CN103676219B - Low polarization dependent loss lithium niobate straight-bar waveguide phase modulator and manufacturing method thereof - Google Patents
Low polarization dependent loss lithium niobate straight-bar waveguide phase modulator and manufacturing method thereof Download PDFInfo
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- CN103676219B CN103676219B CN201310714376.4A CN201310714376A CN103676219B CN 103676219 B CN103676219 B CN 103676219B CN 201310714376 A CN201310714376 A CN 201310714376A CN 103676219 B CN103676219 B CN 103676219B
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Abstract
The invention relates to a low polarization dependent loss lithium niobate straight-bar waveguide phase modulator and a manufacturing method of the low polarization dependent loss lithium niobate straight-bar waveguide phase modulator. The low polarization dependent loss lithium niobate straight-bar waveguide phase modulator comprises a lithium niobate optical waveguide chip, a first polarization-maintaining pigtail assembly and a second polarization-maintaining pigtail assembly, wherein the first polarization-maintaining pigtail assembly and the second polarization-maintaining pigtail assembly are bonded to the two ends of the lithium niobate optical waveguide chip in a coupling mode respectively, the lithium niobate optical waveguide chip comprises a lithium niobate substrate, a titanium diffusion waveguide area, annealing external diffusion areas and metal electrodes, an x-cut y-pass chip is adopted for the lithium niobate substrate, the titanium diffusion waveguide area and the annealing external diffusion areas are arranged on the surface layer of the lithium niobate substrate, the annealing external diffusion areas are arranged on the two sides of the titanium diffusion waveguide area respectively, the metal electrodes are arranged on the surfaces of the annealing external diffusion areas, the positive electrode and the negative electrode are symmetrical about the titanium diffusion waveguide area, and the first polarization-maintaining pigtail assembly and the second polarization-maintaining pigtail assembly respectively comprise a first polarization-maintaining optical fiber and a first optical fiber fixing block. The low polarization dependent loss lithium niobate straight-bar waveguide phase modulator achieves low insertion loss and low polarization dependent loss of a device at the same time, and achieves power even distribution of two polarization states, the situation of modulation waveform distortion is effectively eliminated, and accuracy of electro-optical modulation is improved.
Description
Technical field
The present invention relates to a kind of preparation method of lithium niobate base integrated optical device, more particularly to low Polarization Dependent Loss
Lithium metaniobate vertical bar Waveguide Phase Modulator and preparation method thereof.
Background technology
Low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator being capable of simultaneous transmission te and tm mould can be simultaneously right
The phase place of this two patterns is modulated, and this characteristic makes it in the development of sensory field of optic fibre particularly fibre optic current sensor
In enjoy favor.Using this device, the simply conllinear type fibre optic current sensor light path of one kind can be formed.With its other party light path
Scheme such as sagnac light path scheme is compared, and the light path of the program has less temperature error and linearly coupled error, there is not angle
Vibration error, and time reciprocity is best.Thus the manipulator using low Polarization Dependent Loss Lithium metaniobate vertical bar waveguide phase place
Current sensor light channel structure can be made to reduce the nonreciprocal error of light path system to greatest extent, be conducive to improving fibre-optic current
The precision of sensor.
In the application such as fibre optic current sensor, the basic demand that device is proposed is: insertion loss is low and to two
It is low, furthermore it is required that two polarize that polarization mode has the Polarization Dependent Loss (pdl) that efficiency of transmission as equal as possible is device
Between mould, polarization crosstalk is low, and is ensured that its temperature stability in engineer applied.
At present in waveguide modulator, the waveguide of lithium niobate base occupies electricity due to the excellent optics of its substrate and electro-optical properties
The leading position of photomodulator.The preparation of lithium niobate base waveguide modulator has two schemes, and one kind is titanium diffusion technique, another kind of
It is particle exchanging technology.Wherein particle exchanging technology increases its extraordinary ray refractive index ne, and reduce its ordinary anaclasis simultaneously
Rate no, thus the waveguide being formed can only carry the pattern of extraordinary polarization state.And titanium diffusion technique can increase Lithium metaniobate simultaneously
Extraordinary ray refractive index n of crystaleWith ordinary refraction index no, only therefore to realize the lithium niobate waveguides of low Polarization Dependent Loss
Titanium diffusion technique can be adopted.
Titanium diffusion technique on Lithium metaniobate, has more reported in literature at present, but is all merely with it in these documents
One polarization mode (te or tm mould), and another mould is sponged and ultimately forms single device polarizing work, therefore set in device
The pattern intending sponging can not considered in meter and chip preparation.When two polarization modes of device are all mode of operations
When, the design of device and processing must take into account the transmission characteristic of two patterns simultaneously.However, due to corresponding to two polarization modes
Refractive index different, and also differed greatly by the index increment that titanium diffusion causes, therefore will take into account two patterns simultaneously
Transmission characteristic just increases the preparation difficulty of device.
Content of the invention
It is an object of the invention to overcoming the above-mentioned deficiency of prior art, provide low Polarization Dependent Loss Lithium metaniobate vertical bar ripple
Lead phase-modulator, this vertical bar Waveguide Phase Modulator realizes device low insertion loss and low Polarization Dependent Loss simultaneously, realize
The power-sharing of two polarization states, can effectively eliminate the situation of modulation waveform distortion, improve Electro-optical Modulation precision.
Another object of the present invention is to provide low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator
Preparation method.
The above-mentioned purpose of the present invention is mainly achieved by following technical solution:
Low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, couples including lithium niobate fiber waveguide chip and respectively
It is bonded in the first inclined pigtail assembly of guarantor and the second inclined pigtail assembly of guarantor at lithium niobate fiber waveguide chip two ends, the first inclined tail optical fiber group of guarantor
Part is input, and second protects inclined pigtail assembly for outfan, and wherein lithium niobate fiber waveguide chip includes lithium niobate substrate, titanium diffusion
Waveguide section, annealing regions of out-diffusion and metal electrode, lithium niobate substrate is cut y using x and is passed chip, titanium diffusion zone and annealing external diffusion
Area is located at the top layer of lithium niobate substrate, and regions of out-diffusion of annealing is located at the both sides of titanium diffusion zone, and it is outer that metal electrode is located at annealing
The surface of diffusion region, and positive and negative electrode is symmetrical with regard to titanium diffusion zone；First guarantor inclined pigtail assembly include the first polarization maintaining optical fibre and
First optical fiber fixed block, the first polarization maintaining optical fibre is bonded in the first V-shaped groove of the first optical fiber fixed block surface, the second inclined tail optical fiber of guarantor
Assembly includes the second polarization maintaining optical fibre and the second optical fiber fixed block, and the second polarization maintaining optical fibre is bonded in the of the second optical fiber fixed block surface
In two V-shaped grooves.
In above-mentioned low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, the slow axis of the first polarization maintaining optical fibre and
The axis of symmetry angle of one V-shaped slot cross-section is 45 °；The slow axis of the second polarization maintaining optical fibre with the axis of symmetry angle of the second V-shaped slot cross-section is
0°.
In above-mentioned low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, the first optical fiber fixed block and the second light
Fine fixed block is rectangular blocks, and material is silicon crystal, and the first V-shaped groove on surface or the second V-shaped groove are formed by wet etching.
In above-mentioned low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, the width of titanium diffusion zone is 4～8
Micron, thickness is 2～6 microns.
In above-mentioned low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, the thickness of annealing regions of out-diffusion is 2
～6 microns.
In above-mentioned low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, in metal electrode between positive and negative electrode
Distance be 10～20 microns.
The preparation method of low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, including lithium niobate fiber waveguide chip
Preparation process and first protect inclined pigtail assembly, the second bonding process protecting inclined pigtail assembly and lithium niobate fiber waveguide chip,
The preparation process of wherein lithium niobate fiber waveguide chip is as follows:
The first step, chooses x and cuts y biography lithium niobate crystal chip, by lithography stripping technique or wet etching photoetching process, in conjunction with titanium
The growth of film, forms the straight wave guide figure of titanium film in wafer surface；
Second step, the chip after the first step is processed is put into and is carried out titanium diffusion in diffusion furnace, and the titanium being formed on Lithium metaniobate expands
Scattered waveguide section；
3rd step, the chip after second step is processed carries out, in non-titanium diffused waveguide region, external diffusion process of annealing, and is formed
Annealing regions of out-diffusion；
4th step, prepares metal electrode on annealing regions of out-diffusion surface, and makes metal electrode symmetrical with regard to titanium diffusion zone,
Prepare lithium niobate fiber waveguide chip；
Wherein first protects the bonding process of inclined pigtail assembly, the second inclined pigtail assembly of guarantor and lithium niobate fiber waveguide chip such as
Under:
5th step, two second is protected inclined pigtail assembly difference clamping on two sextuple micropositioning stages, the 4th step is prepared into
To lithium niobate fiber waveguide chip clamping on a slide holder；
6th step, by one of them second protect inclined pigtail assembly in second polarization maintaining optical fibre 6a access polarization tunable optical
Source, the second polarization maintaining optical fibre 6b that another one second is protected in inclined pigtail assembly accesses light power meter；
7th step, sextuple micropositioning stage other five dimensions in addition to rotating along optical fiber axial direction of regulation two, make described two second
Polarization maintaining optical fibre 6a, 6b are aligned with titanium diffused waveguide area；
8th step, the second polarization maintaining optical fibre 6b is accessed after light power meter takes off extinction ratio tester, finely tune two simultaneously
The axial-rotation of second polarization maintaining optical fibre 6a, 6b, often finely tunes an axial-rotation, reads primary extinction than data, reads extinction ratio
The method of data is: the polarization state of rotatory polarization tunable optical source one week, omits the symbol before extinction ratio tester registration, sees
Four maximum occurring successively are examined on extinction ratio tester, described four maximum are as the absolute value of extinction ratio measurement value；
9th step, repetition the 8th step, the absolute value of four extinction ratio data until recording reaches maximum；
Tenth step, keep second polarization maintaining optical fibre 6a, 6b axial-rotation motionless, by the second polarization maintaining optical fibre 6b from extinction ratio survey
Examination instrument takes off and is followed by optical power meter, adjusts other five dimensions of second polarization maintaining optical fibre 6a, 6b, until the luminous power that detects
Greatly；
11st step, the second polarization maintaining optical fibre 6b end face point ultraviolet glue, and adjust again the second polarization maintaining optical fibre 6b remove axle
Other five dimensions to outside rotation, until the maximum optical power detecting；
12nd step, ultraviolet glue is exposed solidify, completes Lithium metaniobate light wave on the second polarization maintaining optical fibre 6b and slide holder
Lead being of coupled connections of chip one end；
13rd step, the second polarization maintaining optical fibre 6a is taken off from sextuple micropositioning stage, the first polarization maintaining optical fibre assembly is contained in institute
State on sextuple micropositioning stage；
14th step, by the first polarization maintaining optical fibre assembly first polarization maintaining optical fibre access low polarization wide spectrum light source, by second
Polarization maintaining optical fibre 6b accesses light power meter；
15th step, regulation the first polarization maintaining optical fibre other five dimensions in addition to axial-rotation, make the first polarization maintaining optical fibre expand with titanium
Scattered regional alignment；
16th step, the second polarization maintaining optical fibre 6b is entered after light power meter takes off extinction ratio tester, fine setting is equipped with first
The sextuple micropositioning stage of polarization maintaining optical fibre assembly, until the power that extinction ratio tester is measured is maximum, extinction ratio is minimum；
17th step, the first polarization maintaining optical fibre end face point ultraviolet glue, ultraviolet glue is exposed solidify, complete the first guarantor
Polarisation fine with being of coupled connections of the lithium niobate fiber waveguide chip other end on slide holder.
In the preparation method of above-mentioned low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator, the 3rd step is to chip
Carry out, in non-titanium diffused waveguide region, external diffusion process of annealing, form specifically comprising the following steps that of annealing regions of out-diffusion
(1) chip after, processing second step is carried out, and forms the titanium diffusion with formation in the first step in wafer surface
The silicon dioxide pattern that region is completely superposed, that is, silicon dioxide titanium diffused waveguide region is completely covered；
(2), place a wafer in annealing furnace, annealed under conditions of logical oxygen, form annealing regions of out-diffusion.
Compared with the prior art, the invention has the advantages that:
(1) in the present invention, lithium niobate fiber waveguide chip introduces an annealing regions of out-diffusion outside titanium diffused waveguide area, permissible
Maximum possible reduces the difference between two mode refractive index increments of waveguide, realize the te mould of waveguide and tm mould have roughly equal
Spot size, two patterns have the coupling efficiency roughly equal with optical fiber, thus device has that less polarization is related to be damaged
Consumption (pdl)；
(2) slow axis of the first inclined tail optical fiber 5 of guarantor and the Lithium metaniobate of the input of manipulator of preparation method preparation of the present invention are adopted
The crystallographic axis of crystal becomes about 45 ° of be aligneds, ensure that minimum Polarization Dependent Loss realized by whole device, realizes two polarization modes
Power-sharing；
(3) structure on lithium columbate crystal surface is directly prepared using modulation metal electrode, modulating wave can be effectively reduced
The distortion of shape, improves Electro-optical Modulation efficiency and modulation accuracy.
(4), in lithium niobate fiber waveguide chip preparation method of the present invention, carry out annealing after titanium diffusion technique terminates again and extend out
Scattered technical process, due to annealing external diffusion process compare titanium diffusion process temperature much lower, therefore anneal external diffusion technique
Do not interfere with the index distribution of titanium diffusion region；Additionally, titanium diffusion technique and annealing external diffusion technique are the work of relative maturity
Skill, and external diffusion technique of annealing only changes extraordinary ray refractive index, therefore device chip are realized process and are relatively easy to；
(5) Lithium metaniobate vertical bar waveguide of the present invention devises annealing regions of out-diffusion outside titanium diffused waveguide area, so designs
Device chip can realize device low insertion loss and low Polarization Dependent Loss simultaneously；Butt coupling in its optical fiber and waveguide chip
In mode, especially specify that the corresponding relation between optical fiber axial direction and crystal crystal orientation, optical fiber axial direction and optical fiber fixed block, Jin Erneng
Enough Polarization Dependent Loss reducing device further, realize the power-sharing of two polarization states.By modulator electrode is directly made
The standby situation that can effectively eliminate modulation waveform distortion on lithium columbate crystal, improves Electro-optical Modulation precision；
(6) present invention, in the preparation process of Lithium metaniobate vertical bar waveguide, is carried out to the butt coupling method of optical fiber and chip
Innovative design, especially achieves optical fiber axial direction with being aligned of crystal crystal orientation it is achieved that dividing equally of two polarization state power.
Brief description
Fig. 1 is lithium niobate fiber waveguide chip structure schematic diagram in the present invention.
Fig. 2 be the present invention low Polarization Dependent Loss Lithium metaniobate straight waveguide phase modulator chip cross-sectional view (x cuts
Y passes crystal).
Fig. 3 is the structural representation of the optical fiber fixed block in the present invention with V-shaped groove.
Fig. 4 is first, second polarization maintaining optical fibre modular construction schematic diagram in the present invention, and wherein 4a is the first polarization maintaining optical fibre group
Part, 4b is the second polarization maintaining optical fibre assembly.
Fig. 5 is directed to the view after the optical fiber and fixed block polishing of lithium columbate crystal chip for the present invention；
Fig. 6 is directed to the view after the optical fiber and fixed block polishing of lithium columbate crystal chip for the present invention.
Specific embodiment
The present invention is described in further detail with specific embodiment below in conjunction with the accompanying drawings:
The present invention low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator includes lithium niobate fiber waveguide chip and divides
It is not coupling in the first inclined pigtail assembly of guarantor and the second inclined pigtail assembly of guarantor at lithium niobate fiber waveguide chip two ends, wherein first protects partially
Pigtail assembly and second protects one end that inclined pigtail assembly is respectively bonded in lithium niobate fiber waveguide chip, and the first inclined pigtail assembly of guarantor is
Input, second protects inclined pigtail assembly for outfan.Lithium niobate fiber waveguide chip and first is protected inclined pigtail assembly and second and is protected partially
Pigtail assembly is encapsulated in shell, and first protects the first polarization maintaining optical fibre (5) and the second inclined pigtail assembly of guarantor in inclined pigtail assembly
In the second polarization maintaining optical fibre (6) stretch out outside shell, be easy to the connection with other optical fibre devices.
It is illustrated in figure 1 lithium niobate fiber waveguide chip structure schematic diagram in the present invention, Fig. 2 show the present invention low polarization phase
Close the chip cross-sectional view (x cuts y and passes crystal) of loss Lithium metaniobate straight waveguide phase modulator, Lithium metaniobate light wave as shown in the figure
Lead chip and include lithium niobate substrate 1, titanium diffused waveguide area 2, annealing regions of out-diffusion 3 and metal electrode 4, lithium niobate substrate 1 adopts x
Cut y and pass chip, titanium diffusion zone 2 and annealing regions of out-diffusion 3 are positioned at the top layer of lithium niobate substrate 1, and regions of out-diffusion 3 of annealing is located at
The both sides of titanium diffusion zone 2, metal electrode 4 is located at the surface of annealing regions of out-diffusion 3, and both positive and negative polarity is located at titanium diffused waveguide area 2
Both sides, position is symmetrical with regard to titanium diffusion zone 2.The width of wherein titanium diffusion zone 2 is 4～8 microns, and thickness is 2～6 microns；
The thickness of annealing regions of out-diffusion 3 is 2～6 microns；In metal electrode 4, the gap of positive and negative electrode is 10～20 microns.
It is illustrated in figure 3 the structural representation of the optical fiber fixed block carrying V-shaped groove in the present invention, Fig. 4 show the present invention
In first, second polarization maintaining optical fibre modular construction schematic diagram, wherein 4a be the first polarization maintaining optical fibre assembly, 4b be the second polarization maintaining optical fibre group
Part, as seen from the figure the first inclined pigtail assembly of guarantor include the first polarization maintaining optical fibre 5 and the first optical fiber fixed block 7, the first polarization maintaining optical fibre 5 glues
It is connected in the first V-shaped groove 8 on the first optical fiber fixed block 7 surface, the second inclined pigtail assembly of guarantor includes the second polarization maintaining optical fibre 6 and second
Optical fiber fixed block 7 ', the second polarization maintaining optical fibre 6 is bonded in the second V-shaped groove 8 ' on the second optical fiber fixed block 7 ' surface.As Fig. 4 a institute
Show that the slow axis of the first polarization maintaining optical fibre 5 and the axis of symmetry angle in the first V-shaped groove 8 section are 45 °；Second polarization maintaining optical fibre as shown in Figure 4 b
The axis of symmetry angle in 6 slow axis and the second V-shaped groove 8 ' section is 0 °, and the z of the slow axis of the second polarization maintaining optical fibre 6 and lithium columbate crystal
Axle is mutually perpendicular to.
First optical fiber fixed block 7 and the second optical fiber fixed block 7 ' are rectangular blocks, and material is silicon crystal, and the of surface
One V-shaped groove 8 and the second V-shaped groove 8 ' are formed by wet etching.
The principle of the present invention is as follows:
Coupling loss between the waveguide of waveguide device and optical fiber is the important composition part of waveguide device loss, only drops
Lower coupling loss just can ensure that device has low insertion loss.When the mode spot-size of waveguide and the mode spot-size of tail optical fiber are consistent
When, waveguide has minimum coupling loss, therefore, adjusts waveguiding structure parameter and technological parameter, makes waveguide mode spot-size close
In optical fiber mode spot-size be the preparation of device design and processes one of target.
In the waveguide preparation technology of Lithium metaniobate, titanium diffusion technique can change the extraordinary ray folding of lithium columbate crystal simultaneously
Penetrate rate neWith ordinary refraction index no, but in conventional 1.31um and 1.55um wave band, its extraordinary ray index increment δ neAll
Refractive index δ n more than ordinary lighto, this species diversity typically all can meet or exceed 2 times.Therefore for two polarization modes,
The normalization thickness of its waveguide has very big difference, necessarily causes noCorresponding polarization mode ends close to single mode, neCorresponding inclined
The mould that shakes is even up to multimode area away from single mode cut-off, and the former spot size can be much larger than the latter.When one of close to light
During fine hot spot, the hot spot of another polarization mode then can be away from hot spot, thus the overall losses of impact and pdl.Although can be to drop
The pdl of low device is target, and adjustment diffusion parameter makes the hot spot one of two polarization modes be more than optical fiber facula, and one is less than optical fiber
Hot spot and make two polarization modes have approximately equalised coupling efficiency to optical fiber, thus reducing pdl, it will be apparent that device insert
Entering loss is not minimum state.Additionally, n in this stateeCorresponding polarization mode often comes into multimode area, device
The temperature stability of part performance can substantially reduce.Therefore, only low insertion loss, low pdl and property are realized by titanium diffusion technique
The temperature stability of energy is highly difficult.
Annealing out diffusion technique provides approach with the above-mentioned situation of change that is combined into of titanium diffusion technique.Annealing external diffusion skill
The feature of art is: anneals under the high temperature conditions, realizes li2The external diffusion of o, this increases extraordinary ray refractive index n of Lithium metaniobatee
And its ordinary refraction index noConstant.If annealing external diffusion process is confined to non-titanium diffused waveguide region, titanium is spread
For waveguide region, the index increment of its extraordinary ray opposed peripheral regions is reduced, and the index increment phase of ordinary light
Constant to neighboring area.By the suitable technological parameter adjusting annealing external diffusion, the relative index of refraction corresponding to two kinds of polarization modes
Increment will reach unanimity, and then the normalization structural parameters of two polarization modes also tend to unanimously, and two patterns can be true at the same time
Protect hot spot under single mode to reach unanimity and match with optical fiber facula.Thus reaching low-loss, low pdl, can protect simultaneously again
The temperature stability of card insertion loss.
During waveguide chip with the inclined pigtail coupling of guarantor, if the spectrum width of light source is narrower, coherence length is longer, works as device
Two polarization modes optical path difference be less than light source coherence length when, two polarization modes will necessarily produce interference, affects device
The test accuracy of polarization crosstalk.Signal prison must be carried out using the wider low-coherence light source of spectrum width therefore in coupling process
Survey, the particularly detection of polarization crosstalk signal, to guarantee to protect between the stress axiss of inclined tail optical fiber and two polarization directions of chip
Corresponding relation.
The preparation process of the present invention low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator includes Lithium metaniobate light wave
Lead the bonding mistake that the preparation process of chip and first protects inclined pigtail assembly, the second inclined pigtail assembly of guarantor and lithium niobate fiber waveguide chip
Journey.
The preparation process of wherein lithium niobate fiber waveguide chip is as follows:
(1) choose x and cut y biography chip, by lithography stripping technique or wet etching photoetching process, form width in wafer surface
Spend for 4～8 μm, thickness be 60～85nm titanium film straight wave guide figure, the length direction of titanium bar is along the y direction of crystal.
(2) above-mentioned chip is put in diffusion furnace, be passed through wet oxygen simultaneously in diffusion furnace, the flow of wet oxygen is 1-2 liter/min
Clock；Carry out titanium diffusion under 1050 DEG C of high temperature, diffusion time is 3～5 hours；Form the titanium diffused waveguide area on Lithium metaniobate
(2).
(3) chip is carried out, then passes through lithography stripping technique or wet etching photoetching process again, in conjunction with pecvd
The growth of method silicon dioxide, the titanium dioxide that the titanium diffusion zone (2) being formed in wafer surface formation with the first step is completely superposed
Silicon graphicses, that is, silicon dioxide titanium diffused waveguide region (2) be completely covered, titanium dioxide silicon strip and titanium bar in step (1) need strict
Alignment, and width is identical, and the thickness of silicon dioxide is 100nm～200nm；
(4) place a wafer in annealing furnace, be passed through 2-4 liter/min of dry oxygen, anneal under 340 DEG C～360 DEG C of high temperature
External diffusion 5～8 hours；
(5) pass through the techniques such as photoetching, plated film and plating to be formed and titanium Luciola substriata strict alignment ti/au electricity in wafer surface
Pole figure shape；
(6) chip is cut, also will accompany piece 9 each bonding in chip two ends one is little after cleaning, then accompany together with little
Piece is ground polishing along the direction at 10 ° of angles, ultimately forms the parallelogram device chip (see figure 1) that acute angle is 80 °.
Need after having prepared lithium niobate fiber waveguide chip for chip and first to protect inclined pigtail assembly and the second inclined tail optical fiber group of guarantor
Part is of coupled connections, and needs to have using equipment during being of coupled connections: two sextuple micropositioning stages, slide holders, polarization is tunable
Light source, low polarization wide spectrum light source, extinction ratio tester, light power meter.Slide holder is mainly used to fixed chip, two sextuple fine settings
Frame is used for clamping optical fiber and can adjust the position of optical fiber and so that it is aligned with chip, polarizes tunable optical source offer aim detecting
Signal source, extinction ratio tester is aligned with the crystallographic axis of chip with determining the axial direction of optical fiber for monitoring extinction ratio signal, luminous power
Meter is mainly used to detect optical power signals to determine whether optical fiber is aligned with chip.
Wherein first protects the bonding process of inclined pigtail assembly, the second inclined pigtail assembly of guarantor and lithium niobate fiber waveguide chip such as
Under:
(1), two second are protected inclined pigtail assembly difference clamping on two sextuple micropositioning stages, the 4th step prepares niobium
Sour lithium chip of light waveguide clamping is on a slide holder；
(2), one of them second second polarization maintaining optical fibre 6a protecting in inclined pigtail assembly is accessed polarization tunable optical source, separately
Outer one second the second polarization maintaining optical fibre 6b protecting in inclined pigtail assembly accesses light power meter；
(3), adjust two sextuple micropositioning stage other five dimensions in addition to rotating along optical fiber axial direction, make described two second to protect partially
Optical fiber 6a, 6b are aligned with titanium diffused waveguide area 2；
(4), the second polarization maintaining optical fibre 6b is accessed after light power meter takes off extinction ratio tester, finely tune two second simultaneously
The axial-rotation of polarization maintaining optical fibre 6a, 6b, often finely tunes an axial-rotation, reads primary extinction than data, reads extinction ratio data
Method be: the polarization state of rotatory polarization tunable optical source one week, omit the symbol before extinction ratio tester registration, observation disappears
, than four maximum occurring successively on tester, described four maximum are as the absolute value of extinction ratio measurement value for light；
(5), repeat the 8th step, the absolute value of four extinction ratio data until recording reaches maximum；
(6), keep the axial-rotation of second polarization maintaining optical fibre 6a, 6b motionless, the second polarization maintaining optical fibre 6b is tested from extinction ratio
Instrument takes off and is followed by optical power meter, adjusts other five dimensions of the second polarization maintaining optical fibre (6a, 6b), until the luminous power that detects
Greatly；
(7), in the end face point ultraviolet glue of the second polarization maintaining optical fibre 6b, and adjust the second polarization maintaining optical fibre 6b again except axial-rotation
Other outer five dimensions, until the maximum optical power detecting；
(8), ultraviolet glue is exposed solidifying, completes the second polarization maintaining optical fibre 6b and lithium niobate fiber waveguide chip on slide holder
Being of coupled connections of one end；
(9), the second polarization maintaining optical fibre 6a is taken off from sextuple micropositioning stage, the first polarization maintaining optical fibre assembly is contained in described 6 DOF
On micropositioning stage；
(10), the first polarization maintaining optical fibre 5 in the first polarization maintaining optical fibre assembly is accessed low polarization wide spectrum light source, second is protected partially
Optical fiber 6b accesses light power meter；
(11), adjust the first polarization maintaining optical fibre 5 other five dimensions in addition to axial-rotation, make the first polarization maintaining optical fibre 5 and titanium diffusion
Region 2 is aligned；
(12), the second polarization maintaining optical fibre 6b is entered extinction ratio tester after light power meter takes off, fine setting is protected partially equipped with first
The sextuple micropositioning stage of optical fiber component, until the power that extinction ratio tester is measured is maximum, extinction ratio is minimum；
(13), in the end face point ultraviolet glue of the first polarization maintaining optical fibre 5, ultraviolet glue is exposed solidify, completes the first guarantor inclined
Optical fiber 5 and being of coupled connections of the lithium niobate fiber waveguide chip other end on slide holder.
Chips of the present invention are that device inputs the slow of polarization maintaining optical fibre with the core requirement of the concrete connection coupling process of optical fiber
Axle becomes about 45 ° of angles with the crystallographic axis of lithium columbate crystal, and the slow axis of output polarization maintaining optical fibre is mutually perpendicular to the crystallographic axis of lithium columbate crystal,
Preparation, the processing procedure of protecting inclined tail optical fiber are as follows:
(1), on silicon chip, pass through the method such as oxidation, photoetching, corrosion, form a series of V-shaped grooves, a diameter of for naked fibre
For 125 μm of the inclined tail optical fiber of guarantor, the width suitable for reading of V-shaped groove should be 170 μm～200 μm, and its depth is it is ensured that rear V-shaped put into by optical fiber
The two side of groove is tangent with optical fiber to be contacted, and then passes through cutting-up, forms the optical fiber fixed block 7,7 ' with V-shaped groove 8,8 '.(see figure
3).
(2), one end of polarization maintaining optical fibre is removed coat, then by the naked fibre exposed be bonded in an optical fiber fixed block 7,
In the V-shaped groove 8,8 ' on 7 ' surfaces, by observing the stressed zone of fiber end face it is ensured that the slow axis of optical fiber and V-shaped groove before bonding solidification
Axis of symmetry angle at 45 ° (see Fig. 4 a) in section or coincidence (see Fig. 4 b).
(3), optical fiber is carried out grinding and polishing together with optical fiber fixed block 7,7 ' by the direction at 15 ° of angles, the optical fiber ultimately forming
Illustrate as shown in Figure 5 and Figure 6, after being illustrated in figure 5 optical fiber and the fixed block polishing that the present invention is directed to lithium columbate crystal chip
View, the optical fiber being illustrated in figure 6 the present invention for lithium columbate crystal chip is illustrated with the state after fixed block polishing
Figure.
The above, the only optimal specific embodiment of the present invention, but protection scope of the present invention is not limited thereto,
Any those familiar with the art the invention discloses technical scope in, the change or replacement that can readily occur in,
All should be included within the scope of the present invention.
The content not being described in detail in description of the invention belongs to the known technology of professional and technical personnel in the field.
Claims (7)
1. low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator it is characterised in that: include lithium niobate fiber waveguide chip
Respectively coupling be bonded in lithium niobate fiber waveguide chip two ends first guarantor inclined pigtail assembly and second guarantor inclined pigtail assembly, first
Protecting inclined pigtail assembly is input, and second protects inclined pigtail assembly for outfan, and wherein lithium niobate fiber waveguide chip includes Lithium metaniobate
Substrate (1), titanium diffused waveguide area (2), annealing regions of out-diffusion (3) and metal electrode (4), lithium niobate substrate (1) is cut y using x and is passed
Chip, titanium diffusion zone (2) and annealing regions of out-diffusion (3) are located at the top layer of lithium niobate substrate (1), and regions of out-diffusion (3) of annealing
Positioned at the both sides of titanium diffusion zone (2), metal electrode (4) is located at the surface of annealing regions of out-diffusion (3), and positive and negative electrode is with regard to titanium
Diffusion zone (2) is symmetrical；The first inclined pigtail assembly of guarantor includes the first polarization maintaining optical fibre (5) and the first optical fiber fixed block (7), the first guarantor
Polarisation fibre (5) is bonded in the first V-shaped groove (8) on the first optical fiber fixed block (7) surface, and the second inclined pigtail assembly of guarantor includes second
Polarization maintaining optical fibre (6) and the second optical fiber fixed block (7 '), the second polarization maintaining optical fibre (6) is bonded in the second optical fiber fixed block (7 ') surface
In second V-shaped groove (8 ')；
The axis of symmetry angle in the slow axis of described first polarization maintaining optical fibre (5) and the first V-shaped groove (8) section is 45 °；Described second protects partially
The axis of symmetry angle in the slow axis of optical fiber (6) and the second V-shaped groove (8 ') section is 0 °.
2. low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator according to claim 1 it is characterised in that: institute
Stating the first optical fiber fixed block (7) and the second optical fiber fixed block (7 ') is rectangular blocks, and material is silicon crystal, a v on surface
Type groove (8) or the second V-shaped groove (8 ') are formed by wet etching.
3. low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator according to claim 1 it is characterised in that: institute
The width stating titanium diffusion zone (2) is 4～8 microns, and thickness is 2～6 microns.
4. low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator according to claim 1 it is characterised in that: institute
The thickness stating annealing regions of out-diffusion (3) is 2～6 microns.
5. low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator according to claim 1 it is characterised in that: institute
State the distance between positive and negative electrode in metal electrode (4) and be 10～20 microns.
6. the preparation method of the low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator described in claim 1, its feature
It is: include the preparation process of lithium niobate fiber waveguide chip and first and protect inclined pigtail assembly, the second inclined pigtail assembly of guarantor and niobic acid
The bonding process of lithium chip of light waveguide,
The preparation process of wherein lithium niobate fiber waveguide chip is as follows:
The first step, chooses x and cuts y biography lithium niobate crystal chip, by lithography stripping technique or wet etching photoetching process, in conjunction with titanium film
Growth, forms the straight wave guide figure of titanium film in wafer surface；
Second step, the chip after the first step is processed is put into and is carried out titanium diffusion in diffusion furnace, forms the titanium dilatation wave on Lithium metaniobate
Lead area (2)；
3rd step, the chip after second step is processed carries out, in non-titanium diffused waveguide region, external diffusion process of annealing, and forms annealing
Regions of out-diffusion (3)；
4th step, prepares metal electrode (4) on annealing regions of out-diffusion (3) surface, and makes metal electrode (4) with regard to titanium diffusion zone
(2) symmetrical, prepare lithium niobate fiber waveguide chip；
The bonding process of the wherein first inclined pigtail assembly of guarantor, the second inclined pigtail assembly of guarantor and lithium niobate fiber waveguide chip is as follows:
5th step, two second is protected inclined pigtail assembly difference clamping on two sextuple micropositioning stages, the 4th step prepares niobium
Sour lithium chip of light waveguide clamping is on a slide holder；
6th step, by one of them second protect inclined pigtail assembly in second polarization maintaining optical fibre a (6) access polarization tunable optical source,
The second polarization maintaining optical fibre b (6) that another one second is protected in inclined pigtail assembly accesses light power meter；
7th step, sextuple micropositioning stage other five dimensions in addition to rotating along optical fiber axial direction of regulation two, make described two second to protect partially
Optical fiber a, b (6) are aligned with titanium diffused waveguide area (2)；
8th step, the second polarization maintaining optical fibre b (6) is accessed extinction ratio tester after light power meter takes off, fine setting simultaneously two pieces the
The axial-rotation of two polarization maintaining optical fibre a, b (6), often finely tunes an axial-rotation, reads primary extinction than data, reads extinction ratio number
According to method be: the polarization state of rotatory polarization tunable optical source one week, observe four poles occurring successively on extinction ratio tester
Big value, described four maximum are as the absolute value of extinction ratio measurement value；
9th step, repetition the 8th step, the absolute value of four extinction ratio data until recording reaches maximum；
Tenth step, keep second polarization maintaining optical fibre a, b (6) axial-rotation motionless, by the second polarization maintaining optical fibre b (6) from extinction ratio survey
Examination instrument takes off and is followed by optical power meter, adjusts other five dimensions of second polarization maintaining optical fibre a, b (6), until the luminous power that detects
Greatly；
11st step, the second polarization maintaining optical fibre b (6) end face point ultraviolet glue, and adjust again the second polarization maintaining optical fibre b (6) remove axle
Other five dimensions to outside rotation, until the maximum optical power detecting；
12nd step, ultraviolet glue is exposed solidify, completes lithium niobate fiber waveguide on the second polarization maintaining optical fibre b (6) and slide holder
Being of coupled connections of chip one end；
13rd step, the second polarization maintaining optical fibre a (6) is taken off from sextuple micropositioning stage, the first polarization maintaining optical fibre assembly is contained in described
On sextuple micropositioning stage；
14th step, by the first polarization maintaining optical fibre assembly the first polarization maintaining optical fibre (5) access low polarization wide spectrum light source, by second protect
Polarisation fibre b (6) accesses light power meter；
15th step, regulation the first polarization maintaining optical fibre (5) other five dimensions in addition to axial-rotation, make the first polarization maintaining optical fibre (5) and titanium
Diffusion zone (2) is aligned；
16th step, the second polarization maintaining optical fibre b (6) is entered after light power meter takes off extinction ratio tester, fine setting is equipped with the first guarantor
The sextuple micropositioning stage of inclined optical fiber component, until the power that extinction ratio tester is measured is maximum, extinction ratio is minimum；
17th step, the first polarization maintaining optical fibre (5) end face point ultraviolet glue, ultraviolet glue is exposed solidify, complete the first guarantor
Polarisation fibre (5) and being of coupled connections of the lithium niobate fiber waveguide chip other end on slide holder.
7. the preparation method of the low Polarization Dependent Loss Lithium metaniobate vertical bar Waveguide Phase Modulator described in claim 6, its feature
It is: described 3rd step carries out, in non-titanium diffused waveguide region, external diffusion process of annealing to chip, forms annealing regions of out-diffusion (3)
Specifically comprise the following steps that
(1) chip after, processing second step is carried out, and forms the titanium diffusion zone with formation in the first step in wafer surface
(2) silicon dioxide pattern being completely superposed, that is, silicon dioxide titanium diffused waveguide region (2) is completely covered；
(2), place a wafer in annealing furnace, annealed under conditions of logical oxygen, form annealing regions of out-diffusion (3).
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| JP6075347B2 (en) * | 2014-09-30 | 2017-02-08 | 住友大阪セメント株式会社 | Optical device |
| CN104597551B (en) * | 2015-02-26 | 2017-07-28 | 中国电子科技集团公司第四十四研究所 | Polarizer of high polarization extinction ratio and preparation method thereof and test device can be achieved |
| CN105739133B (en) * | 2016-05-05 | 2018-11-02 | 中国电子科技集团公司第四十四研究所 | The modulation efficiency low frequency electro-optic phase modulator unrelated with polarization |
| CN105739134B (en) * | 2016-05-05 | 2018-08-10 | 中国电子科技集团公司第四十四研究所 | The modulation efficiency high frequency electro-optic phase modulator unrelated with polarization |
| CN108732795A (en) * | 2017-04-14 | 2018-11-02 | 天津领芯科技发展有限公司 | A kind of silicon substrate lithium niobate high-speed optical modulator and preparation method thereof |
| CN109613648B (en) * | 2019-02-14 | 2020-04-10 | 聊城大学 | Preparation method of full-crystal waveguide coupler |
| CN110646957A (en) * | 2019-08-05 | 2020-01-03 | 天津领芯科技发展有限公司 | Novel lithium niobate electro-optical modulator based on zinc oxide waveguide and preparation method thereof |
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