and wider amplification band have been developed. Is being done.
  • concentration of the rare earth element to be added may be increased.
  • pumping light is introduced from the outside into an optical amplifier to excite rare-earth electrons, which are relaxed by signal light, and the intensity of the original signal light is increased by stimulated emission. Therefore, in order to increase the gain efficiently, more pump levels should be provided in the waveguide. Therefore, by introducing more rare earth elements such as erbium as a source for generating an excitation level into the waveguide, both miniaturization and high gain can be achieved.
  • rare earths have the property of clustering when added at high concentrations into the waveguide glass.
  • the excitation level changes and the number of rare earth elements contributing to excitation at the desired wavelength is substantially reduced, reducing the amplification gain. Therefore, in order to achieve both miniaturization and high gain, it is only necessary to increase the rare-earth concentration in the waveguide glass while suppressing clusters.
  • Important characteristics required for optical amplifiers include high gain and a wide amplification wavelength band. In wavelength multiplex communication, for example, optical signals of 40 kinds of wavelengths are used at 0.8 nm intervals, and a total of 32 nm wavelength band is used. An optical amplifier used in such wavelength division multiplexing communication is required to have a function of amplifying a gain in a band of 32 nm or more.
  • the assisting element only needs to be in the rare earth-containing layer, and in the above technique, it is not added to a region other than the center of the core because it contributes to light absorption.
  • the above-mentioned optical amplifier is also required to be smaller.
  • the gain per unit length in the waveguide direction is increased to shorten and reduce the size of the optical amplifier.
  • An optical waveguide according to the present invention is an optical waveguide composed of a substrate, a clad formed on the substrate, and a core disposed in the clad, wherein the core has a rare-earth element having a predetermined concentration distribution.
  • Element and a correction element that has at least one of the function of suppressing rare earth element class disintegration and the function of exciting the rare earth element with excitation light to broaden the signal light amplification band. is there.
  • the rare earth element may have a concentration distribution in which the concentration gradually decreases from the center to the periphery, and the concentration is uniform from the center to the periphery in the substrate plane direction, and is perpendicular to the substrate plane.
  • a density distribution may be provided in which the density gradually decreases from the center to the periphery.
  • the modifying element may be added uniformly in the core, or may be added in the core in a distribution similar to the concentration distribution of the rare earth element in the core.
  • the correction element may be any one of A 1, B, G a, In, G e, S n, B i, N, P, and Y b.
  • the concentration distribution of the rare earth element in the core is the same as the intensity distribution of light propagating through the core, the Gaussian distribution that becomes maximum at the center of the core and becomes smaller toward the periphery, It is sufficient that the ratio of the deviation from the Gaussian distribution which becomes the maximum and becomes smaller toward the periphery is within the range of any distribution within 30%.
  • the concentration distribution of the modifying element may be uniform or similar to the light intensity distribution.
  • the rare earth element may be any one of Er, Tm, Pr, and Nd.
  • the main component of the core may be any of silicon oxide, aluminum oxide, and bismuth oxide.
  • the method for manufacturing an optical waveguide according to the present invention includes a step of forming a lower clad on a substrate; and a step of forming a core containing a rare earth element and a modifying element at a high concentration in the center on the lower clad; A step of forming an upper cladding on the lower cladding and the core, wherein the modifying element has a function of suppressing clustering of the rare earth elements added to the core and a function of suppressing the rare earth elements added to the core. It was made of an element having at least one of the functions of expanding the signal light amplification band by being excited by the excitation light.
  • the step of forming the core includes a step of forming a film to be a core on the lower clad, and a step of injecting a rare earth element and a correction element into the film while scanning a focused ion beam.
  • a film formation method using a first target including a main component of the core, a second target including a rare earth element, and a third target including a correction element on the lower clad is performed.
  • the concentration of the rare earth element gradually decreases from the center of the film to the upper and lower peripheral parts
  • the concentration of the correction element gradually decreases in the film and gradually decreases from the center to the upper and lower peripheral parts.
  • a step of forming a layer having a certain concentration distribution may be provided.
  • the core may be formed by a sputtering method that changes the sputtered state of the second target and the third target, or the second target and the third target may be formed by a sputtering method.
  • the target may be formed by an ion plating method that changes the evaporation state of the target, or may be formed by an evaporation method that changes the evaporation amount of the second target.
  • the second target and the third target may be composed of the same evening target containing a rare earth element and a modifying element at the same time.
  • a first source gas containing a main component of the core, a second source gas containing a rare earth element, and a third source gas containing a correction element are introduced on the lower clad.
  • the concentration of rare earth elements gradually decreases from the center of the film to the upper and lower peripheries, and the concentration of the correction element remains constant inside the film.
  • a step may be provided for forming the density distribution so that the density distribution is one of a state and a state where the density gradually decreases from the central part to the upper and lower peripheral parts.
  • FIG. 1A is a cross-sectional view schematically illustrating a configuration example of an optical waveguide according to an embodiment of the present invention.
  • 1B and 1C are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to the embodiment of the present invention.
  • FIG. 2A and FIG. 2B are distribution diagrams showing the concentration distribution of the modifying element in the core of the optical waveguide in the example of the present invention.
  • FIG. 3A and FIG. 3B are distribution diagrams showing the concentration distribution of the modifying element in the core of the optical waveguide in the example of the present invention.
  • FIGS. 4A and 4B are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
  • FIGS. 5A and 5B are distribution diagrams showing the concentration distribution of the modifying element in the core of the optical waveguide according to another embodiment of the present invention.
  • FIG. 6A is a distribution diagram showing a distribution of light intensity in a core of an optical waveguide according to another embodiment of the present invention.
  • FIGS. 6B and 6C are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
  • FIGS. 7A and 7B are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
  • FIG. 8A and FIG. 8B are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
  • FIG. 9A, FIG. 9B, FIG. 9C, and FIG. 9D are process diagrams for explaining a method of manufacturing an optical waveguide according to the embodiment of the present invention.
  • FIG. 10 is a view for explaining a method of partially manufacturing an optical waveguide in an embodiment of the present invention. It is a perspective view.
  • FIG. 11 is a configuration diagram schematically showing a manufacturing apparatus for realizing the method of manufacturing an optical waveguide according to the embodiment of the present invention. .
  • FIG. 12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12I and 12J illustrate a method of manufacturing an optical waveguide according to another embodiment of the present invention.
  • FIG. 12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12I and 12J illustrate a method of manufacturing an optical waveguide according to another embodiment of the present invention.
  • FIG. 1A is a schematic sectional view schematically showing a configuration example of an optical waveguide according to a first embodiment of the present invention.
  • This optical waveguide is composed of a lower clad 2 formed on a substrate 1, a core 3, and an upper clad 4 formed so as to cover the core 3, and propagates in the core 3 to a region including the core 3.
  • a rare earth element for amplifying signal light is added.
  • the refractive index of the core 3 is larger than that of the lower cladding 2 and the upper cladding 4, and extends in a direction parallel to the plane of the substrate 1.
  • FIG. 1B and 1C are distribution diagrams showing the concentration distribution (profile) of a rare earth element in a cross section of the optical waveguide shown in FIG. 1A.
  • FIG. 1B shows a direction in which the core 3 is disposed in a direction perpendicular to the waveguide direction of the core 3 in a plane perpendicular to the optical waveguide direction of the core 3, that is, the substrate 1 is located downward with the information of the substrate 1.
  • the density distribution in the width direction of the core 3 is shown.
  • FIG. 1C shows the concentration distribution of the core 3 in the height direction.
  • the concentration of the rare earth element added to the core 3 was high near the center and gradually decreased toward the periphery.
  • the concentration of the rare earth element is defined as the X-axis (width direction) in the plane direction of the substrate 1 and the Y-axis (height direction) normal to the surface of the substrate 1 in a plane perpendicular to the optical waveguide direction of the core 3. In the coordinate system formed by, it gradually decreases in both the X and Y directions.
  • the concentration of the rare earth element does not need to be rapidly reduced to zero outside the core 3 and may be gradually reduced.
  • a modifying element is added together with the rare earth element.
  • the concentration distribution of A 1 and P in the core 3 is set to be substantially equal to the concentration distribution of Er. Good.
  • the substrate 1 is a silicon substrate.
  • Lower clad 2 is the also constructed from S I_ ⁇ 2 having a thickness of 1 5 m
  • the upper cladding 4 is a S i O 2 of boron and phosphorus having a thickness of 1 0 is added (BPSG).
  • the core 3 is a square having a cross section of 2 m square and is composed mainly of a silicon-based material such as silicon oxide to which erbium (Er) is added as a rare earth element, aluminum oxide, bismuth oxide, and the like. It was done.
  • the concentration of Er added to Core 3 reaches a maximum near the center of Core 3 (1 ⁇ 10 20 atoms Z cm 3 ) and gradually decreases toward the periphery of Core 3. are doing.
  • the concentration of Er gradually decreases to 1 ⁇ 10 19 atoms / cm 3 at the interface between the core 3 and the clad.
  • the concentration of Er decreases in both the X and Y directions.
  • the rare earth element concentration distribution is high at the center of the core, and does not become zero on the way to the periphery, but decreases so as to decrease.
  • the excitation light introduced into the optical waveguide composed of the core 3 has an intensity distribution in the core 3 of the waveguide, the intensity is strong at the center, the intensity decreases near the core 3, and the intensity around the core 3 is reduced. Part of the lower cladding 2 and upper cladding 4 also penetrate. Since the amplification of the optical signal is caused by the relaxation of the energy of the rare earth element excited by the excitation light, it is preferable to excite all the added rare earth elements for the most efficient optical amplification. If some of the rare earth elements added to the core 3 are not excited, they contribute to the absorption of the signal light and contribute to the attenuation of the optical signal, and thus become an inhibiting factor of the optical amplification.
  • the distribution of the rare earth element in the core 3 is configured to be higher toward the center of the core 3 and decrease toward the periphery of the core 3, and the excitation light inside the core 3 is reduced. It corresponded to the light intensity distribution.
  • the concentration distribution of the rare earth element in the core 3 may be substantially Gaussian distribution.
  • the concentration distribution range may have an appropriate width and deviate from the Gaussian distribution so as to cope with a case where the light intensity distribution deviates from the Gaussian distribution due to deformation of the core 3 or the like. The gain is reduced by the deviation, but it is not a significant decrease.
  • the rare earth element added to the core 3 is not limited to Er, but may be thulium (Tm), plunge (Pr), neodymium (Nd), or any other element capable of amplifying signal light by excitation radiation. Or a plurality of them may be added.
  • Tm thulium
  • Pr plunge
  • Nd neodymium
  • the above Er concentration, substrate and cladding materials, dimensions and the like are examples of the present invention and are not limited thereto.
  • the elements to be added to the core 3 are as follows: £ 1 "and 8 1, P are added in a uniform concentration distribution in the core 3.
  • the concentration of A 1 is determined by the S i in the core 3 consisting of S i ⁇ 2.
  • the concentration of P was 5% with respect to the Si in core 3.
  • a 1 was added to the S i 0 2 suppresses cluster Ichika when doped with a rare earth element at high concentration, there is the action of both expanding the amplification wavelength band.
  • elements having such a function instead of A1, boron (B), gallium (Ga), indium (In), germanium (Ge), tin (Sn), bismuth (Bi), nitrogen (N ), Phosphorus (P), itridium (Yb) and oxides thereof, and these may be added to the core 3.
  • Each element has both functions, although the degree of effect on both functions is different.
  • One or two or more of these elements for suppressing clustering and for improving the amplification band may be added to the core 3, and other elements having the same function may be added. It may be added.
  • the above Er concentration, the modifying element to be added, the material and dimensions of the substrate and the cladding are merely examples, and are not limited thereto.
  • the Er concentration that can be added without clustering was doubled compared to the case without the correction element, and a waveguide gain of 2. O dBZcm was obtained. An amplification band of 1 dBZ cm or more was obtained at 30 nm or more.
  • the concentration distribution of A 1, ⁇ added to the core 3 together with Er in the core 3 may be substantially equal to the concentration distribution of Er.
  • the concentration distribution of A 1 in core 3 is such that, in the vicinity of the center of core 3, a concentration of 10% is added to S i in S i 0 2 , and the concentration distribution of P is In the vicinity of the center, it is set to 5% of S i ⁇ .
  • the inventors have found that the corrected element concentration distribution does not necessarily need to be exactly proportional to the rare earth element concentration distribution, and that the corrected element concentration distribution is 30% or less of the proportional value of the rare earth element concentration distribution. It has been confirmed that the effect does not deteriorate within the error range.
  • the waveguide gain of the optical waveguide was increased to 2.5 dB / cm, compared to 2.0 dB / cm when a correction element such as A1, P was added uniformly in the core 3. .
  • the optical waveguide has the configuration shown in FIG. 1A.
  • the concentration distribution of the rare earth element in the core 3 was as shown in FIGS. 4A and 4B.
  • the concentration distribution in the width direction of the core 3, that is, in the substrate plane direction was made uniform as shown in FIG. 4A.
  • the concentration distribution in the height direction of the core 3, that is, the direction perpendicular to the plane of the substrate was high near the center of the core 3 and gradually decreased toward the periphery as shown in FIG. 4B.
  • the correction elements added together with the rare earth elements were A1 and P, and the concentration distribution was uniform in the X and Y directions as shown in Figs. 2A and 2B.
  • a 1 and P may be added in the same manner as the concentration distribution of the rare earth element.
  • the concentration distribution in the plane direction of the substrate is made uniform as shown in FIG. That is, the concentration distribution in the direction perpendicular to the substrate plane may be high near the center of the core 3 and gradually decrease toward the periphery, as shown in FIG. 5B.
  • the substrate 1 is a silicon substrate
  • the lower cladding 2 has been constructed from the S i 0 2 having a thickness of 1 5 m
  • the upper cladding 4 Is SiO 2 (BPSG) with a thickness of 10 m to which boron and phosphorus are added.
  • the core 3 has a square cross section of 2 m square, and is a silica-based material to which Er is added as a rare earth element. It is composed of fees.
  • the Er concentration added to the silica-based core 3 was uniform in the X direction (width direction). Also, in the Y direction (height direction), the maximum is set near the center of the core 3 (1 ⁇ 10 20 atoms Z cm 3 ), and the density gradually decreases toward the periphery of the core 3. At the cladding interface, it was gradually reduced to 1 ⁇ 10 19 atoms Z cm 3 .
  • the correction elements to be added to core 3 are added at a uniform concentration distribution in core 3 using A 1 and P.
  • the concentration of A 1 is 10% added to S i in S i 0 2 constituting core 3, and the concentration of P is 5% to S i in S i 0 2. I made it.
  • the waveguide gain of the optical waveguide was 1.5 dB / cm.
  • the concentration distribution of A 1 and P added together with Er to the core 3 in the core 3 may be substantially equal to the concentration distribution of Er.
  • the concentration distribution of Al and P in the core 3 may be uniform in the X direction of the core 3 and gradually decrease toward the periphery in the Y direction.
  • the waveguide gain of the optical waveguide was 2.2 dB / cm.
  • the inventors have found that the corrected element concentration distribution does not necessarily need to be exactly proportional to the rare earth element concentration distribution, and that the corrected element concentration distribution is 30% or less of the proportional value of the rare earth element concentration distribution. It has been confirmed that the effect does not deteriorate within the error range. ⁇ Example 3>
  • the concentration distribution of the rare earth element in the core 3 was as shown in FIGS. 6B and 6C.
  • the concentration distribution in the height direction of the core 3 is increased near the center of the core 3 as shown in FIG. 6C in accordance with the light intensity distribution propagating in the core 3 as shown in FIG. 6A.
  • the state gradually decreases toward the periphery.
  • the concentration distribution of the rare earth element in the width direction of the core 3 was made uniform toward the periphery as shown in FIG. 6B.
  • the concentration distributions of the modified elements A1 and P are uniform in the core 3 as shown in Figs. 2A and 2B, and similar to those of the rare earth elements as shown in Figs. 6B and 6C. In the distribution Just fine.
  • Substrate 1 is a silicon substrate
  • lower clad 2 is made of Si 2 having a thickness of 15 m
  • the cladding 4 is Si 2 (BP SG) with a thickness of 10 zm to which boron and phosphorus are added.
  • the core 3 has a square shape with a cross section of 2 m square, and is made of a silicon-based material to which Er is added as a rare earth element.
  • the Er concentration added to the silica-based core 3 is uniform in the X direction, and is maximum (1 ⁇ 1020 atoms Zcm 3 ) near the center of the core 3 in the Y direction.
  • the configuration is such that it decreases in proportion to the intensity distribution of the signal light toward the periphery of the core 3.
  • concentration distributions of A l and P in the case of A 1, a concentration of 10% is added to S i in S i ⁇ 2 near the center of core 3, and the concentration distribution of P is In the vicinity of the center, it is 5% of S i in S i 0 2 .
  • the distribution is uniform in the core 3, the distribution is at this concentration, and when the distribution is similar to the rare earth element distribution, the distribution is similar to the distribution of the excitation light in the Y direction.
  • the waveguide gain of the optical waveguide was 1.6 dBZcm when the concentration distribution of A 1 and P was uniform in the core, and 2.3 dBZcm was obtained when the concentration distribution was similar to the excitation light intensity. .
  • the rare earth concentration distribution is uniform in the X direction and similar to the excitation light intensity in the Y direction, but may be similar to the excitation light intensity in both directions.
  • the concentration distribution of the rare earth element in the height direction of the core 3 is high near the center of the core 3 as shown in FIG. The state was reduced to On the other hand, the concentration distribution of the rare earth element in the width direction of the core 3 was made uniform toward the periphery as shown in FIG. 7A. Therefore, the optical waveguide according to the present embodiment has substantially the same effect as the embodiment having the concentration distributions shown in FIGS. 6B and 6C.
  • the concentration distributions of the correction elements A 1 and P may be uniform within the core 3 as shown in FIGS. 2A and 2B, and similar to those of the rare earth elements as shown in FIGS. 7A and 7B. Is also good.
  • Substrate 1 is a silicon substrate
  • lower clad 2 is made of Si 2 having a thickness of 15 m
  • the cladding 4 is made of Si 2 (BPSG) doped with boron and phosphorus to a thickness of 10 / m.
  • the core 3 is a square having a cross section of 2 zm square and made of a silicic material to which Er is added as a rare earth element.
  • the Er concentration added to the silica-based core 3 is made uniform in the X direction, and is maximum (1 ⁇ 1020 atoms / cm 3 ) near the center of the core 3 in the Y direction. It was made to decrease in a Gaussian distribution toward the periphery of the core 3, and at the interface between the core 3 and the cladding, it became 1 ⁇ 1019 atoms Z cm 3 .
  • a 1 for the concentration distribution of P, in the case of A 1, in the vicinity of the core 3 around which the addition of a concentration of 10% with respect to S i in S i 0 2, the concentration distribution of P, the core 3 in the vicinity of the center is 5% relative to S i in S I_ ⁇ 2. If it is uniform in the core 3, it is distributed at this concentration, and if it is similar to the rare earth element distribution, it becomes Gaussian.
  • the waveguide gain of the optical waveguide is 1.6 dB / cm when the concentration distribution of A 1 and P is uniform in the core, and 2.3 dBZcm when the concentration distribution is similar to the excitation light intensity. was done.
  • the rare earth concentration distribution is uniform in the X direction and Gaussian in the Y direction, but may be Gaussian in both directions.
  • the present inventors have confirmed that the Er concentration distribution does not necessarily have to be exactly Gaussian distribution.
  • I have. 8A and 8B show examples in which the error range from the Gaussian distribution is in the X and Y directions. As shown in the X direction in Fig. 8A and the Y direction in Fig. 8B, it has been confirmed that the effect of the gain increase does not deteriorate if the error is within ⁇ 30% of the Gaussian distribution.
  • the dotted lines indicate distributions that increase by + 30% and decrease by 30%, respectively, with respect to the Gaussian distribution, and may be a rare earth element distribution that changes as indicated by the solid lines.
  • the density is changed in both the X and Y directions. However, the density may be made uniform in one of the directions.
  • a method of manufacturing the optical waveguide in the above-described embodiment, particularly, the waveguide portion will be described. Will be described. First, as shown in FIG. 9A, a lower clad 2 is formed on a substrate 1, and then, as shown in FIG. 9B, a film 3a to be a core 3 is formed on the lower clad 2.
  • the film 3a is processed by E), and the core 3 is formed on the lower clad 2 as shown in FIG. 9C.
  • the optical waveguide is completed.
  • a CVD method for the formation of each layer, for example, a sputtering method, an evaporation method, a flame deposition method, or the like may be used.
  • an efficient optical amplifier is realized by adding a rare earth element or a correction element into the core 3 with an appropriate concentration distribution.
  • each element may be added by a focused ion beam.
  • a focused ion beam for example, the Er element is ionized into an ion beam, and this ion beam is irradiated inside the core 3 while scanning, thereby implanting the ionized Er into the core 3 with an appropriate energy. .
  • a concentration distribution of Er in the core 3 can be formed.
  • An Er element or an oxide thereof may be used as an ion beam.
  • A1 is used as a modifying element, the A1 element or its oxide molecule can be used as an ion beam.
  • the concentration of the additive is controlled by adjusting the concentration of the additive to be ionized. By controlling the convergence position of the ion beam and the addition concentration, the concentration X-direction distribution of the rare earth element or the correction element added to the core 3 is controlled. Further, by controlling the beam energy, it is possible to control the Y-direction distribution of the additive concentration.
  • the core 3 is buried in the upper cladding 4 to obtain light.
  • An optical waveguide serving as an amplifier can be formed.
  • the same method as for the lower cladding 2 and the core 3 can be used for forming the upper cladding 4.
  • the core 3 may be manufactured by a sputter method using a sputter device schematically shown in FIG.
  • the film 3a shown in FIG. 9B is formed by the sputtering device shown in FIG.
  • the sputtering in the evening apparatus is provided with a target of S I_ ⁇ the second evening one rodents Bok and E r 2 ⁇ 3 target and A 1 2 0 3.
  • the amount of each additive is changed in the thickness direction of the film 3a by changing the amount of sputter at each get while the film 3a is being formed. it can.
  • the concentration of each element is uniform in the X direction (the direction of the film surface). Since different sunsets are used in the Y direction (film thickness direction), it is possible to realize a desired density change such as the density distribution described in each of the above-described embodiments.
  • an oxide target of each element is used, but an element target instead of an oxide may be used.
  • the film forming method is not limited to the sputtering method, and other methods such as a CVD method, an ion plating method, a vapor deposition method, and a flame deposition method can be used. In any case, the elements Er and A1 can be supplied from different raw materials, and the supply amount can be changed as the film is formed to achieve a desired concentration distribution.
  • FIG. 1 2 A forming a lower clad 2 on the substrate 1, and then, as shown in FIG. 1 2 B, £ 1 "Ya £]: 2 0 3, A 1 and A 1 A high-concentration layer 13a containing a high concentration of ⁇ 3 is formed
  • the high-concentration layer 13a is formed into a rectangular cross section by using a known photolithography technique and an etching technique such as RIE.
  • the core 3 is formed on the lower clad 2 as shown in FIG. 12C.
  • an upper clad 4 is formed so as to cover the core 3.
  • the lower cladding 2, the high concentration layer 13a, and the upper cladding 4 can be formed by, for example, a CVD method, a sputtering method, various vapor deposition methods, a flame deposition method, or the like.
  • the thickness of the upper cladding 4 is adjusted so that the core 3 is substantially at the center of the layer composed of the lower cladding 2 and the upper cladding 4.
  • the concentration of the rare earth element and the modifying element uniformly added to the core 3 at the time of FIG. 12D is high near the center of the core 3 and gradually increases in the X and Y directions toward the periphery of the core 3. The structure is reduced.
  • the core 3 was formed by processing the high concentration layer 13a, but the present invention is not limited to this.
  • the core may be formed as follows. First, as shown in FIG. 12F, a lower cladding 2 a is formed on a substrate 1. The lower cladding 2a is formed, for example, to have a total thickness of the lower cladding 2 and the high concentration layer 13a shown in FIG. 12B. Next, a groove is formed in the lower clad 2a as shown in FIG. 12G by using a known photolithography technique and an etching technique such as RIE.
  • an upper clad 4 a is formed so as to cover the core 3.
  • the lower cladding 2a, the above-mentioned film, and the upper cladding 4a can be formed by, for example, a CVD method, a sputtering method, various vapor deposition methods, a flame deposition method, or the like.
  • the thickness of the upper cladding 4a is adjusted such that the core 3 is substantially at the center of the layer composed of the lower cladding 2a and the upper cladding 4a.
  • a high-temperature annealing treatment is performed to diffuse the additives in the core 3 to the periphery.
  • the concentration of the rare earth element and the correction element uniformly added to the core 3 at the time of Fig. 12I is high near the center of the core 3 and gradually increases in the X and Y directions toward the periphery of the core 3. The structure is reduced.
  • the upper cladding 4 (upper cladding 4 a)
  • a high-temperature heat treatment for diffusion of Er and A 1 was performed, but after forming a low-concentration layer surrounding the core 3.
  • the upper clad may be formed after heat treatment at a high temperature to diffuse Er and A1.
  • a high-concentration layer 13 a made of 3 ⁇ 10 20 atoms Z cm 3 , Si 1 added with 1 O wt% of 81 and 12 wt% of P, and To form This was processed to form a core 3 with a cross-sectional dimension of 0.8 x 0.8 m, and after forming the upper cladding 4, an annealing process of 100 in oxygen atmosphere was performed for 3 hours.
  • An optical waveguide having the core having the concentration distribution shown in FIGS. 1B and 1C can be obtained.
  • the rare earth element in the core is provided with a concentration distribution such that the concentration decreases toward the periphery, so that the optical signal is mainly amplified at the center of the core. Become.
  • an excellent effect that higher gain can be obtained in the waveguide type optical amplifier can be obtained.
  • the optical waveguide using the planar waveguide according to the present invention is suitable for use in long-distance wavelength multiplex communication.

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Abstract

An optical waveguide type amplifier which has a core (3) containing a rare earth element having a concentration distribution such that the concentration is high in a central portion of the core and become gradually lower toward the perimeter and also a modifying element for preventing the rare earth element from forming a cluster and for expanding the wavelength region for a light capable of being amplified having a concentration distribution similar to that of the rare earth element, wherein the concentration of the rare earth element is gradually decreased both in the X direction and the Y direction in a coordinate system formed, in a plane perpendicular to the light guiding direction of the core (3), by an X axis of the direction of the surface of a substrate (1) (the width direction of the plane) and a Y axis of the direction of the normal to the surface of a substrate (1) (the height direction of the plane). The optical waveguide type amplifier allows the achievement of an enhanced gain.

Description

光導波路及びその製造方法 発明の背景  BACKGROUND OF THE INVENTION
本発明は、 平面型導波路を用いた光導波路及びその製造方法に関し、 特にガラ スからなる導波路中に希土類を添加することで光増幅作用を備えた光導波路及び 明  The present invention relates to an optical waveguide using a planar waveguide and a method for manufacturing the same, and more particularly to an optical waveguide having an optical amplification effect by adding a rare earth element to a glass waveguide.
その製造方法に関するものである。 It relates to the manufacturing method.
細  Fine
光増幅器は、 電気回路を通さずに光を直接増幅し、 しかも広い波長範囲に渡つ て増幅するため、 近年の長距離の波長多重通信において非常に重要なデバイスと なっている。 現在は、 エルビウム等の希土類元素を添加したファイバーを用いた 光増幅器が主に使われており、 高い増幅利得や低いノィズ特性などを有した高品 質のものが提供されている。  Optical amplifiers are a very important device in recent long-distance WDM communications because they directly amplify light without passing through electric circuits and amplify over a wide wavelength range. At present, optical amplifiers using fibers doped with rare earth elements such as erbium are mainly used, and high quality amplifiers with high amplification gain and low noise characteristics are provided.
このような中で、 より小型化を目指して平面光導波路に希土類元素を添加した 光増幅器が開発されるようになってきており、 より高い利得とより広い増幅帯域 を目指した光増幅器の開発が行われている。 光増幅器の小型化と高利得化を両立 させるためには、 添加する希土類元素の濃度を大きくすればよい。  Under these circumstances, optical amplifiers with rare-earth elements added to planar optical waveguides have been developed with the aim of further miniaturization, and optical amplifiers aiming for higher gain and wider amplification band have been developed. Is being done. In order to achieve both miniaturization and high gain of the optical amplifier, the concentration of the rare earth element to be added may be increased.
光増幅器では、 外部から励起光を光増幅部に導入して希土類の電子を励起し、 信号光でそれを緩和させて誘導放出により元の信号光の強度を増大している。 こ のため、 効率よく利得を大きくするためには、 より多くの励起準位を導波路の中 に設ければよい。 従って、 励起準位を作る源となるエルビウム等の希土類元素を より多く導波路内に導入することで、 小型化と高利得化とが両立できるようにな る。  In an optical amplifier, pumping light is introduced from the outside into an optical amplifier to excite rare-earth electrons, which are relaxed by signal light, and the intensity of the original signal light is increased by stimulated emission. Therefore, in order to increase the gain efficiently, more pump levels should be provided in the waveguide. Therefore, by introducing more rare earth elements such as erbium as a source for generating an excitation level into the waveguide, both miniaturization and high gain can be achieved.
ところが、 希土類は、 高濃度に導波路ガラス内に添加された場合に、 クラスタ —化する特性がある。 希土類がクラスター化すると、 励起準位が変化し、 所望の 波長での励起に寄与する希土類元素の数が実質的に減少し、 増幅利得が低下する。 このため、 小型化と高利得化とを両立させるためには、 クラスターを抑制した状 態で、 導波路ガラス内の希土類濃度を高くすればよいことになる。 光増幅器に要求される重要な特性として、 高い利得とともに、 増幅波長帯域が 広いことがあげられる。 波長多重通信においては、 例えば 0 . 8 n m間隔で 4 0 種の波長の光信号が使用され、 合計で 3 2 n mの波長帯域が使用されていること になる。 このような波長多重通信で用いられる光増幅器では、 3 2 n m以上の範 囲の帯域で利得を増幅する機能が要求される。 However, rare earths have the property of clustering when added at high concentrations into the waveguide glass. When the rare earths are clustered, the excitation level changes and the number of rare earth elements contributing to excitation at the desired wavelength is substantially reduced, reducing the amplification gain. Therefore, in order to achieve both miniaturization and high gain, it is only necessary to increase the rare-earth concentration in the waveguide glass while suppressing clusters. Important characteristics required for optical amplifiers include high gain and a wide amplification wavelength band. In wavelength multiplex communication, for example, optical signals of 40 kinds of wavelengths are used at 0.8 nm intervals, and a total of 32 nm wavelength band is used. An optical amplifier used in such wavelength division multiplexing communication is required to have a function of amplifying a gain in a band of 32 nm or more.
ここで、 添加された希土類のクラス夕一化抑制と光増幅器の広帯域化のために、 導波路ガラスに希土類以外の元素を導入した例が報告されている （文献 1 ：特開 平 9— 1 0 5 9 6 5号公報） 。 文献 1においては、 希土類以外の少なくとも 2つ の元素を導波路のコアに添加している。 この 2つの元素は、 し&ゃ八'1ゃ0 な どの、 I I I B属， I V B属， I I I A属の元素である。 これらの元素は、 希土 類元素と同時にコア中に存在することにより、 希土類のクラスター化を抑制し、 励起準位をブロードにして増幅波長帯域を拡大する効果が得られる。 これらの元 素は、 コア中に均一に添加されている。  Here, there has been reported an example in which an element other than the rare earth element is introduced into the waveguide glass to suppress the disintegration of the added rare earth class and broaden the bandwidth of the optical amplifier (Reference 1: Japanese Unexamined Patent Application Publication No. 9-11-1). No. 0 595 6). In Reference 1, at least two elements other than rare earths are added to the core of the waveguide. These two elements are elements of the genus IIB, IVB, and IIA, such as ゃ & ゃ '1 ゃ 0. The presence of these elements in the core at the same time as the rare-earth elements suppresses the clustering of the rare-earth elements, broadens the excitation level, and broadens the amplification wavelength band. These elements are uniformly added in the core.
また、 希土 fS元素をコアの中心層のみに添加することで、 広帯域化と高い増幅 効果とを得ようとする技術も提案されている （文献 2 ：特開平 4— 3 5 9 2 3 0 号公報） 。 文献 2に示された技術においては、 クラスタ一化抑制や広帯域化する ための助成元素も同時にコアの中心層のみに添加し、 これらの上下のコア部には 希土類元素も助成元素も導入しないようにしている。 これは、 希土類元素を励起 する励起光強度分布がコア中心部で高いため、 このコア中心部分に選択的に希土 類を添加することで、 励起効率を高めて高利得化を図るようにしたものである。 光強度の弱い領域に多くの E r元素があってもこの領域に添加されているすべ ての E r元素は、 励起しきれないため、 逆に光の吸収に寄与してしまう。 このた め、 上記技術においては、 光強度の強い中心部以外には E rを添加していないよ うにしている。 また、 助成元素は、 希土類含有層にあればよく、 上記技術では、 コアの中心部以外の領域には、 光吸収に寄与してしまうために添加しないように している。  Also, a technique has been proposed in which a rare-earth fS element is added only to the central layer of the core to obtain a wider band and a higher amplification effect (Reference 2: Japanese Patent Application Laid-Open No. 4-3599230). No.). In the technology shown in Reference 2, an auxiliary element for suppressing cluster unification and broadening the band is also added only to the central layer of the core at the same time, and neither the rare earth element nor the auxiliary element is introduced into the upper and lower core portions. I have to. This is because the intensity distribution of the excitation light for exciting the rare earth element is high at the center of the core, and the rare earth is selectively added to the center of the core to increase the excitation efficiency and increase the gain. Things. Even if there are many Er elements in a region where the light intensity is weak, all the Er elements added to this region cannot be excited enough and conversely contribute to light absorption. For this reason, in the above technique, Er is not added except for the central part where the light intensity is strong. Further, the assisting element only needs to be in the rare earth-containing layer, and in the above technique, it is not added to a region other than the center of the core because it contributes to light absorption.
また、 希土類元素をコアの中で分布させ、 励起光率を高めようとする技術も提 案されている （文献 3 ：特開平 6— 2 8 1 9 7 7号公報） 。 文献 3に示された技 術においては、 コア中心部で高濃度に、 コア周辺部では低濃度に E rが添加され ている。 これは、 E r元素を励起する励起光強度分布がコア中心部で高く周辺で 弱いため、 コア中心部に多く周辺部に少なく E rを添加することで、 励起光率を 高めて高利得化を図るようにしたものである。 この技術によれば、 最高濃度と最 低濃度の比が 2倍以上となるように、 コア内での E rの濃度を分布させている。 ところで、 より多くの機能をより小型な装置で実現することが要求されている 中で、 上述した光増幅器も、 より小型化することが要求されている。 上述したよ うな導波路型の光増幅器では、 導波路方向の単位長さ当たりの利得をより大きく することで光増幅器を短く小型化するようにしている。 このように、 近年の小型 化の要求に対応するためには、 光増幅器のさらなる高利得化が必要となっている。 発明の概要 In addition, a technique for distributing rare earth elements in a core to increase the excitation light efficiency has been proposed (Reference 3: Japanese Patent Application Laid-Open No. 6-281977). In the technology shown in Reference 3, Er is added at a high concentration at the center of the core and at a low concentration at the periphery of the core. ing. This is because the excitation light intensity distribution that excites the Er element is high at the center of the core and weak at the periphery, so adding a large amount of Er at the center of the core and a small amount of Er around the core increases the excitation light rate and increases the gain. It is made to aim at. According to this technology, the concentration of Er in the core is distributed so that the ratio of the highest concentration to the lowest concentration is more than twice. By the way, while it is required to realize more functions with a smaller device, the above-mentioned optical amplifier is also required to be smaller. In the waveguide-type optical amplifier described above, the gain per unit length in the waveguide direction is increased to shorten and reduce the size of the optical amplifier. Thus, in order to meet the recent demand for miniaturization, it is necessary to further increase the gain of the optical amplifier. Summary of the Invention
本発明は、 以上のような問題点を解消するためになされたものであり、 導波路 型の光増幅器においてより高い利得が得られるようにすることを目的とする。 本発明に係る光導波路は、 基板と、 基板上に形成されたクラッドと、 クラッド 中に配置されたコアとから構成された光導波路であって、 コアには、 所定の濃度 分布を備えた希土類元素と、 希土類元素のクラス夕一化を抑制する機能、 および 希土類元素を励起光で励起して信号光の増幅帯域を広げる機能のうち少なくとも 一方を備えた修正元素とが添加されているものである。  The present invention has been made to solve the above problems, and has as its object to obtain a higher gain in a waveguide-type optical amplifier. An optical waveguide according to the present invention is an optical waveguide composed of a substrate, a clad formed on the substrate, and a core disposed in the clad, wherein the core has a rare-earth element having a predetermined concentration distribution. Element and a correction element that has at least one of the function of suppressing rare earth element class disintegration and the function of exciting the rare earth element with excitation light to broaden the signal light amplification band. is there.
ここで、 希土類元素は、 中心部より周辺部にかけて徐々に濃度が減少する濃度 分布を備えていてもよく、 基板平面方向には中心部より周辺部にかけて濃度が均 一であり、 基板平面に垂直な方向には中心部より周辺部にかけて徐々に濃度が減 少する濃度分布を備えていてもよい。  Here, the rare earth element may have a concentration distribution in which the concentration gradually decreases from the center to the periphery, and the concentration is uniform from the center to the periphery in the substrate plane direction, and is perpendicular to the substrate plane. In any direction, a density distribution may be provided in which the density gradually decreases from the center to the periphery.
また、 修正元素は、 コア内に均一に添加されていてもよく、 コア内の希土類元 素の濃度分布と同様の分布でコア内に添加されていてもよい。 また、 修正元素は、 A 1 , B , G a , I n , G e， S n , B i , N， P , Y bの何れかであればよい。 この光導波路において、 コアにおける希土類元素の濃度分布は、 コアを伝搬す る光の強度分布と同様の分布、 コアの中心部で最大となり周辺部に行くほど小さ くなるガウス分布、 コアの中心部で最大となり周辺部に行くほど小さくなるガウ ス分布からの偏差の割合が士 3 0 %以内の分布の何れかの分布の範囲であればよ い。 修正元素の濃度分布は、 均一でも光強度分布と同様の分布であってもよい。 また、 光導波路において、 希土類元素は、 E r， Tm, P r， N dの何れかで あればよい。 また、 コアの主な成分は、 酸化シリコン， 酸化アルミニウム， 酸化 ビスマスの何れかであればよい。 Further, the modifying element may be added uniformly in the core, or may be added in the core in a distribution similar to the concentration distribution of the rare earth element in the core. The correction element may be any one of A 1, B, G a, In, G e, S n, B i, N, P, and Y b. In this optical waveguide, the concentration distribution of the rare earth element in the core is the same as the intensity distribution of light propagating through the core, the Gaussian distribution that becomes maximum at the center of the core and becomes smaller toward the periphery, It is sufficient that the ratio of the deviation from the Gaussian distribution which becomes the maximum and becomes smaller toward the periphery is within the range of any distribution within 30%. The concentration distribution of the modifying element may be uniform or similar to the light intensity distribution. In the optical waveguide, the rare earth element may be any one of Er, Tm, Pr, and Nd. The main component of the core may be any of silicon oxide, aluminum oxide, and bismuth oxide.
本発明に係る光導波路の製造方法は、 基板上に下クラッドを形成する工程と、 下クラッド上に、 中心部に高濃度に希土類元素及び修正元素が含まれたコアを形 成する工程と、 下クラッド及びコア上に上クラッドを形^する工程とを備えるよ うにし、 修正元素は、 コアに添加された希土類元素のクラスタ一化を抑制する機 能、 およびコアに添加された希土類元素を励起光で励起して信号光の増幅帯域を 広げる機能の少なくとも一方を備えた元素からなるものとした。  The method for manufacturing an optical waveguide according to the present invention includes a step of forming a lower clad on a substrate; and a step of forming a core containing a rare earth element and a modifying element at a high concentration in the center on the lower clad; A step of forming an upper cladding on the lower cladding and the core, wherein the modifying element has a function of suppressing clustering of the rare earth elements added to the core and a function of suppressing the rare earth elements added to the core. It was made of an element having at least one of the functions of expanding the signal light amplification band by being excited by the excitation light.
ここで、 コアを形成する工程は、 下クラッド上にコアとなる膜を形成する工程 と、 膜に、 収束イオンビームを走査しながら希土類元素及び修正元素を注入し、 この希土類元素及び修正元素がコアの中心部より周辺部にかけて徐々に濃度が減 少する濃度分布を備えた状態とする工程とを備えるようにしてもよい。  Here, the step of forming the core includes a step of forming a film to be a core on the lower clad, and a step of injecting a rare earth element and a correction element into the film while scanning a focused ion beam. A step of providing a concentration distribution in which the concentration gradually decreases from the central portion to the peripheral portion of the core.
または、 下クラッド上に、 コアの主たる成分を含む第 1のターゲットと、 希土 類元素を含む第 2のターゲットと、 修正元素を含む第 3の夕一ゲッ卜とを用いた 成膜方法により、 希土類元素の濃度が膜の中央部より上下の周辺部にかけて徐々 に減少し、 修正元素の濃度が膜の内部で一定の状態および中央部より上下の周辺 部にかけて徐々に減少する状態の何れかとなる濃度分布を備えるように形成する 工程を備えるようにしてもよい。 このコアを形成する工程では、 第 2のターゲッ ト及び第 3の夕一ゲッ卜のスパッ夕状態を変化させるスパッタリング法により形 成するようにしてもよいし、 第 2の夕一ゲット及び第 3のターゲッ卜の蒸発状態 を変化させるイオンプレーティング法により形成するようにしてもよいし、 第 2 の夕一ゲットの蒸発量を変化させる蒸着法により形成するようにしてもよい。 ま た、 第 2のターゲットと第 3のターゲットは、 希土類元素と修正元素とを同時に 含む同一の夕一ゲッ卜から構成されたものを用いてもよい。  Alternatively, a film formation method using a first target including a main component of the core, a second target including a rare earth element, and a third target including a correction element on the lower clad is performed. However, the concentration of the rare earth element gradually decreases from the center of the film to the upper and lower peripheral parts, and the concentration of the correction element gradually decreases in the film and gradually decreases from the center to the upper and lower peripheral parts. A step of forming a layer having a certain concentration distribution may be provided. In the step of forming the core, the core may be formed by a sputtering method that changes the sputtered state of the second target and the third target, or the second target and the third target may be formed by a sputtering method. The target may be formed by an ion plating method that changes the evaporation state of the target, or may be formed by an evaporation method that changes the evaporation amount of the second target. In addition, the second target and the third target may be composed of the same evening target containing a rare earth element and a modifying element at the same time.
また、 コアを形成する工程は、 下クラッド上に、 コアの主たる成分を含む第 1 のソースガスと、 希土類元素を含む第 2のソースガスと、 修正元素を含む第 3の ソースガスとを導入する化学的気相成長法により、 希土類元素の濃度が膜の中央 部より上下の周辺部にかけて徐々に減少し、 修正元素の濃度が膜の内部で一定の 状態および中央部より上下の周辺部にかけて徐々に減少する状態の何れかとなる 濃度分布を備えるように形成する工程を備えるようにしてもよい。 In the step of forming the core, a first source gas containing a main component of the core, a second source gas containing a rare earth element, and a third source gas containing a correction element are introduced on the lower clad. , The concentration of rare earth elements gradually decreases from the center of the film to the upper and lower peripheries, and the concentration of the correction element remains constant inside the film. A step may be provided for forming the density distribution so that the density distribution is one of a state and a state where the density gradually decreases from the central part to the upper and lower peripheral parts.
さらに、 コアを加熱して希土類元素及び修正元素を拡散させることにより、 希 土類元素及び修正元素がコアの中心部より周辺部にかけて徐々に濃度が減少する 濃度分布を備えた状態とする工程を備えるようにしてもよい。  Further, a step of heating the core to diffuse the rare-earth element and the modifying element to provide a state in which the rare-earth element and the modifying element have a concentration distribution in which the concentration gradually decreases from the central portion to the peripheral portion of the core. It may be provided.
図面の簡単な説明 BRIEF DESCRIPTION OF THE FIGURES
図 1 Aは、 本発明の実施例における光導波路の構成例を模式的に示す断面図で ある。  FIG. 1A is a cross-sectional view schematically illustrating a configuration example of an optical waveguide according to an embodiment of the present invention.
図 1 B、 図 1 Cは、 本発明の実施例における光導波路のコアにおける希土類元 素の濃度分布を示す分布図である。  1B and 1C are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to the embodiment of the present invention.
図 2 A、 図 2 Bは、 本発明の実施例における光導波路のコアにおける修正元素 の濃度分布を示す分布図である。  FIG. 2A and FIG. 2B are distribution diagrams showing the concentration distribution of the modifying element in the core of the optical waveguide in the example of the present invention.
図 3 A、 図 3 Bは、 本発明の実施例における光導波路のコアにおける修正元素 の濃度分布を示す分布図である。  FIG. 3A and FIG. 3B are distribution diagrams showing the concentration distribution of the modifying element in the core of the optical waveguide in the example of the present invention.
図 4 A、 図 4 Bは、 本発明の他の実施例における光導波路のコアにおける希土 類元素の濃度分布を示す分布図である。  FIGS. 4A and 4B are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
図 5 A、 図 5 Bは、 本発明の他の実施例における光導波路のコアにおける修正 元素の濃度分布を示す分布図である。  FIGS. 5A and 5B are distribution diagrams showing the concentration distribution of the modifying element in the core of the optical waveguide according to another embodiment of the present invention.
図 6 Aは、 本発明の他の実施例における光導波路のコアにおける光強度の分布 を示す分布図である。  FIG. 6A is a distribution diagram showing a distribution of light intensity in a core of an optical waveguide according to another embodiment of the present invention.
図 6 B、 図 6 Cは、 本発明の他の実施例における光導波路のコアにおける希土 類元素の濃度分布を示す分布図である。  FIGS. 6B and 6C are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
図 7 A、 図 7 Bは、 本発明の他の実施例における光導波路のコアにおける希土 類元素の濃度分布を示す分布図である。  FIGS. 7A and 7B are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
図 8 A、 図 8 Bは、 本発明の他の実施例における光導波路のコアにおける希土 類元素の濃度分布を示す分布図である。  FIG. 8A and FIG. 8B are distribution diagrams showing the concentration distribution of rare earth elements in the core of the optical waveguide according to another embodiment of the present invention.
図 9 A、 図 9 B、 図 9 C、 図 9 Dは、 本発明の実施例における光導波路の製造 方法を説明するための工程図である。  FIG. 9A, FIG. 9B, FIG. 9C, and FIG. 9D are process diagrams for explaining a method of manufacturing an optical waveguide according to the embodiment of the present invention.
図 1 0は、 本発明の実施例における光導波路の一部製造方法を説明するための 斜視図である。 FIG. 10 is a view for explaining a method of partially manufacturing an optical waveguide in an embodiment of the present invention. It is a perspective view.
図 11は、 本発明の実施例における光導波路の製造方法を実現するための製造 装置の概略を示す構成図である。 .  FIG. 11 is a configuration diagram schematically showing a manufacturing apparatus for realizing the method of manufacturing an optical waveguide according to the embodiment of the present invention. .
図 12A、 図 12B、 図 12C、 図 12D、 図 12E、 図 12 F、 図 12G、 図 12 H、 図 12 I、 図 12 Jは、 本発明の他の実施例における光導波路の製造 方法を説明するための工程図である。  12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12I and 12J illustrate a method of manufacturing an optical waveguide according to another embodiment of the present invention. FIG.
実施例の詳細な説明 Detailed description of the embodiment
<実施例 1 > <Example 1>
図 1 Aは本発明の第 1実施例における光導波路の構成例を概略的に示す模式的 な断面図である。 この光導波路は、 基板 1上に形成された下クラッド 2， コア 3， 及びコァ 3を覆うように形成された上クラッド 4から構成され、 コア 3を含む領 域にはコア 3内を伝搬する信号光を増幅するための希土類元素が添加されている。 コア 3の屈折率は下クラッド 2及び上クラッド 4よりも大きく、 基板 1平面に平 行な方向に延在している。  FIG. 1A is a schematic sectional view schematically showing a configuration example of an optical waveguide according to a first embodiment of the present invention. This optical waveguide is composed of a lower clad 2 formed on a substrate 1, a core 3, and an upper clad 4 formed so as to cover the core 3, and propagates in the core 3 to a region including the core 3. A rare earth element for amplifying signal light is added. The refractive index of the core 3 is larger than that of the lower cladding 2 and the upper cladding 4, and extends in a direction parallel to the plane of the substrate 1.
図 1 B、 図 1 Cは、 図 1 Aに示す光導波路における導波路断面の希土類元素の 濃度分布 （プロファイル） を示す分布図である。 図 1 Bは、 コア 3の光導波方向 に垂直な平面内のコア 3の導波方向に垂直な方向、 すなわち、 基板 1を下方とし て基板 1の情報にコア 3が配設されているものとしたときのコア 3の幅方向の濃 度分布を示している。 また、 図 1 Cは、 コア 3の高さ方向の濃度分布を示してい る。  1B and 1C are distribution diagrams showing the concentration distribution (profile) of a rare earth element in a cross section of the optical waveguide shown in FIG. 1A. FIG. 1B shows a direction in which the core 3 is disposed in a direction perpendicular to the waveguide direction of the core 3 in a plane perpendicular to the optical waveguide direction of the core 3, that is, the substrate 1 is located downward with the information of the substrate 1. The density distribution in the width direction of the core 3 is shown. FIG. 1C shows the concentration distribution of the core 3 in the height direction.
図 1 B、 図 1 Cに示すように、 本実施例の光導波路では、 コア 3に添加された 希土類元素の濃度を、 中心近傍で高く、 周辺に向かって徐々に減少する状態とし た。 希土類元素の濃度は、 コア 3の光導波方向に垂直な平面内の、 基板 1の面方 向の X軸 （幅方向） と基板 1の面の法線方向の Y軸 （高さ方向） とで形成される 座標系において、 X方向にも Y方向にも徐々に減少している。 希土類元素の濃度 は、 コア 3の外側では急激にゼロになる必要はなく徐々に減少していてもよい。 本実施例では、 希土類元素とともに、 修正元素も添加している。 まず A 1と P を添加しており、 この濃度分布は、 図 2A， 図 2 Bに示すように X方向， Y方向 に均一な濃度で添加した。 また、 修正元素の濃度はコアの外側では急激にゼロに なる必要はなく徐々に減少していてもよい。 加えて、 本実施例の光導波路におい ては、 図 3 A、 図 3 Bに示すように、 コア 3における A 1及び Pの濃度分布を、 E rの濃度分布にほぼ等しくなるようにしてもよい。 As shown in FIGS. 1B and 1C, in the optical waveguide of the present example, the concentration of the rare earth element added to the core 3 was high near the center and gradually decreased toward the periphery. The concentration of the rare earth element is defined as the X-axis (width direction) in the plane direction of the substrate 1 and the Y-axis (height direction) normal to the surface of the substrate 1 in a plane perpendicular to the optical waveguide direction of the core 3. In the coordinate system formed by, it gradually decreases in both the X and Y directions. The concentration of the rare earth element does not need to be rapidly reduced to zero outside the core 3 and may be gradually reduced. In this embodiment, a modifying element is added together with the rare earth element. First, A1 and P were added, and this concentration distribution was uniform in the X and Y directions as shown in Figs. 2A and 2B. Also, the concentration of the correction element suddenly becomes zero outside the core. It does not need to be, and may gradually decrease. In addition, in the optical waveguide of this embodiment, as shown in FIGS. 3A and 3B, the concentration distribution of A 1 and P in the core 3 is set to be substantially equal to the concentration distribution of Er. Good.
以下、 図 1 Aに示した光導波路の具体例について説明する。 まず、 基板 1は、 シリコン基板である。 下クラッド 2は、 膜厚 1 5 mの S i〇2から構成されたも のであり、 上クラッド 4は、 膜厚 1 0 のホウ素及びリンが添加された S i O 2 (B P S G) である。 また、 コア 3は、 断面が 2 m角の正方形であり、 希土類 元素としてエルビウム (E r ) が添加された酸化シリコンなどのシリ力系材料や、 酸化アルミニウム， 酸化ビスマスなどを主な成分として構成されたものである。 前述したように、 コア 3に添加された E rの濃度は、 コア 3の中心部付近で最 大 ( 1 X 1 0 2 0原子 Z c m3) となり、 コア 3の周辺に向かって徐々に減少して いる。 E rの濃度は、 コア 3とクラッドの境界面では、 1 X 1 0 1 9原子/ c m 3まで徐々に減少している。 また、 E rの濃度は、 X方向にも Y方向に減少してい る。 このように、 本実施例では、 希土類元素濃度分布をコア中心部では高く、 周 辺に行くに従い途中でゼロにすることはなく、 減少するように濃度分布をもたせ ている。 Hereinafter, a specific example of the optical waveguide shown in FIG. 1A will be described. First, the substrate 1 is a silicon substrate. Lower clad 2 is the also constructed from S I_〇 2 having a thickness of 1 5 m, the upper cladding 4 is a S i O 2 of boron and phosphorus having a thickness of 1 0 is added (BPSG). The core 3 is a square having a cross section of 2 m square and is composed mainly of a silicon-based material such as silicon oxide to which erbium (Er) is added as a rare earth element, aluminum oxide, bismuth oxide, and the like. It was done. As described above, the concentration of Er added to Core 3 reaches a maximum near the center of Core 3 (1 × 10 20 atoms Z cm 3 ) and gradually decreases toward the periphery of Core 3. are doing. The concentration of Er gradually decreases to 1 × 10 19 atoms / cm 3 at the interface between the core 3 and the clad. In addition, the concentration of Er decreases in both the X and Y directions. As described above, in this embodiment, the rare earth element concentration distribution is high at the center of the core, and does not become zero on the way to the periphery, but decreases so as to decrease.
コア 3により構成される光導波路に導入する励起光は、 導波路のコア 3内で強 度分布をもち、 中心は強度が強く、 コア 3の周辺ほど強度は減少し、 コア 3の周 辺の下クラッド 2， 上クラッド 4にも一部侵入している。 光信号の増幅は、 励起 光で励起された希土類元素のエネルギーの緩和により起るため、 最も効率よく光 増幅を行うためには、 添加した希土類元素がすべて励起されることが好ましい。 コア 3に添加された希土類元素の中で励起されないものがあると、 これらは、 信号光の吸収に寄与して光信号の減衰に寄与するため、 光増幅の阻害要因となる。 一方、 コア 3に添加した希土類元素が少なすぎれば、 光導波路の単位長さ当たり の増幅率が少なくなり、 増幅器が長く大型になってしまう。 ここで、 本実施の実 施例では、 前述したように、 コア 3における希土類元素の分布を、 コア 3の中心 ほど高く、 周囲に行くほど減少するように構成し、 コア 3内部の励起光の光強度 分布に対応するようにした。  The excitation light introduced into the optical waveguide composed of the core 3 has an intensity distribution in the core 3 of the waveguide, the intensity is strong at the center, the intensity decreases near the core 3, and the intensity around the core 3 is reduced. Part of the lower cladding 2 and upper cladding 4 also penetrate. Since the amplification of the optical signal is caused by the relaxation of the energy of the rare earth element excited by the excitation light, it is preferable to excite all the added rare earth elements for the most efficient optical amplification. If some of the rare earth elements added to the core 3 are not excited, they contribute to the absorption of the signal light and contribute to the attenuation of the optical signal, and thus become an inhibiting factor of the optical amplification. On the other hand, if the amount of the rare earth element added to the core 3 is too small, the amplification factor per unit length of the optical waveguide decreases, and the amplifier becomes long and large. Here, in the embodiment of the present invention, as described above, the distribution of the rare earth element in the core 3 is configured to be higher toward the center of the core 3 and decrease toward the periphery of the core 3, and the excitation light inside the core 3 is reduced. It corresponded to the light intensity distribution.
このことにより、 コア 3の周辺に近い部分では、 コア 3を導波する励起光によ り励起されない希土類元素数を減少させ、 励起光がコア 3内の端から端まで有効 に励起に寄与できるようになる。 コア 3内の光強度分布は、 基本的にはガウス分 布に近いので、 よりょくは、 コア 3における希土類元素の濃度分布が、 ほぼガウ ス分布となるようにすればよい。 また、 コア 3の変形などにより光強度分布がガ ウス分布からはずれた場合であっても対応できるように、 濃度分布範囲は、 適当 な幅を持ってガウス分布からはずれてもよい。 はずれた分だけ利得の低下が見ら れるが、 大きな低下にはならない。 As a result, the portion near the periphery of core 3 is excited by the excitation light guided through core 3. As a result, the number of rare earth elements that are not excited is reduced, and the excitation light can effectively contribute to the excitation throughout the core 3. Since the light intensity distribution in the core 3 is basically close to the Gaussian distribution, the concentration distribution of the rare earth element in the core 3 may be substantially Gaussian distribution. Also, the concentration distribution range may have an appropriate width and deviate from the Gaussian distribution so as to cope with a case where the light intensity distribution deviates from the Gaussian distribution due to deformation of the core 3 or the like. The gain is reduced by the deviation, but it is not a significant decrease.
なお、 コア 3に添加する希土類元素は、 E rに限るものではなく、 ツリウム (Tm) 、 プランジゥム （P r) 、 ネオジゥム （Nd) などの、 励起放射による 信号光の増幅作用のある元素であってもよく、 また、 それらを複数添加してもよ い。 また上記の E r濃度や基板及びクラッド材料ならびに寸法などは、 本発明の 一実施例でありこれに限るものではない。  The rare earth element added to the core 3 is not limited to Er, but may be thulium (Tm), plunge (Pr), neodymium (Nd), or any other element capable of amplifying signal light by excitation radiation. Or a plurality of them may be added. The above Er concentration, substrate and cladding materials, dimensions and the like are examples of the present invention and are not limited thereto.
コア 3に添加する元素は、 £ 1"とともに八 1 , Pをコア 3内で一様な濃度分布 で添加している。 A 1の濃度は、 S i〇2からなるコア 3中の S iに対して 10 % の濃度を添加し、 Pの濃度はコア 3中の S iに対して 5%にした。  The elements to be added to the core 3 are as follows: £ 1 "and 8 1, P are added in a uniform concentration distribution in the core 3. The concentration of A 1 is determined by the S i in the core 3 consisting of S i〇2. And the concentration of P was 5% with respect to the Si in core 3.
S i 02に添加した A 1は、 希土類元素を高濃度に添加した時のクラスタ一化を 抑制し、 増幅波長帯域を拡大する両方の働きがある。 このような働きを有する元 素として、 A 1の代わりにホウ素 （B) 、 ガリウム （Ga) 、 インジウム （I n) 、 ゲルマニウム （Ge) 、 錫 （Sn) 、 ビスマス （B i ) 、 窒素 (N) 、 リ ン （P) 、 イツトリビゥム （Yb) やこれらの酸化物などがあり、 これらをコア 3に添加するようにしてもよい。 元素により両方の働きに対する効果の程度は異 なるものの、 両方の働きをもつ。 A 1 was added to the S i 0 2 suppresses cluster Ichika when doped with a rare earth element at high concentration, there is the action of both expanding the amplification wavelength band. As elements having such a function, instead of A1, boron (B), gallium (Ga), indium (In), germanium (Ge), tin (Sn), bismuth (Bi), nitrogen (N ), Phosphorus (P), itridium (Yb) and oxides thereof, and these may be added to the core 3. Each element has both functions, although the degree of effect on both functions is different.
コア 3に対し、 これらのクラスター化抑制のための元素や増幅帯域増加のため の修正元素を 1つまたは 2つ以上添加してもよいし、 同様な機能を有するのであ ればその他の元素を添加してもよい。 上記の E r濃度， 添加する修正元素， 基板 やクラッドの材料及び寸法などは一例であり、 これらに限るものではない。  One or two or more of these elements for suppressing clustering and for improving the amplification band may be added to the core 3, and other elements having the same function may be added. It may be added. The above Er concentration, the modifying element to be added, the material and dimensions of the substrate and the cladding are merely examples, and are not limited thereto.
本実施例によると、 クラスター化せずに添加できる E r濃度は、 修正元素のな い場合と比べて 2倍となり、 導波路利得は 2. O dBZcmが得られた。 また 1 dBZ cm以上の増幅帯域は、 30 nm以上が得られた。 コア 3に E rとともに添加する A 1 , Ρのコア 3内濃度分布は、 E rの濃度分 布にほぼ等しくなるようにしてもよい。 この場合はのコア 3における A 1の濃度 分布は、 コア 3中心付近では S i 02中の S iに対して 1 0 %の濃度を添加してお り、 Pの濃度分布は、 コア 3中心付近では S i〇冲の S iに対して 5 %にしてい る。 According to the present example, the Er concentration that can be added without clustering was doubled compared to the case without the correction element, and a waveguide gain of 2. O dBZcm was obtained. An amplification band of 1 dBZ cm or more was obtained at 30 nm or more. The concentration distribution of A 1, 添加 added to the core 3 together with Er in the core 3 may be substantially equal to the concentration distribution of Er. In this case, the concentration distribution of A 1 in core 3 is such that, in the vicinity of the center of core 3, a concentration of 10% is added to S i in S i 0 2 , and the concentration distribution of P is In the vicinity of the center, it is set to 5% of S i 〇.
なお、 本実施例において、 本発明者らは、 修正元素濃度分布は必ずしも正確に 希土類元素濃度分布に比例している必要はなく、 希土類元素濃度分布の比例値に 対して土 3 0 %以下の誤差範囲であれば効果は悪化しないことを確認している。 この場合の光導波路の導波路利得は、 コア 3内に均一に A 1， Pなどの修正元素 を添加した場合の 2 . O d B / c mに対し、 2 . 5 d B / c mに増加した。  In the present embodiment, the inventors have found that the corrected element concentration distribution does not necessarily need to be exactly proportional to the rare earth element concentration distribution, and that the corrected element concentration distribution is 30% or less of the proportional value of the rare earth element concentration distribution. It has been confirmed that the effect does not deteriorate within the error range. In this case, the waveguide gain of the optical waveguide was increased to 2.5 dB / cm, compared to 2.0 dB / cm when a correction element such as A1, P was added uniformly in the core 3. .
<実施例 2 > <Example 2>
つぎに、 本発明の他の実施例について説明する。 なお、 本実施例においても、 光導波路は図 1 Aに示した構成である。  Next, another embodiment of the present invention will be described. In this embodiment, the optical waveguide has the configuration shown in FIG. 1A.
本実施例では、 コア 3内における希土類元素の濃度分布を、 図 4 A、 図 4 Bに 示すようにした。 まず、 コア 3の幅方向すなわち基板平面方向の濃度分布は、 図 4 Aに示すように、 均一な状態とした。 また、 コア 3の高さ方向、 すなわち基板 平面に垂直な方向の濃度分布は、 図 4 Bに示すように、 コア 3の中心近傍で高く、 周辺に向かって徐々に減少する状態とした。  In this example, the concentration distribution of the rare earth element in the core 3 was as shown in FIGS. 4A and 4B. First, the concentration distribution in the width direction of the core 3, that is, in the substrate plane direction, was made uniform as shown in FIG. 4A. The concentration distribution in the height direction of the core 3, that is, the direction perpendicular to the plane of the substrate, was high near the center of the core 3 and gradually decreased toward the periphery as shown in FIG. 4B.
希土類元素とともに添加する修正元素は、 A 1と Pを添加しており、 この濃度 分布は、 図 2 A， 図 2 Bに示すように X方向， Y方向に均一な濃度で添加した。 また、 希土類元素の濃度分布と同じように A 1， Pを添加してもよく、 基板平面 方向の濃度分布は、 図 5 Aに示すように、 均一な状態とし、 コア 3の高さ方向、 すなわち基板平面に垂直な方向の濃度分布は、 図 5 Bに示すように、 コア 3の中 心近傍で高く、 周辺に向かって徐々に減少してもよい。  The correction elements added together with the rare earth elements were A1 and P, and the concentration distribution was uniform in the X and Y directions as shown in Figs. 2A and 2B. A 1 and P may be added in the same manner as the concentration distribution of the rare earth element. The concentration distribution in the plane direction of the substrate is made uniform as shown in FIG. That is, the concentration distribution in the direction perpendicular to the substrate plane may be high near the center of the core 3 and gradually decrease toward the periphery, as shown in FIG. 5B.
以下、 本実施例における光導波路の具体例について説明する。 基本的には、 前 述した実施例と同様であり、 基板 1は、 シリコン基板であり、 下クラッド 2は、 膜厚 1 5 mの S i 02から構成されたものであり、 上クラッド 4は、 膜厚 1 0 mのホウ素及びリンが添加された S i O 2 (B P S G) である。 また、 コア 3は、 断面が 2 ^ m角の正方形であり、 希土類元素として E rが添加されたシリカ系材 料から構成されたものである。 Hereinafter, a specific example of the optical waveguide in the present embodiment will be described. Basically, the same as the embodiment described before mentioned, the substrate 1 is a silicon substrate, the lower cladding 2 has been constructed from the S i 0 2 having a thickness of 1 5 m, the upper cladding 4 Is SiO 2 (BPSG) with a thickness of 10 m to which boron and phosphorus are added. The core 3 has a square cross section of 2 m square, and is a silica-based material to which Er is added as a rare earth element. It is composed of fees.
以上説明したように、 本実施例では、 シリカ系のコア 3に添加する E r濃度は、 X方向 （幅方向） には均一とした。 また、 Y方向 （高さ方向） にはコア 3中心部 付近で最大 （1 X 1 0 2 0原子 Z c m3) とし、 コア 3の周辺に向かって徐々に減 少するようにし、 コア 3とクラッドの境界面では 1 X 1 0 1 9原子 Z c m3まで徐 々に減少させた。 As described above, in this example, the Er concentration added to the silica-based core 3 was uniform in the X direction (width direction). Also, in the Y direction (height direction), the maximum is set near the center of the core 3 (1 × 10 20 atoms Z cm 3 ), and the density gradually decreases toward the periphery of the core 3. At the cladding interface, it was gradually reduced to 1 × 10 19 atoms Z cm 3 .
コア 3に添加する修正元素は A 1， Pを用いてコア 3内で一様な濃度分布で添 加している。 A 1の濃度は、 コア 3を構成している S i 02中の S iに対して 1 0 %の濃度を添加し、 Pの濃度は S i 02中の S iに対して 5 %にした。 この場合の 光導波路の導波路利得は、 1 . 5 d B / c mが得られた。 The correction elements to be added to core 3 are added at a uniform concentration distribution in core 3 using A 1 and P. The concentration of A 1 is 10% added to S i in S i 0 2 constituting core 3, and the concentration of P is 5% to S i in S i 0 2. I made it. In this case, the waveguide gain of the optical waveguide was 1.5 dB / cm.
また、 コア 3に E rとともに添加する A 1， Pのコア 3内濃度分布は、 E rの 濃度分布にほぼ等しくなるようにしてもよい。 例えば、 A l， Pのコア 3内濃度 分布は、 コア 3の X方向には均一な分布とし、 Y方向には周辺に向かって徐々に 減少する状態とすればよい。 この場合のコア 3における A 1の濃度分布は、 コア 3中心付近では S i〇2中の S iに対して 1 0 %とし、 Pの濃度分布は、 コア 3中 心付近では S i〇2中の S iに対して 5 %としている。 この場合の光導波路の導波 路利得は、 2 . 2 d B / c mが得られた。 The concentration distribution of A 1 and P added together with Er to the core 3 in the core 3 may be substantially equal to the concentration distribution of Er. For example, the concentration distribution of Al and P in the core 3 may be uniform in the X direction of the core 3 and gradually decrease toward the periphery in the Y direction. The concentration of A 1 in the core 3 when distribution core 3 in the vicinity of the center and the 1 0% S i in S I_〇 2, the concentration distribution of P is in the vicinity of heart in the core 3 S I_〇 2 5% for S i in the table. In this case, the waveguide gain of the optical waveguide was 2.2 dB / cm.
なお、 本実施例において、 本発明者らは、 修正元素濃度分布は必ずしも正確に 希土類元素濃度分布に比例している必要はなく、 希土類元素濃度分布の比例値に 対して土 3 0 %以下の誤差範囲であれば効果は悪化しないことを確認している。 <実施例 3 >  In the present embodiment, the inventors have found that the corrected element concentration distribution does not necessarily need to be exactly proportional to the rare earth element concentration distribution, and that the corrected element concentration distribution is 30% or less of the proportional value of the rare earth element concentration distribution. It has been confirmed that the effect does not deteriorate within the error range. <Example 3>
つぎに、 本発明の他の実施例について説明する。  Next, another embodiment of the present invention will be described.
本実施例では、 コア 3内における希土類元素の濃度分布を、 図 6 B， 図 6 Cに 示すようにした。 本実施例では、 図 6 Aに示すようなコア 3内を伝搬する光強度 分布に合わせ、 コア 3の高さ方向の濃度分布を、 図 6 Cに示すように、 コア 3の 中心近傍で高く、 周辺に向かって徐々に減少する状態とする。 一方、 コア 3の幅 方向の希土類元素の濃度分布は、 図 6 Bに示すように、 周辺に向かって均一にし た。 修正元素の A 1， Pの濃度分布は、 図 2 A、 図 2 Bに示すように、 コア 3内 で均一な分布や、 図 6 B、 図 6 Cに示すように、 希土類元素と同様な分布にすれ ばよい。 In this example, the concentration distribution of the rare earth element in the core 3 was as shown in FIGS. 6B and 6C. In this embodiment, the concentration distribution in the height direction of the core 3 is increased near the center of the core 3 as shown in FIG. 6C in accordance with the light intensity distribution propagating in the core 3 as shown in FIG. 6A. However, the state gradually decreases toward the periphery. On the other hand, the concentration distribution of the rare earth element in the width direction of the core 3 was made uniform toward the periphery as shown in FIG. 6B. The concentration distributions of the modified elements A1 and P are uniform in the core 3 as shown in Figs. 2A and 2B, and similar to those of the rare earth elements as shown in Figs. 6B and 6C. In the distribution Just fine.
以下、 本実施例における光導波路の具体例について説明する。 本実施例におい ても前述した実施例と同様の構成であり、 基板 1は、 シリコン基板であり、 下ク ラッド 2は、 膜厚 15 mの S i〇2から構成されたものであり、 上クラッド 4は、 膜厚 10 zmのホウ素及びリンが添加された S i〇2 (BP SG) である。 また、 コア 3は、 断面が 2 m角の正方形であり、 希土類元素として E rが添加された シリ力系材料から構成されたものである。 Hereinafter, a specific example of the optical waveguide in the present embodiment will be described. This embodiment also has the same configuration as that of the above-described embodiment. Substrate 1 is a silicon substrate, lower clad 2 is made of Si 2 having a thickness of 15 m, and upper The cladding 4 is Si 2 (BP SG) with a thickness of 10 zm to which boron and phosphorus are added. The core 3 has a square shape with a cross section of 2 m square, and is made of a silicon-based material to which Er is added as a rare earth element.
ただし、 本実施例では、 シリカ系のコア 3に添加する E r濃度は、 X方向には 均一とし、 Y方向にはコア 3中心部付近で最大 （1 X 1020原子 Zcm3) とな るようにし、 コア 3の周辺に向かつて信号光の強度分布に比例して減少する構成 とした。 A l， Pの濃度分布については、 A 1の場合は、 コア 3中心付近では S i〇2中の S iに対して 10 %の濃度を添加しており、 Pの濃度分布は、 コア 3中 心付近では S i 02中の S iに対して 5 %にしている。 コア 3内で均一な場合はこ の濃度で分布し、 希土類元素分布と同様な場合は、 励起光分布の Y方向分布と同 様な分布となる。 However, in this example, the Er concentration added to the silica-based core 3 is uniform in the X direction, and is maximum (1 × 1020 atoms Zcm 3 ) near the center of the core 3 in the Y direction. The configuration is such that it decreases in proportion to the intensity distribution of the signal light toward the periphery of the core 3. Regarding the concentration distributions of A l and P, in the case of A 1, a concentration of 10% is added to S i in S i 〇 2 near the center of core 3, and the concentration distribution of P is In the vicinity of the center, it is 5% of S i in S i 0 2 . When the distribution is uniform in the core 3, the distribution is at this concentration, and when the distribution is similar to the rare earth element distribution, the distribution is similar to the distribution of the excitation light in the Y direction.
A 1 , Pの濃度分布がコア内で均一な場合の光導波路の導波路利得は、 1. 6 dBZcmが得られ、 励起光強度と同様な濃度分布の場合は 2. 3 dBZcmが 得られた。  The waveguide gain of the optical waveguide was 1.6 dBZcm when the concentration distribution of A 1 and P was uniform in the core, and 2.3 dBZcm was obtained when the concentration distribution was similar to the excitation light intensity. .
本実施例では、 希土類の濃度分布は、 X方向には均一、 Y方向には励起光強度 と同様な分布としたが、 両方向に対して励起光強度と同様な分布としてもよい。 ぐ実施例 4 >  In the present embodiment, the rare earth concentration distribution is uniform in the X direction and similar to the excitation light intensity in the Y direction, but may be similar to the excitation light intensity in both directions. Example 4>
つぎに、 本発明の他の実施例について説明する。 本実施例では、 コア 3におい て、 まず、 コア 3の高さ方向の希土類元素の濃度分布は、 図 7 Bに示すように、 コア 3の中心近傍で高く、 周辺に向かってガウス分布に従って徐々に減少する状 態とした。 一方、 コア 3の幅方向の希土類元素の濃度分布は、 図 7Aに示すよう に、 周辺に向かって均一にした。 従って、 本実施例における光導波路は、 図 6B、 図 6 Cに示す濃度分布とした実施例とほぼ同様の効果が得られる。 修正元素の A 1， Pの濃度分布は、 図 2A、 図 2 Bに示すようにコア 3内で均一な分布として もよく、 図 7A、 図 7 Bに示すように希土類元素と同様な分布としてもよい。 以下、 本実施例における光導波路の具体例について説明する。 本実施例におい ても前述した実施例と同様の構成であり、 基板 1は、 シリコン基板であり、 下ク ラッド 2は、 膜厚 15 mの S i〇2から構成されたものであり、 上クラッド 4は、 膜厚 10 /mのホウ素及びリンが添加された S i〇2 (BPSG) である。 また、 コア 3は、 断面が 2 z m角の正方形であり、 希土類元素として E rが添加された シリ力系材料から構成されたものである。 Next, another embodiment of the present invention will be described. In the present embodiment, in the core 3, the concentration distribution of the rare earth element in the height direction of the core 3 is high near the center of the core 3 as shown in FIG. The state was reduced to On the other hand, the concentration distribution of the rare earth element in the width direction of the core 3 was made uniform toward the periphery as shown in FIG. 7A. Therefore, the optical waveguide according to the present embodiment has substantially the same effect as the embodiment having the concentration distributions shown in FIGS. 6B and 6C. The concentration distributions of the correction elements A 1 and P may be uniform within the core 3 as shown in FIGS. 2A and 2B, and similar to those of the rare earth elements as shown in FIGS. 7A and 7B. Is also good. Hereinafter, a specific example of the optical waveguide in the present embodiment will be described. This embodiment also has the same configuration as that of the above-described embodiment. Substrate 1 is a silicon substrate, lower clad 2 is made of Si 2 having a thickness of 15 m, and upper The cladding 4 is made of Si 2 (BPSG) doped with boron and phosphorus to a thickness of 10 / m. The core 3 is a square having a cross section of 2 zm square and made of a silicic material to which Er is added as a rare earth element.
本実施例では、 シリカ系のコア 3に添加する E r濃度は、 X方向には均一とな るようにし、 Y方向にはコア 3中心部付近で最大 （1 X 1020原子/ cm3) と なるようにし、 コア 3の周辺に向かってガウス分布状に減少するようにし、 コア 3とクラッドの境界面では 1 X 1019原子 Z cm3になるようにした。 In this embodiment, the Er concentration added to the silica-based core 3 is made uniform in the X direction, and is maximum (1 × 1020 atoms / cm 3 ) near the center of the core 3 in the Y direction. It was made to decrease in a Gaussian distribution toward the periphery of the core 3, and at the interface between the core 3 and the cladding, it became 1 × 1019 atoms Z cm 3 .
A 1， Pの濃度分布については、 A 1の場合は、 コア 3中心付近では S i 02中の S iに対して 10%の濃度を添加しており、 Pの濃度分布は、 コア 3中心付近で は S i〇2中の S iに対して 5 %にしている。 コア 3内で均一な場合は、 この濃度 で分布し、 希土類元素分布と同様な場合は、 ガウス分布となる。 A 1, for the concentration distribution of P, in the case of A 1, in the vicinity of the core 3 around which the addition of a concentration of 10% with respect to S i in S i 0 2, the concentration distribution of P, the core 3 in the vicinity of the center is 5% relative to S i in S I_〇 2. If it is uniform in the core 3, it is distributed at this concentration, and if it is similar to the rare earth element distribution, it becomes Gaussian.
A 1 , Pの濃度分布がコア内で均一な場合の光導波路の導波路利得は、 1. 6 dB/cmが得られ、 励起光強度と同様な濃度分布の場合は 2. 3 dBZcmが 得られた。  The waveguide gain of the optical waveguide is 1.6 dB / cm when the concentration distribution of A 1 and P is uniform in the core, and 2.3 dBZcm when the concentration distribution is similar to the excitation light intensity. Was done.
本実施例では、 希土類の濃度分布は、 X方向には均一、 Y方向にはガウス分布 としたが、 両方向に対してガウス分布としてもよい。  In this embodiment, the rare earth concentration distribution is uniform in the X direction and Gaussian in the Y direction, but may be Gaussian in both directions.
なお、 コア 3における希土類元素を図 7A、 図 7 Bに示す濃度分布とした光導 波路に関して、 本発明者らは、 E r濃度分布は必ずしも正確にガウス分布である 必要はないことを確認している。 図 8A、 図 8Bでは、 X方向， Y方向に対して ガウス分布からの誤差範囲となる例を示す。 図 8 Aの X方向、 図 8 Bの Y方向に 示すようにガウス分布に対して ±30%以下の誤差範囲であれば、 利得増加の効 果は悪化しないことを確認している。 図 8A, 図 8 Bにおいて、 点線はガウス分 布に対してそれぞれ + 30 %増加、 一 30 %減少した分布を示し、 実線のよう変 化する希土類元素分布であればよい。 図 8A、 図 8Bでは X， Y両方向に対して 濃度を変化するようにしたが、 どちらか一方の方向に対しては均一にしてもよい。 以下、 前述した実施例における光導波路の、 特に導波路の部分の製造方法につ いて説明する。 まず、 図 9 Aに示すように、 基板 1上に下クラッド 2を成膜し、 次いで図 9 Bに示すように、 コア 3となる膜 3 aを下クラッド 2上に形成する。 In addition, regarding the optical waveguide in which the rare earth element in the core 3 has the concentration distribution shown in FIGS.7A and 7B, the present inventors have confirmed that the Er concentration distribution does not necessarily have to be exactly Gaussian distribution. I have. 8A and 8B show examples in which the error range from the Gaussian distribution is in the X and Y directions. As shown in the X direction in Fig. 8A and the Y direction in Fig. 8B, it has been confirmed that the effect of the gain increase does not deteriorate if the error is within ± 30% of the Gaussian distribution. In FIGS. 8A and 8B, the dotted lines indicate distributions that increase by + 30% and decrease by 30%, respectively, with respect to the Gaussian distribution, and may be a rare earth element distribution that changes as indicated by the solid lines. 8A and 8B, the density is changed in both the X and Y directions. However, the density may be made uniform in one of the directions. Hereinafter, a method of manufacturing the optical waveguide in the above-described embodiment, particularly, the waveguide portion will be described. Will be described. First, as shown in FIG. 9A, a lower clad 2 is formed on a substrate 1, and then, as shown in FIG. 9B, a film 3a to be a core 3 is formed on the lower clad 2.
E) によって膜 3 aを加工し、 図 9 Cに示すように、 下クラッド 2上にコア 3が 形成された状態とする。 The film 3a is processed by E), and the core 3 is formed on the lower clad 2 as shown in FIG. 9C.
つぎに、 図 9 Dに示すように、 コア 3を覆うように上クラッド 4を形成すれば、 光導波路が完成する。 各層の成膜には、 例えば、 C V D法， スパッタリング法， 蒸着法， 火炎堆積法などを用いればよい。 上述した製造方法によれば、 コア 3内 に希土類元素や修正元素を適切な濃度分布で添加して効率のよい光増幅器を実現 している。  Next, as shown in FIG. 9D, if the upper clad 4 is formed so as to cover the core 3, the optical waveguide is completed. For the formation of each layer, for example, a CVD method, a sputtering method, an evaporation method, a flame deposition method, or the like may be used. According to the above-described manufacturing method, an efficient optical amplifier is realized by adding a rare earth element or a correction element into the core 3 with an appropriate concentration distribution.
つぎに、 コア 3内の希土類元素や修正元素を、 コア 3中心付近では高濃度にし、 コア 3の周辺に向かい減少させて添加する製造方法について説明する。 このよう に分布を持たせて希土類元素を添加するためには、 例えば、 図 1 0に示すように、 収束イオンビームにより各元素を添加すればよい。 収束イオンビームでは、 例え ば、 E r元素をイオン化してイオンビームにし、 このイオンビームをスキャンし ながらコア 3内で照射することで、 コア 3内に適当なエネルギーでイオン化した E rを注入する。 このことにより、 コア 3における E rの濃度分布が形成できる。 イオンビームとしては E r元素、 またはこの酸化物を用いればよい。 また、 修 正元素として A 1を用いる場合は、 A 1元素またはこの酸化物分子などがイオン ビームとして利用可能である。 添加濃度は、 イオン化する添加物濃度を調整する ことで制御する。 イオンビームの収束位置及び添加濃度を制御することによって、 コア 3に添加する希土類元素や修正元素の濃度 X方向分布を制御する。 さらに、 ビ一ムエネルギーを制御することによって、 添加濃度の Y方向分布も制御するこ とが可能である。  Next, a description will be given of a manufacturing method in which the rare earth element and the modifying element in the core 3 are added at a high concentration near the center of the core 3 and are reduced toward the periphery of the core 3 and added. In order to add a rare earth element with such a distribution, for example, as shown in FIG. 10, each element may be added by a focused ion beam. In a focused ion beam, for example, the Er element is ionized into an ion beam, and this ion beam is irradiated inside the core 3 while scanning, thereby implanting the ionized Er into the core 3 with an appropriate energy. . Thus, a concentration distribution of Er in the core 3 can be formed. An Er element or an oxide thereof may be used as an ion beam. When A1 is used as a modifying element, the A1 element or its oxide molecule can be used as an ion beam. The concentration of the additive is controlled by adjusting the concentration of the additive to be ionized. By controlling the convergence position of the ion beam and the addition concentration, the concentration X-direction distribution of the rare earth element or the correction element added to the core 3 is controlled. Further, by controlling the beam energy, it is possible to control the Y-direction distribution of the additive concentration.
以上に説明したことにより、 コア 3内あるいはコア 3近傍に、 濃度を Xあるい は Y方向に変化させて希土類元素や修正元素を添加した後、 コア 3を上クラッド 4で埋め込むことで、 光増幅器となる光導波路が形成できる。 上クラッド 4の成 膜には下クラッド 2やコア 3と同様の方法を用いることができる。  As described above, after changing the concentration in the X or Y direction and adding a rare earth element or a correction element in or near the core 3, the core 3 is buried in the upper cladding 4 to obtain light. An optical waveguide serving as an amplifier can be formed. The same method as for the lower cladding 2 and the core 3 can be used for forming the upper cladding 4.
また、 希土類元素や修正元素を、 前述した Y方向に変化させて添加する場合の 製造方法について、 以下に説明する。 この場合、 例えば、 図 1 1に模式的に示す スパッ夕装置によるスパッ夕法により、 コア 3を製造するようにすればよい。 例えば、 まず、 図 9 Bに示した膜 3 aを図 1 1に示すスパッ夕装置により形成 する。 このスパッ夕装置では、 S i〇2の夕一ゲッ卜と E r 2〇3のターゲットと A 1 203のターゲットとを備えたものである。 このようなスパッタ装置を用い、 各夕一 ゲットにおけるスパッ夕量を、 膜 3 aを形成している最中に変化させることによ り、 各添加物濃度を膜 3 aの膜厚方向に変化できる。 In addition, when the rare earth element and the modifying element are added while being changed in the Y direction as described above. The manufacturing method will be described below. In this case, for example, the core 3 may be manufactured by a sputter method using a sputter device schematically shown in FIG. For example, first, the film 3a shown in FIG. 9B is formed by the sputtering device shown in FIG. The sputtering in the evening apparatus is provided with a target of S I_〇 the second evening one rodents Bok and E r 2 〇 3 target and A 1 2 0 3. Using such a sputtering apparatus, the amount of each additive is changed in the thickness direction of the film 3a by changing the amount of sputter at each get while the film 3a is being formed. it can.
このようなスパッ夕装置による膜の形成は、 基板の面単位で行われるので、 X 方向 （膜面方向） には各元素濃度は均一になる。 Y方向 （膜厚方向） には、 別々 の夕ーゲットを用いているために濃度変化を、 前述した各実施例で説明したよう な濃度分布など所望の分布を実現することができる。 ここでは各元素の酸化物の ターゲットを用いたが、 酸化物でなく元素のターゲットでもよい。 また、 成膜手 法はスパッタリング法に限るものではなく、 他に C V D法， イオンプレーティン グ法， 蒸着法， 火炎堆積法などを用いることができる。 何れの場合も、 E r , A 1元素は別々の原料から供給し、 成膜するに従い供給量を変化させて所望の濃度 分布を実現することができる。  Since film formation by such a sputtering apparatus is performed in units of the surface of the substrate, the concentration of each element is uniform in the X direction (the direction of the film surface). Since different sunsets are used in the Y direction (film thickness direction), it is possible to realize a desired density change such as the density distribution described in each of the above-described embodiments. Here, an oxide target of each element is used, but an element target instead of an oxide may be used. In addition, the film forming method is not limited to the sputtering method, and other methods such as a CVD method, an ion plating method, a vapor deposition method, and a flame deposition method can be used. In any case, the elements Er and A1 can be supplied from different raw materials, and the supply amount can be changed as the film is formed to achieve a desired concentration distribution.
つぎに、 熱拡散によりコア 3における添加元素の分布を形成する製造方法につ いて説明する。  Next, a manufacturing method for forming the distribution of the additional element in the core 3 by thermal diffusion will be described.
まず、 図 1 2 Aに示すように、 基板 1上に下クラッド 2を成膜し、 次いで、 図 1 2 Bに示すように、 £ 1"ゃ£ ]： 203、 A 1や A 1 2〇3を高濃度に含んだ高濃度層 1 3 aを成膜する。 つぎに、 公知のフォトリソグラフィ技術及び R I Eなどのエツ チング技術を用い、 高濃度層 1 3 aを断面が矩形状となるように加工し、 図 1 2 Cに示すように、 下クラッド 2上にコア 3が形成された状態とする。 First, as shown in FIG. 1 2 A, forming a lower clad 2 on the substrate 1, and then, as shown in FIG. 1 2 B, £ 1 "Ya £]: 2 0 3, A 1 and A 1 A high-concentration layer 13a containing a high concentration of 成膜3 is formed Next, the high-concentration layer 13a is formed into a rectangular cross section by using a known photolithography technique and an etching technique such as RIE. The core 3 is formed on the lower clad 2 as shown in FIG. 12C.
次いで、 図 1 2 Dに示すように、 コア 3を覆うように上クラッド 4を形成する。 下クラッド 2、 高濃度層 1 3 a、 上クラッド 4は、 例えば C VD法， スパッタリ ング法， 各種蒸着法， 火炎堆積法などにより形成することができる。 この際、 上 クラッド 4の膜厚は、 コア 3が下クラッド 2と上クラッド 4からなる層のほぼ中 心にくるように調整する。  Next, as shown in FIG. 12D, an upper clad 4 is formed so as to cover the core 3. The lower cladding 2, the high concentration layer 13a, and the upper cladding 4 can be formed by, for example, a CVD method, a sputtering method, various vapor deposition methods, a flame deposition method, or the like. At this time, the thickness of the upper cladding 4 is adjusted so that the core 3 is substantially at the center of the layer composed of the lower cladding 2 and the upper cladding 4.
次いで、 図 1 2 Eに示すように、 高温ァニール処理を施してコア 3内の添加物 を周辺へ拡散させる。 これにより、 図 1 2 Dの時点でコア 3に均一に添加されて いた希土類元素や修正元素濃度は、 コア 3中心部近傍で高く、 コア 3の周辺に向 かって X方向及び Y方向に徐々に減少する構造となる。 Next, as shown in FIG. 12E, a high-temperature annealing treatment is performed to To the surroundings. As a result, the concentration of the rare earth element and the modifying element uniformly added to the core 3 at the time of FIG. 12D is high near the center of the core 3 and gradually increases in the X and Y directions toward the periphery of the core 3. The structure is reduced.
ところで、 上述では、 高濃度層 1 3 aを加工してコア 3を形成したが、 これに 限るものではない。 例えば、 つぎに示すようにしてコアを形成してもよい。 まず、 図 1 2 Fに示すように、 基板 1上に下クラッド 2 aを形成する。 下クラッド 2 a は、 例えば、 図 1 2 Bに示す下クラッド 2と高濃度層 1 3 aとの膜厚を合計した 膜厚に形成する。 次いで、 公知のフォトリソグラフィ技術及び R I Eなどのエツ チング技術を用い、 図 1 2 Gに示すように、 下クラッド 2 aに溝を形成する。 つぎに、 下クラッド 2 aに形成した溝が埋まるように、 下クラッド 2 a上に E rや E r 2〇3、 A 1や A 1 203を高濃度に添加した膜を形成する。 溝がこの膜で埋め 込まれるようにするために、 例えば、 熱によるリフローなどを用いてもよい。 次 いで溝部以外の余分な部分をエッチバックまたは研磨によって除去し、 図 1 2 H に示すように、 下クラッド 2 aの溝内にコア 3が形成された状態とする。 By the way, in the above, the core 3 was formed by processing the high concentration layer 13a, but the present invention is not limited to this. For example, the core may be formed as follows. First, as shown in FIG. 12F, a lower cladding 2 a is formed on a substrate 1. The lower cladding 2a is formed, for example, to have a total thickness of the lower cladding 2 and the high concentration layer 13a shown in FIG. 12B. Next, a groove is formed in the lower clad 2a as shown in FIG. 12G by using a known photolithography technique and an etching technique such as RIE. Next, as filled grooves formed in the lower clad 2 a, to form a film added with E r and E r 2 〇 3, A 1 and A 1 2 0 3 at a high concentration on the lower clad 2 a. In order to fill the groove with this film, for example, reflow by heat or the like may be used. Next, excess portions other than the groove portions are removed by etch-back or polishing, so that the core 3 is formed in the grooves of the lower cladding 2a as shown in FIG. 12H.
つぎに、 図 1 2 1に示すように、 コア 3を覆うように上クラッド 4 aを形成す る。 下クラッド 2 a、 上記膜、 上クラッド 4 aは、 例えば C V D法， スパッ夕リ ング法， 各種蒸着法， 火炎堆積法などにより形成することができる。 この際、 上 クラッド 4 aの膜厚は、 コア 3が下クラッド 2 aと上クラッド 4 aからなる層の ほぼ中心にくるように調整する。  Next, as shown in FIG. 121, an upper clad 4 a is formed so as to cover the core 3. The lower cladding 2a, the above-mentioned film, and the upper cladding 4a can be formed by, for example, a CVD method, a sputtering method, various vapor deposition methods, a flame deposition method, or the like. At this time, the thickness of the upper cladding 4a is adjusted such that the core 3 is substantially at the center of the layer composed of the lower cladding 2a and the upper cladding 4a.
最後に、 図 1 2 Jに示すように、 高温ァニール処理を施してコア 3内の添加物 を周辺へ拡散させる。 これにより、 図 1 2 Iの時点でコア 3に均一に添加されて いた希土類元素や修正元素濃度は、 コア 3中心部近傍で高く、 コア 3の周辺に向 かって X方向及び Y方向に徐々に減少する構造となる。  Finally, as shown in FIG. 12J, a high-temperature annealing treatment is performed to diffuse the additives in the core 3 to the periphery. As a result, the concentration of the rare earth element and the correction element uniformly added to the core 3 at the time of Fig. 12I is high near the center of the core 3 and gradually increases in the X and Y directions toward the periphery of the core 3. The structure is reduced.
なお、 上述では、 上クラッド 4 (上クラッド 4 a ) を形成した後に、 E rや A 1の拡散のための高温熱処理を施したが、 コア 3の周りを囲む低濃度の層を形成 した後、 高温熱処理して E rや A 1を拡散してから上クラッドを形成するように してもよい。  In the above description, after forming the upper cladding 4 (upper cladding 4 a), a high-temperature heat treatment for diffusion of Er and A 1 was performed, but after forming a low-concentration layer surrounding the core 3. Alternatively, the upper clad may be formed after heat treatment at a high temperature to diffuse Er and A1.
上述した製造方法により、 例えば、 E rを 3 X 1 0 2 0原子 Z c m3， 八 1を1 O w t %、 Pを 1 2 w t %添加した S i〇2からなる高濃度層 1 3 aを形成し、 こ れを加工して断面寸法が 0 . 8 X 0 . 8 mのコア 3を形成し、 上クラッド 4を 形成した後で、 酸素雰囲気中で 1 0 0 0 のァニール処理を 3時間行うことで、 図 1 B、 図 1 Cに示した濃度分布のコアを備えた光導波路を得ることができる。 上述した実施例によれば、 コアにおける希土類元素に周辺に行くほど濃度が低 くなるような濃度分布を持たせるようにしたので、 主に、 コアの中心部で光信号 が増幅されるようになる。 この結果、 本発明によれば、 導波路型の光増幅器にお いてより高い利得が得られるようになるという優れた効果が得られる。 According to the above-described manufacturing method, for example, a high-concentration layer 13 a made of 3 × 10 20 atoms Z cm 3 , Si 1 added with 1 O wt% of 81 and 12 wt% of P, and To form This was processed to form a core 3 with a cross-sectional dimension of 0.8 x 0.8 m, and after forming the upper cladding 4, an annealing process of 100 in oxygen atmosphere was performed for 3 hours. An optical waveguide having the core having the concentration distribution shown in FIGS. 1B and 1C can be obtained. According to the above-described embodiment, the rare earth element in the core is provided with a concentration distribution such that the concentration decreases toward the periphery, so that the optical signal is mainly amplified at the center of the core. Become. As a result, according to the present invention, an excellent effect that higher gain can be obtained in the waveguide type optical amplifier can be obtained.
以上のように、 本発明にかかる平面型導波路を用いた光導波路は、 長距離の波 長多重通信に用いるのに適している。  As described above, the optical waveguide using the planar waveguide according to the present invention is suitable for use in long-distance wavelength multiplex communication.

Claims

請 求 の 範 囲 The scope of the claims
1 . 基板と、 基板上に形成されたクラッドと、 クラッド中に配置されたコアと、 から構成された光導波路であって、 1. An optical waveguide comprising: a substrate; a clad formed on the substrate; and a core disposed in the clad,
前記コアには、  In the core,
所定の濃度分布を備えた希土類元素と、  A rare earth element having a predetermined concentration distribution;
前記希土類元素のクラスタ一化を抑制する機能、 および前記希土類元素を励起 光で励起して信号光の増幅帯域を広げる機能のうち少なくとも一方を備えた修正 元素とが添加されていることを特徴とする光導波路。  A correcting element having at least one of a function of suppressing clustering of the rare earth elements and a function of exciting the rare earth elements with excitation light to broaden an amplification band of signal light, is added. Optical waveguide.
2 . 前記希土類元素は、  2. The rare earth element is
中心部より周辺部にかけて徐々に濃度が減少する濃度分布を備えたことを特徴 とする請求項 1に記載の光導波路。  2. The optical waveguide according to claim 1, wherein the optical waveguide has a concentration distribution in which the concentration gradually decreases from a central portion to a peripheral portion.
3 . 前記希土類元素は、  3. The rare earth element is
前記基板平面方向には中心部より周辺部にかけて濃度が均一であり、 前記基板 平面に垂直な方向には中心部より周辺部にかけて徐々に濃度が減少する濃度分布 を備えたことを特徴とする請求項 1に記載の光導波路。  Wherein the substrate has a concentration distribution in which the concentration is uniform from the center to the periphery in the plane direction of the substrate, and the concentration gradually decreases from the center to the periphery in the direction perpendicular to the substrate plane. Item 2. An optical waveguide according to item 1.
4. 前記修正元素は、 前記コア内に均一に添加されていることを特徴とする請 求項 1に記載の光導波路。  4. The optical waveguide according to claim 1, wherein the modifying element is uniformly added in the core.
5 . 前記修正元素は、 前記コア内の前記希土類元素の濃度分布と同様の分布で 前記コア内に添加されていることを特徴とする請求項 1に記載の光導波路。  5. The optical waveguide according to claim 1, wherein the modifying element is added to the core in a distribution similar to the concentration distribution of the rare earth element in the core.
6 . 前記希土類元素の濃度分布は、  6. The concentration distribution of the rare earth element is
前記コアを伝搬する光の強度分布と同様の分布、  A distribution similar to the intensity distribution of light propagating through the core,
前記コアの中心部で最大となり周辺部に行くほど小さくなるガウス分布、 前記コアの中心部で最大となり周辺部に行くほど小さくなるガウス分布からの 偏差の割合が土 3 0 %以内の分布  The distribution of the deviation from the Gaussian distribution which is maximum at the center of the core and becomes smaller toward the periphery and becomes smaller toward the periphery of the core within 30% of soil.
の何れかの分布の範囲である  Range of any distribution of
ことを特徴とする請求項 1に記載の光導波路。  The optical waveguide according to claim 1, wherein:
7 . 前記修正元素は、 A l， B , G a , I n , G e , S n， B i , N, P， Y bの少なくとも何れか 1つであることを特徴とする請求項 1に記載の光導波路。7. The correction elements are Al, B, Ga, In, Ge, Sn, Bi, N, P, Y. 2. The optical waveguide according to claim 1, wherein the optical waveguide is at least one of b.
8 . 前記希土類元素は、 8. The rare earth element is
E r , Tm, P r , N dの少なくとも何れか 1つであることを特徴とする請求 項 1に記載の光導波路。  2. The optical waveguide according to claim 1, wherein the optical waveguide is at least one of Er, Tm, Pr, and Nd.
9 . 前記コアの主な成分は、 酸化シリコン， 酸化アルミニウム， 酸化ビスマス の少なくとも何れか 1つを含むことを特徴とする請求項 1に記載の光導波路。 9. The optical waveguide according to claim 1, wherein a main component of the core includes at least one of silicon oxide, aluminum oxide, and bismuth oxide.
1 0 . 基板上に下クラッドを形成する工程と、 10. Forming a lower cladding on the substrate;
前記下クラッド上に、 中心部に高濃度に希土類元素及び修正元素が含まれたコ ァを形成する工程と、  Forming a core containing a rare earth element and a modifying element at a high concentration in a central portion on the lower clad;
前記下クラッド及び前記コア上に上クラッドを形成する工程と  Forming an upper cladding on the lower cladding and the core;
を備え、  With
前記修正元素は、 前記コァに添加された希土類元素のクラス夕一化を抑制する 機能、 および前記コアに添加された希土類元素を励起光で励起して信号光の増幅 帯域を広げる機能の少なくとも一方を備えた元素からなることを特徴とする光導 波路の製造方法。  The modifying element has at least one of a function of suppressing class disintegration of the rare earth element added to the core and a function of exciting the rare earth element added to the core with excitation light to broaden an amplification band of signal light. A method for producing an optical waveguide, comprising: an element having:
1 1 . 前記コアを形成する工程は、  1 1. The step of forming the core comprises:
前記下クラッド上にコアとなる膜を形成する工程と、  Forming a film serving as a core on the lower clad,
前記膜に、 収束イオンビ一ムを走査しながら希土類元素及び修正元素を注入し、 この希土類元素及び前記修正元素が前記コアの中心部より周辺部にかけて徐々に 濃度が減少する濃度分布を備えた状態とする工程と  A rare earth element and a correction element are implanted into the film while scanning the focused ion beam, and the rare earth element and the correction element have a concentration distribution in which the concentration gradually decreases from the center to the periphery of the core. And the process
を備えることを特徴とする請求項 1 0に記載の光導波路の製造方法。 10. The method for manufacturing an optical waveguide according to claim 10, comprising:
1 2 . 前記コアを形成する工程は、  1 2. The step of forming the core includes:
前記下クラッド上に、 コアの主たる成分を含む第 1のターゲットと、 希土類元 素を含む第 2のターゲットと、 修正元素を含む第 3のターゲットとを用いた成膜 方法により、 希土類元素の濃度が膜の中央部より上下の周辺部にかけて徐々に減 少し、 前記修正元素の濃度が前記膜の内部で一定の状態および中央部より上下の 周辺部にかけて徐々に減少する状態の何れかとなる濃度分布を備えるように形成 する工程を備えることを特徴とする請求項 1 0に記載の光導波路の製造方法。 On the lower clad, the concentration of the rare earth element is determined by a film forming method using a first target containing a main component of the core, a second target containing a rare earth element, and a third target containing a correction element. Concentration gradually decreases from the center to the upper and lower peripheral portions of the film, and the concentration of the correction element becomes one of a constant state inside the film and a state of gradually decreasing from the center to the upper and lower peripheral portions. 10. The method of manufacturing an optical waveguide according to claim 10, further comprising a step of forming the optical waveguide.
1 3 . 前記コアを形成する工程は、 前記第 2の夕一ゲット及び第 3の夕一ゲットのスパッタ状態を変化させるスパ ッ夕リング法により形成する工程を備えることを特徴とする請求項 1 2に記載の 光導波路の製造方法。 1 3. The step of forming the core includes: 13. The method of manufacturing an optical waveguide according to claim 12, further comprising a step of forming the second evening get and the third evening get by a sputtering method for changing a sputter state.
1 4 . 前記コアを形成する工程は、  1 4. The step of forming the core includes:
前記第 2のターゲット及び前記第 3のターゲットの蒸発状態を変化させるィォ ンプレーティング法により形成する工程を備えることを特徴とする請求項 1 2に 記載の光導波路の製造方法。  13. The method of manufacturing an optical waveguide according to claim 12, further comprising a step of forming the second target and the third target by an ion plating method that changes an evaporation state of the third target.
1 5 . 前記コアを形成する工程は、  1 5. The step of forming the core includes:
前記第 2の夕一ゲットの蒸発量を変化させる蒸着法により形成する工程を備え ることを特徴とする請求項 1 2に記載の光導波路の製造方法。  13. The method of manufacturing an optical waveguide according to claim 12, further comprising a step of forming the second evening get by an evaporation method that changes an amount of evaporation.
1 6 . 前記第 2のターゲットと前記第 3のターゲットは、 希土類元素と前記修 正元素とを同時に含む同一のターゲッ卜から構成されたものであることを特徴と する請求項 1 2に記載の光導波路の製造方法。  16. The method according to claim 12, wherein the second target and the third target are composed of the same target containing a rare earth element and the modifying element at the same time. Manufacturing method of optical waveguide.
1 7 . 前記コアを形成する工程は、  1 7. The step of forming the core includes:
前記下クラッド上に、 コアの主たる成分を含む第 1のソースガスと、 希土類元 素を含む第 2のソースガスと、 修正元素を含む第 3のソースガスとを導入する化 学的気相成長法により、 希土類元素の濃度が膜の中央部より上下の周辺部にかけ て徐々に減少し、 前記修正元素の濃度が前記膜の内部で一定の状態および中央部 より上下の周辺部にかけて徐々に減少する状態の何れかとなる濃度分布を備える ように形成する工程を備えることを特徴とする請求項 1 0に記載の光導波路の製 造方法。  Chemical vapor deposition in which a first source gas containing a main component of a core, a second source gas containing a rare earth element, and a third source gas containing a correction element are introduced onto the lower clad. By the method, the concentration of the rare earth element gradually decreases from the central part of the film to the upper and lower peripheral parts, and the concentration of the correction element gradually decreases in a constant state inside the film and the upper and lower peripheral parts from the central part. 10. The method for manufacturing an optical waveguide according to claim 10, further comprising a step of forming the optical waveguide so as to have a concentration distribution in any of the following states.
1 8 . 前記コアを加熱して前記希土類元素及び前記修正元素を拡散させること により、 前記希土類元素及び修正元素が前記コアの中心部より周辺部にかけて徐 々に濃度が減少する濃度分布を備えた状態とする工程を  18. By heating the core to diffuse the rare earth element and the modifying element, the core has a concentration distribution in which the concentration of the rare earth element and the modifying element gradually decreases from the central portion to the peripheral portion of the core. State
さらに備えることを特徴とする請求項 1 0に記載の光導波路の製造方法。 The method for manufacturing an optical waveguide according to claim 10, further comprising:
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