CN1771446A - Beam shaping and practical methods of reducing loss associated with mating external sources and optics to thin silicon waveguides - Google Patents

Abstract

A practical realization for achieving and maintaining high-efficiency transfer of light from input and output free-space optics to a high-index waveguide of submicron thickness is described. The required optical elements and methods of fabricating, aligning, and assembling these elements are discussed. Maintaining high coupling efficiency reliably over realistic ranges of device operating parameters is discussed in the context of the preferred embodiments.

Description

Beam shaping and reduce the practical approach that external light source and optical device is connected to the loss that the thin silicon waveguide causes

Quote with the cross-reference of related application

The present invention requires the provisional application No.60/461 of submission on April 10th, 2003,697 rights and interests.

Technical field

The present invention relates to the coupling device relevant with the thin silicon optical waveguide, particularly with beam shaping with reduce the method that external light source and optical device is connected the loss that causes with this thin-film guide.

Background technology

In the application of many equipment, input signal must be done pre-service in equipment, so that the equipment proprietary technology of implementing basic function is optimized; Equally, be transferred to before the outside, the signal that sends in the slave unit core must be made post-processed, so as to produce one with the compatible signal of typical user's demand.For photoelectric subassembly, required optical signalling is handled and is comprised light generation, wavelength control, Polarization Control, phase control, beam direction control, beam shaping, beam separation or functions such as compound, modulation and detection.For the convenience on using, perhaps, generally many pre-service or post-processed function can be integrated in the assembly in order to control for the vital parameter of equipment performance.For example, an important benefit is by more optical function is integrated in the assembly, can reduce the optical insertion loss of equipment usually.This is not only because selection of components can more easily be optimized the equipment proprietary technology, also because the physical connection of distinct device or inter-module is reduced.Can use a kind of low-loss photoelectricity assembly in the system applies, because its easier different place that are applied in system, and the range of application of expansion system.In addition, can reduce the physical size of equipment by equipment integration.

Pre-service and post-processed optical function integrated particularly crucial for the silicon-based optoelectronic circuits that is operated in infrared wavelength.Because also be extensive use of the silicon laser instrument in commercial the application, now also can't image signal handle and receiving element is introduced light source like that in same silicon chip.Therefore, light signal must be incorporated into the silicon chip from external light source.This needs (between light source and waveguide) to insert optical element so that signal is done pre-service, so that there is the light of suitable intensity can transfer to waveguide.In addition, just begun exploitation because be suitable for the silicon-based detector of infrared wavelength, light signal must be from the silicon waveguide to outer locator or receiving element.Therefore, the output terminal of equipment needs optical element optical signalling is made post-processed.The typical method that in the prior art optically-coupled is entered high-index contrast waveguides comprises the fibre-optic terminus or the lens-type optical fiber of prism coupler, grating coupler, tapered mode converters and special shape.Though all these optical elements all have been used for the waveguide from a part of light transmission to a high-index contrast of external light source, when being used to the prototype of low-loss equipment or final products, these parts still have a lot of restrictions under laboratory environment.

For example, the tuftlet spot size that the fibre-optic terminus of special shape, lens-type optical fiber or tapered mode converters can produce is about 1.5 μ m, and the silicon waveguide of this and some submicron-scales does not match.Especially, need size to be about 0.35 μ m or littler monotype silicon waveguide in many application.The mode field diameter and the mismatch between the mode field diameter under the waveguide mode of the output beam of specialty optical fiber or tapered mode converters will cause high insertion loss.Even the diameter of waveguide is about several microns, because the input and output port of equipment must be positioned on the cut surface of the wafer die that has comprised waveguide, when device coupled arrived specialty optical fiber or tapered mode converters, the geometric configuration of equipment (for example, the layout of equipment and size) had a lot of restrictions.

Above-mentioned restriction can be solved by with grating coupler or prism coupler light being coupled into the high-index contrast waveguides or therefrom being coupled out from external light source.By suitable design, can successfully will couple light to the waveguide of thickness range from tens nanometer to tens of microns.In addition, grating or prism element can be placed in the position of mould or wafer surface any appropriate, make light can enter mould or the sizable part of wafer.

Though they have quite a lot of advantage, the difficulty in grating and the prism coupler manufacturing has still limited their application in some special applications.The coupling efficiency of grating coupler is responsive for grating cycle, the degree of depth and pitch angle.In theory, if the design object of grating parameter can satisfy, can obtain the coupling efficiency of about 70-80%; In fact, owing to the susceptibility for manufacturing tolerance, the coupling efficiency of actual measurement is many about 40%.

In prior art, prism coupler need be placed in a big bulk-optic element (being of a size of several millimeters) very and accurately locate near the position and the relative waveguide of waveguide.Here, " very approaching " is meant that the spacing between optical element and waveguide allows the evanescent wave coupling of light from the optical element to the waveguide.For the infrared wavelength that uses in the telecommunications applications, typical distance values drops in the scope of 200-500nm.The required motion control (for example, using piezoelectric mounts) of waveguide manipulation prism can be finished in breadboard optical table or proving installation relatively, but this method can't realize in compact optoelectronic package.Therefore, prism-coupled is used major limitation in the waveguide test and identifying.

Because prism coupler be not applied to compact optoelectronic package in prior art, be suitable for the mini-plant structure in the prism coupler optics and the mechanical part that are used also do not develop.For example, openly do not transport light to the prism coupler mount in the compact optoelectronic package or therefrom receive the specific embodiment of the exemplary optical elements of light in the prior art.In lab setup, change (as the variation of wavelength, polarization state, light-beam position, incident angle etc.) when certain takes place the signal of introducing prism coupler, generally can adjust optical element to optimize the signal transmission with multiple mode.For midget plant, be suitable for designing one for all transparent device of multiple input; That is to say, when the input state of signal changes, only need to adjust fraction parameter (or not needing to adjust) for making the device operate as normal.Therefore, the selection of the optical parametric relevant with input and output light beam, input and output optical element and prism coupler has directly influenced the versatility and the manufacturability of device.Yet,, also do not have exploitation to be used to make the detailed design scheme of the devices of using and can making because prism coupler also is not integrated in the low profile photovoltaic device in prior art more.

Therefore, the optical system that also needs in the present technique to design and realize to dock with the prism coupler in small-sized, low-loss, the stable photoelectric subassembly.

Summary of the invention

The demand that waits in the prior art to solve will be illustrated in the present invention that it has related to Design for optical system, and this system can be used to handle and enters the small-sized prism coupling light electric installation and the infrared signal of outgoing therefrom.

Especially, the detailed description of the invention embodiment of several optical elements that provide necessary interface for the small-sized prism and the waveguide elements of permanent coupling.These interfaces including, but not limited to: light is caused optical element or the structure that free space optical elements the high index prism structure, etching face make as the same silicon chip or the mould of prism input and output face, the evanescent that has constituted the direct physical interface between high index prism and waveguide from external light source, and receives from the free space optical elements of the output beam of prism output face outgoing.

Above-mentioned various embodiment is particularly suitable for the thin silicon waveguide in the wavelength band commonly used in the telecommunication application.Yet the various interface device among the present invention equally also can be used for other devices, and can use larger sized waveguide and/or other wavelength coverages.Describe the specific embodiment of transmitting optics device and the condition that new and compact encapsulation scheme is provided for the prism-coupled device in detail.Disclose and the end-to-end insertion loss of using the low profile photovoltaic device of prism-coupled can be reduced to minimum design proposal, and calculated the theoretical coupling efficiency of specific embodiment.Advantageously, the embodiment that describes the concrete of the evanescent that can produce desirable output beam intensity distributions and reduce insert loss in detail and can make.

With reference to the accompanying drawings, in ensuing declarative procedure, will display with respect to making the advantage that needs to reduce required free space beam size.

Description of drawings

Please refer to accompanying drawing now.

Fig. 1 shows a kind of silica-based prism coupler, and this coupling mechanism is permanently affixed at a wafer that comprises the silicon-on-insulator (SOI) of a silicon ducting layer.

Fig. 2 shows the geometric course that a branch of light is propagated in a prism structure, comprise that the inside and outside emission angle of prism (corresponds respectively to θ _AirAnd θ _Si), and the physical size in the optical coupled zone at prism surface place, this prism surface directly links to each other with evanescent;

Fig. 3 has shown the external beam emission angle theta of the prism of embodiment among Fig. 1 _SiIn certain telecommunication wavelength coverage, and the scope under three Different Silicon duct thickness conditions;

Fig. 4 has shown the aerial beam emissions of embodiment angle θ among Fig. 1 _Air(in the prism outside) scope in certain telecommunication wavelength coverage and under three Different Silicon duct thickness conditions;

Fig. 5 has shown prism structure inside (θ _Si) and prism facets (θ _Air) four corner of outside emission angle, covered the device silicon layer thickness scope of 0.1 to 0.21 μ m and 1290 to 1590nm wavelength coverage;

Fig. 6 shows the coupling efficiency curve and is covering certain free space input beam diameter value and three different coupling constant values

Under the angle halfwidth (with FWHM (θ _Air) expression);

Fig. 7 has shown the function of the coupling efficiency of the embodiment among Fig. 1 as the monox evanescent layer thickness, the analog result in the wafer of silicon-on-insulator under three kinds of different waveguide layer thicknesses;

Fig. 8 has shown for the coupling efficiency of the embodiment similar to the embodiment among Fig. 1 function as evanescent layer thickness, for the analog result of three kinds of different materials forming evanescent.

Fig. 9 has shown the curve of the peak excursion of flatness (being called " key groove ") as free space input beam diameter, and the theoretical model of the constant thickness of the evanescent of embodiment is consistent among this flatness and Fig. 1.

Figure 10 shown to Fig. 1 in the similar and best key groove of embodiment that has a wedge shape evanescent as the function of free space input beam diameter.

Figure 11 shows the prism-coupled face in certain telecommunication wavelength coverage for the embodiment among Fig. 1

On input beam size and input free space beam size

Ratio, the situation in the SOI wafer under four kinds of different waveguide layer thicknesses;

Figure 12 (a) and (b) to show an initial unpolarized input beam with top view perspective view and side-looking perspective view be how to be converted into two independent light beams on the required polarization direction, thereby allow that light is coupled into waveguide expeditiously by a prism structure;

Figure 13 has shown to use and has actuated MEM micro-reflector control bundle is emitted to the suitable emission angle of prism outside from a horizontal light source example.

Figure 14 has shown a kind of physical layout, and this layout has been showed the side-emitted of the light of the edge-emitting diode of drawing from an optical fiber or other optical fiber input access to plant, and output terminal is in an opposite side of assembly;

Figure 15 has shown a kind of physical layout, and this layout has been showed the side-emitted of the light of the edge-emitting diode of drawing from an optical fiber or other optical fiber input access to plant, and output terminal is in the same side of assembly;

Figure 16 has shown and has used array VCSEL light source and the microprism array example with beam direction to a prism structure;

Figure 17 is the another kind of embodiment of the device of Figure 16, wherein used an edge-emitting diode array to replace into the VCSEL light sources of row;

Figure 18 is and the similar another kind of embodiment of Figure 16, and used one group to unite the lens-type optical fiber of arrangement with the Beam Control device;

Figure 19 has shown a prism wafer, and this wafer has comprised the additional optics of calibrating and handled light beam before the evanescent interface;

Figure 20 (a) has shown the preferred embodiment of Fig. 1, this embodiment has the evanescent of constant thickness, Figure 20 (b) and (c) shown that the curve of input and output light beam vibration amplitude as the function of z, Figure 20 (d) have shown Figure 20 (b) and (c) stack of (c);

Figure 21 has comprised a synoptic diagram that has shown a kind of special device of formation one and half high bass waves; And

Figure 22 (a) has shown the preferred embodiment of Fig. 1, the evanescent of this embodiment tape thickness linear change, and Figure 22 (b) and (c) shown the curve of input and output light beam vibration amplitude as the function of z, Figure 22 (d) has shown Figure 22 (b) and stack (c);

Embodiment

In order to understand purport of the present invention better, it is very important to understand the demand relevant with input beam, and this input beam at first is transferred to the input face of the typical prism structure 10 that shows among Fig. 1, is coupled to a thin silicon waveguide 12 by prism structure then.The detailed schematic diagram that input beam is propagated in prism structure has been shown among Fig. 2.This light beam enters prism structure 10 by hypotenuse (input face) surface 14, and this surface has been coated and put reflection horizon 16 to reduce the Fresnel loss that is caused by the transmission of (silicon among the embodiment Fig. 1) from low refractive index dielectric (atmosphere) to high refractive index medium.With reference to Fig. 2, input beam becomes incident angle θ with the normal direction on plane of incidence surface 14 _Air, then by prismatic refraction.For consistent, with the angle (θ in the prism with known optics _Si) represent with a light beam and vertical with a waveguide axle angulation the most convenient.According to the geometric relationship of Fig. 2, θ _SiAnd θ _AirFollowing relation is arranged:

θ _Si＝θ _pr-sin ^-1{sinθ _air/n _Si}，

Wherein for the wavelength n in the 1.3-1.6 mu m waveband _Si=silicon refractive index ≈ 3.5.

Refraction has enlarged the size of prism inner light beam simultaneously, and along axle shown in Figure 2, sampling factor is:

For coupling efficiency, the projection of this light beam on prism and evanescent interface is crucial parameter.As seen, input free space beam and diameter are from the geometric relationship relevant with Fig. 2 The free space input beam can be expressed as in the relation of the lip-deep projection of prism-coupled:

Fig. 2 illustrates how much restrictions of the propagation of control prism 10 inside and outside light beams, and Fig. 1 has then shown a kind of preferable layout, and wherein prism coupler is made by a silicon wafer, and is permanently affixed on the SOI wafer 20 of a connection that has comprised waveguide 12.As shown in Figure 1, ducting layer 12 separates by a barrier oxide layer 24 with silicon substrate 22.Required prism surface is made on silicon wafer by uniting wiring and etching process, rather than uses a discrete accurate prism optical element.The part of required vertical wall 30,32 can be made by multiple etching processing, makes by the anisotropic wet etching treatment and prism inclined-plane 14,18 is the easiest.Anisotropic is handled has different etch rates for different crystal faces, thereby prism inclined-plane 14,18 becomes specific angle with wafer plane.For the structure among Fig. 1, the silicon prism wafer be＜100〉crystal orientation, thereby anisotropic KOH etching will obtain becoming with wafer plane the crystal face of 54.74 degree angles.By on the top waveguide surface of the SOI of silicon prism wafer or connection crystal face, depositing one deck refractive index less than silicon refractive index (n _Si≈ 3.5) material, can obtain an evanescent 26.Then, prism coupler forever links to each other with the SOI wafer that has comprised waveguide, though bonding agent and solder joints method also can be used, preferably uses semiconductor to engage disposal route.In the prism coupler that obtains/SOI wafer components, the substrate of prism coupler 10 (prism-coupled surface 15) directly contacts with the waveguide surface 12 of SOI wafer 20, can obtain the interlayer of a prism/evanescent/waveguide like this.In order to reduce the Fresnel loss at input and output prism chamfered surface place (hereinafter referred to as " prism facets "), deposited the additional material of one deck (or multilayer) on the surface of the silicon prism coupler of integrated prism facets.This one deck or sandwich construction are penetrated coating 16 as putting back, and this coating can significantly improve transmissivity when light crossed prism facets.

By using the well-known theory in the prior art, the beam angle θ in the silicon prism structure _SiCan in the certain duct thickness scope compatible and in the wavelength range of telecommunication application use, calculate with the monotype propagation.Duct thickness is that 0.1,0.14 and 0.21 μ m and wavelength coverage are the θ of 1290-1630nm _SiResult of calculation be presented among Fig. 3.Selected these typical duct thickness to be because optics can be integrated in these relative very thin waveguides with the high-velocity electrons function.As can be seen, beam angle θ _Si(defining among Fig. 2) covered the scope of 38 degree to 58 degree in required wavelength and duct thickness scope.For the emission angle theta of determining that prism is outside suitable _Air, can use the θ that had before obtained _SiAnd θ _AirRelation.As described above, for the embodiment among Fig. 1, for＜100〉silicon wafer of orientation, use to produce input and output and become the anisotropic etching processing of the face at angle will obtain θ _Pr=54.74 degree.Yet the use of the embodiment among Fig. 1 is not limited thereto specific θ _PrValue; The θ that also can use arbitrarily other to obtain by etching processing or distinct methods _PrValue.Fig. 4 has shown that wavelength coverage is at 1290-1630nm scope and duct thickness θ during at 0.10,0.14 and 0.21 μ m _AirResult of calculation.The scope of incident angle is much bigger in the air, spends in 90 degree-15 to change; This is because the refractive index of air (n ≈ 1.0) and silicon (n ≈ 3.5) differs bigger.

Fig. 5 provides a kind of prism inside (θ _Si) and prism outside (θ _Air) the diagrammatic representation of angular range, for the prisms of 54.74 degree, this angular range must reach, so that make the use of equipment can cover the gamut of wavelength and duct thickness.Except that can not using greater than the wavelength of 1590nm for the duct thickness of 0.10 μ m, the air launching condition can be realized in very wide wavelength and duct thickness scope.Therefore, the major advantage of embodiment shown in Fig. 1 comprises that semiconductor wires, etching and joining process that (1) coordinates to use always produce prism coupler and the waveguide assembly that can make, and (2) constitute a kind of useful structure, and this structure can be used for covering the application of infrared wavelength and duct thickness on a large scale.

The input that the purposes of device illustrated in fig. 1 can be by selecting to simplify the optical signal interface that is connected to the device among Fig. 1 and the optics of input beam and spatial character and further strengthen.Because by practical application decision, can assembly in adjust usually by polarization direction, beam shape, light beam (or wavefront) quality and the direction of propagation for the power of wavelength coverage and input signal.Use for Lens Coupling, according to the present invention, it is necessary accurately controlling these parameters, so that the expection high coupling efficiency that light obtains when the Lens Coupling device is to waveguide.Especially, following condition must satisfy:

(1) input beam must be from the incident angle outgoing by the refractive index decision of the refractive index of the polarization state of input beam and wavelength, silicon device ducting layer 12 (following represent with W) and evanescent 26 and thickness and prism 10 and its surrounding medium.If incident beam is from suitable incident angle outgoing, the wave field propagation constant in prism 10 and the waveguide 12 will be mated, and make to obtain high coupling efficiency.

(2) light beam must be on prism-coupled surface 15 place's height collimations, the thinnest part of importing Gaussian beam like this dropped on the prism-coupled surface near.Know that if the phase place of wavefront alters a great deal, coupling efficiency can reduce in the drop shadow spread of ripple on prism-coupled surface 15.

(3) input beam must intersect in a certain location and prism-coupled surface 15, and this depends on the form of evanescent and the beam intensity of input optical signal.For the evanescent 26 of Gauss's input beam and constant thickness, as can be seen, light beam must be arranged in vertical sidewall 34 distances of leaving the prism that Fig. 2 shows in the lip-deep projection centre of prism-coupled and be

The position on so that coupling efficiency maximization.The sub-fraction quilt internal reflection fully that light beam is blocked by vertical sidewall 34 is before output face 18 outgoing, at first by vertical sidewall 34 reflections, then by 15 reflections of prism-coupled surface.It is emphasized that this position relatively Little skew can make coupling efficiency reduce (about 10%) slightly.Block the projection of input beam on prism-coupled surface 15 with this special mode, prevented that the optically-coupled that transfers to waveguide 12 from prism structure from getting back to prism structure.

(4) in order to make the coupling efficiency maximization, the thickness of evanescent wave layer must be suitable for the size of input beam in the lip-deep projection of prism-coupled,

From prior art, know, (be about by the projection that realizes input beam

And mainly by a kind of particular kind of relationship between the stiffness of coupling parameter (after this being called " α ") of evanescent wave layer thickness decision, it is maximum that coupling efficiency can reach.This be because α and Be the important parameter in the overlap integral, this overlap integral has determined coupling efficiency.

In order to satisfy these conditions in compact optoelectronic package, suitable collimation, shaping and light beam weigh the guide miniature element, and extra polarization and phase control optical device, and be very important for the coupling efficiency that optically-coupled is entered the structure among Fig. 1.Because the typical sizes of prism facets is about the 0.5-1.0 millimeter among Fig. 1, the size of the diaphragm of optical element must be similar, to keep whole assembly compactness.The full-size of light beam must be slightly smaller than the size of optical element, to prevent causing transmission loss because of light beam is limited.Will discuss below, other manufacturing factors of using specific to prism-coupled have applied more strict restrictions on the full-size of light beam.For efficient prism coupling, exists an optimum laser beam size (relevant with the character of evanescent, as previously mentioned) and a minimum beam size, cross prism structure and can keep collimating when crossing when light beam like this with prism-coupled is surperficial.

If selected a suitable largest beam size, the manufacturing tolerance of device as shown in fig. 1 is easier to be met.Especially, can obtain the remarkable advantage of tolerance aspect of the thickness of the emission angle of input beam I and evanescent 26.

From prior art, know, for the evanescent of constant thickness, when

The time, can obtain 80% optimistic coupling efficiency.α is the parameter of expression stiffness of coupling, also is that unit is the contrary of length from the characteristic constant of the shape of the light beam of the output face outgoing of prism structure, and the form of the shape of outgoing beam is g (z) ∝ exp (α z).The phase change decision that parameter alpha is mainly caused by the reflection of the propagation constant in evanescent layer thickness, the evanescent and two boundaries of waveguide.

Optimize coupling if be made as 0.68, so because

Value reduces, and α must increase, and is equivalent to stronger coupling or thinner evanescent.The stiffness of coupling that strengthens causes wideer resonance, and wideer resonance allows wideer wavelength coverage or import angle equivalently to be coupled into waveguide.In fact, the halfwidth (FWHM) of the Lorentz distribution plan of (β represents propagation constant) resonance directly is proportional to α in the β space, and the pass is:

FWHM (β)=FWHM (n _SiSin θ _Si)=α λ/π. molecule and denominator multiply by

And according to following relation:

θ _Si=θ _Pr-sin ^-1{ sin θ _Air/ n _Si, can draw halfwidth as input angle θ _AirFunction be:

Wherein,

F(θ _air，θ _pr){1-(sinθ _air/n _Si) ²} ^1/2/[cos(θ _air)×cos{θ _pr-sin ^-1(sinθ _air/n _Si)}].

For a kind of specific device construction, for example shown in Fig. 1, θ _PrAnd W (duct thickness) is respectively the amount (θ that fixes _Pr) ₀And W ₀In addition, if selected certain wavelengths λ ₀, θ then _AirCentral value also be set in a specific value (θ _Air) 0 (as shown in Figure 4).In this case, with respect to θ _AirThe intensity halfwidth of the little deviation of (entering the external emission angle of prism structure) can be expressed as:

This expression, the intensity distributions in certain input angle scope is along with the parameter of decision coupling efficiency

Linear increasing, and along with the inverse of the projection of beam diameter on prism-coupled surface 15 increases.For a given coupling efficiency Value, the intensity distributions in certain input angle scope can strengthen by the projection of diameter on prism-coupled surface 15 that reduces input beam.Improve coupling constant equally, slightly

Value, the intensity distributions in certain input angle scope can be improved, and coupling efficiency only descends slightly.Consider from manufacture view, select suitable coupling constant And light beam projecting Very important, so as final device in its operating period for little θ _AirChange more stable.Below an example show the beam sizes that is suitable for high coupling efficiency and the variation range of input angle.

Fig. 6 has shown FWHM (θ _Air) as four free space optical beam diameters

Value and three different coupling efficiencies

The function of value.The beam sizes of these four selections is corresponding to following situation: (1) 63 μ m: the standard output beam size of lens-type optical fiber components; (2) 100 μ m: the integrated typical beam size of lenticular vertical cavity surface emitting laser (VCSEL) in the laser module; (3) 200 μ m: obtainable minimum beam size in the standard fiber optics collimator (the fiber/ferrule parts that align with a GRIN or aspheric mirror); And (4) 360 μ m: the beam sizes of normal use in the standard fiber optics collimator (the fiber/ferrule parts that align with a GRIN or aspheric mirror).In order to calculate coupling efficiency and the halfwidth under the variation of input emission angle, light beam is in the lip-deep projection of prism-coupled

With the formula of front from the free space optical beam diameter

Calculate.Next consider by adjusting

Value change the influence of coupling efficiency.If evanescent is thicker than the optimum value of given beam sizes, system will be in the undercoupling state, promptly

Less than optimum value.For For the embodiment among Fig. 1, still can obtain 72% coupling efficiency.For the tolerance of input angle, this situation is not very suitable, and reason is that resonance is more sharp keen, and θ _AirThe tolerance that changes is less than the tolerance under the optimum coupling condition.For the device that is operated among Fig. 1 under the 1550nm wavelength, 72% coupling efficiency is corresponding to the blocked up evanescent (see figure 7) of about 40nm under the undercoupling condition.As can be seen, under this coupling value for any attainable structure, FWHM (θ _Air) generally be no more than 0.35 the degree.Under the optimum coupling condition, The time FWHM (θ _Air) increased to the 0.4-0.6 degree, then be maintained at about the 0.1-0.2 degree for bigger beam diameter.Consider the situation that the about 40nm of evanescent is thin excessively now, coupling efficiency then occurring is 72%, The overcoupling situation.As can be seen from Figure 6, for

The angle tolerance has significantly improved the degree to 0.7-1.1, then reaches about 0.2-0.35 degree for bigger beam diameter.Therefore, after the Free Space Optics device calibration, when using little beam diameter can significantly reduce device in the device of appropriate overcoupling or the sensitivity of the little variation that produces when aging of device to work.

Use other benefits of less relatively beam diameter to derive from light beam and the interactional limited physical degree of evanescent.For obtaining high coupling efficiency, the thickness of evanescent is control accurately.The variation of bed thickness can be converted into the variation of α, makes

Value depart from optimum value 0.68.As an example, the coupling efficiency that has shown the preferred embodiment among Fig. 1 among Fig. 7 under three kinds of ducting layer 12 different thickness as the function of the thickness of monox evanescent 26.The thickness of evanescent is estimated with reference to the input free space beam that application wavelength and the diameter of 1550nm is 63 μ m.The scope of device shown bed thickness has been represented the actual distribution scope of the bed thickness in the present silicon-on-insulator processing among the figure.Target device layer thickness is 0.14 μ m, as shown in preferred embodiment.As seen from the figure, the thickness of evanescent must drop in the scope of desired value ± 20nm, is about 320nm in this example, reduces by 10% (if considering the tolerance of the thickness of ducting layer 12, ± 0.01 μ m) to prevent coupling efficiency.However, the tolerance of ± 20nm must be kept in the whole physical extent of light beam in the lip-deep projection of prism-coupled, to guarantee high coupling efficiency.This condition is easier being met, if (1) selects to constitute the medium of evanescent, makes that the width of the coupling efficiency curve among Fig. 7 is suitable; (2) disposal route that prism coupler is fixed on the waveguide surface of SOI wafer makes thickness tolerance be kept in the physical extent of light beam projecting; And (3) light beam is relatively very little in the physical extent of the lip-deep projection of prism-coupled.

Fig. 8 has shown a kind of analysis result similar to Fig. 1, but has shown coupling efficiency function as evanescent layer thickness under three kinds of different evanescent refraction coefficients.These three values have been represented three kinds of different typical medias: air (n ≈ 1.0), monox (n ≈ 1.45), and silicon nitride (n ≈ 2.0).The citation form of the coupling efficiency curve under these three kinds of situations is identical, but clearly best evanescent layer thickness changes, and the width of coupling efficiency curve increases along with the refraction coefficient of evanescent and broadening slightly.With reference to Fig. 8, during n=2.0, the thickness of evanescent must drop in the scope of desired value ± 20nm, about 385nm in this example, to prevent that coupling efficiency from reducing by 10% (if considering the thickness tolerance of silicon ducting layer (with reference to the ducting layer mark of figure 1), ± 0.01 μ m).Therefore, using more, the evanescent of high index of refraction can obtain small benefits.What is interesting is that as long as obtained correct evanescent layer thickness, these three kinds of media (air, silicon dioxide, and silicon nitride) are worked well in the scope of current embodiment.(monox is ± 20nm to the connecting curve width that marks, and silicon nitride be ± 25nm) corresponding to the tolerance of evanescent layer thickness ± 6-7%, and this value is mated with present technique manufacturing method.

For the device construction shown in Fig. 1, if a beam diameter The free space input beam that is 63 μ m is transferred on the input prism facets, and input beam is at coupled surface On the full-size of projection be about 110 μ m (for wavelength is 1550nm, and duct thickness is 0.14 μ m, the about 320nm of monox evanescent layer thickness).In addition, as seen from Figure 7, the thickness variable ± 20nm of evanescent, and still can keep surpassing 70% coupling efficiency for identical device construction.In the device fabrication, the prism-coupled surface generally is not an absolute parallel with planar waveguide.The little skew of opposing parallel position will cause that the amplitude of evanescent layer thickness changes along the prism-coupled surface is slight.Fig. 9 has demonstrated for as showing embodiment among Fig. 1, the skew of supported opposing parallel position in certain input beam range of size, but still consistent with a kind of model of uniform thickness evanescent.As shown in Figure 7,, can support maximum ± 20nm in the optically-coupled zone for evanescent as the constant in fact coupling regime of thickness, or total 40nm variation in thickness.Therefore, if input beam at the lip-deep 110 μ m that are projected as of prism-coupled, the maximum key groove of permission is about 0.04 μ m/110 μ m=4 * 10 ^-4Radian or 0.02 degree.If used the silicon nitride evanescent, do similarly to calculate as can be known, be the free space beam of 62 μ m for diameter, the maximum offset of the flatness of permission can suitably increase to 0.026 degree.If used large-sized light beam, the optimum thickness of evanescent will increase, but allow the variation of the thickness of high coupling efficiency to remain unchanged substantially, be about ± 20nm.Free space beam size for 360 μ m

For the device construction among Fig. 1, corresponding light beam is about 610 μ m in the projection of prism surface.Similar calculating provides, and the key groove of permission has been reduced to 0.04 μ m/610 μ m=6.6 * 10 ^-5Radian, or 0.004 degree.The improvement of most of key groove tolerance comes from the following fact, and promptly the gap clearance for less beam sizes key need keep in small range.Because the key groove of above-mentioned all permissions is all very little, and along with light beam oppositely reduces in the lip-deep projection of prism-coupled, the manufacturing of the equipment of the coupling light expeditiously that shows among Fig. 1 has significantly improved owing to used the design proposal of less relatively beam sizes.

In a kind of variant of the device construction shown in Fig. 1, evanescent layer thickness can make coupling efficiency promote above 80% along the little variation in input and output optically-coupled zone.Known from prior art, the gradient thickness of evanescent makes the intensity of output free space beam be essentially Gaussian, greater than optimum thickness, and the thickness in the place that the last residue light intensity of optically-coupled zone in waveguide separated by output prism is less than optimum thickness at the thickness in the place that light beam is at first separated from waveguide by output prism in the optically-coupled zone.This situation with the evanescent of constant thickness is different, and the output beam intensity distributions under the constant thickness situation is an exponential form.The improvement of Gauss's input beam that the evanescent of wedge shape is brought and the output beam inter mode coupling that is essentially Gaussian makes theoretical coupling efficiency bring up to about 97% from 80%.If there is not detailed mathematical discussion, the essential information that is used for calculating the proper angle of Figure 10 wedge shape can obtain from Fig. 7.As previously mentioned, relevant with stiffness of coupling and appear at parameter alpha in the functional form of output beam intensity distributions, mainly by the thickness decision of evanescent.For the wedge shape evanescent that the direction of propagation of thickness (z) light in the waveguide changes, the stiffness of coupling at given z value place then directly and α, the local value of α (z) is relevant.The thickness of evanescent must approximate input beam at one and become strong coupling (big α (z)) from weak coupling (little α (z)) in the distance scale of the lip-deep projection of prism-coupled.For obtaining high coupling efficiency, need determine suitable average thickness values (this produces the α value near the optimum value of α, and this value is suitable for the optimum coupling of constant thickness evanescent) and thickness suitable linear change along with z, or " key groove ".For the example of Fig. 7, during W=0.14 μ m, coupling efficiency has dropped to its peaked about 37% (or 1/e) and has located when evanescent wave thickness is 250nm and 450nm as can be seen.This is corresponding to crossing the projection of light beam on the coupled surface variation of 200nm altogether.For embodiment among Fig. 1 and the structure shown in Fig. 7, when the total projection beam length was 110 μ m, the electric field amplitude of the projection of output beam on coupled surface was from the distance peak value The place drops to its peaked about 37% place.Detailed overlap integral from generalized theory and prior art can infer that this coupling will cause the high superposed between output and input beam.So the optimum gradient in linear change gap is 200nm/100 μ m=1.8 * 10 ^-3Rad=0.1 °.It should be noted that this condition also is suitable for for less relatively (but still can reach) free space diameter of 63 μ m.If used silicon nitride (Fig. 8, n ≈ 2.0) rather than monox evanescent, be the free space beam of 63 μ m for diameter, optimum gradient suitably increases to 0.13 °.

Figure 10 has shown the beam sizes of using in the result of calculation that shows among Fig. 9 has been done identical calculating that the best key groove that obtains is as the function of free space beam size.It should be noted that best key groove has increased 6-7 doubly, when when free space beam is of a size of 360 μ m 0.02 ° is increased to free space beam and is of a size of 63 μ m 0.10 °.Equally, the improvement of tolerance mainly is because need keep accurate variation in thickness for littler beam sizes in a littler distance range.

Because the required key groove of constant thickness and the evanescent of gradient thickness is relative all very little, the increase of key groove has significantly improved the productibility of resulting device.By Fig. 9 and Figure 10 as seen, when the free space optical beam diameter is reduced to 200 μ m when following, the tolerance of required key groove begins to improve.The free space beam size is reduced to 100 μ m when following, can obtain more benefit.

Though the discussion of front is pointed out, owing to multiple reason, reduces the manufacturability that beam sizes can significantly improve device, the size of prism coupler (and any input optical device before) and layout restrictions the minimum beam size compatible with this layout.Small diameter optical beam is dispersed in less relatively propagation distance fast.This distance quality factor commonly used is called rayleigh range and (is expressed as z herein _R), and by relation

Definition, wherein n is the refractive index of the medium that passes of beam propagation, and other symbols are identical with the definition of front.Physically, rayleigh range roughly keeps the distance of collimation corresponding to light beam.When use prism structure with light when external light source is transferred to waveguide, in order to obtain high coupling efficiency, beam waist must be positioned at input beam near the projection on prism-coupled surface.Before intersecting with the prism-coupled surface, light beam must (usually in air or other input optical device) be propagated certain distance in the silicon prism coupler.If beam sizes is too little, the path that allows in air, input optical device and the silicon will be too little, so that can't realize in the reality.Next will describe an example calculations in detail according to the context of the structure of the equipment among Fig. 1.

If the size of foundation base of the prism structure shown in Fig. 1 is 0.45mm (edge, corner that produces along the darkest part of horizontal amount of v-depression to etching processing), and wavelength is that the light of 1550nm is from the θ of silicon prism coupler with 45.5 ° _SiThe value emission must be propagated the path of about 400 μ m from importing prism facets to the corner light beam of prism structure and prism-coupled coupled surface.Must be included in prior to the transmitting range of prism facets in the calculating of position of beam waist.This transmitting range comprises the aerial path of light beam, and is used for the thickness of optical element of pre-service light beam.According to the number of required element, prior to the scope of the beam path of input face at 1mm (the reasonable manufacturing tolerance that device is aimed at) in number mm scopes.Because the refractive index of air (more at large, the refractive index of input optical device) more much lower than the refractive index of silicon, and the path prior to prism facets has surpassed the path in the prism structure usually, and rayleigh range is calculated mainly by the emission decision prior to the input prism facets.The z that utilization provides above _RRelation can draw, for the beam diameter of 20 μ m, airborne rayleigh range is 0.2mm, then is 0.7mm in the silicon.For 63 bigger μ m beam diameters, airborne rayleigh range is about 2.1mm, then is 7.3mm in the silicon.For the beam diameter of 100 μ m, airborne Rayleigh path is about 5.1mm, then is 17.6mm in the silicon.In order in air, to obtain transmission range to several millimeters magnitudes, calculate demonstration, using size is feasible at the light beam of 60-100 μ m magnitude.

Because the thickness as polarization beam splitter, ripple plate and typical micro optical elements such as little wedge surface or prism can reach 0.5mm or littler, can use the light beam after some elements come shaping, control collimation lens, and adjust the polarization direction of light beam.Therefore, the beam sizes of 60-100 μ m meets the requirement of penlight, miniaturization assembly and micro optical element input row.For simplifying the problem of packing and other assembling previously discussed aspects, select the scope of design of the input beam diameter of 60-100 μ m magnitude to be fit to.

Last consideration about the input beam size is, the input beam size is the lower limit of the beam sizes that applies of prism coupler, evanescent and waveguide.The character of these three elements has determined the angle of prism inner light beam, θ _Si, thereby directly influence the projection of light beam on the prism-coupled surface, (see figure 2).In addition, the material of prism coupler and geometric configuration will be according to relational expressions How the decision light beam reflects on the input prism facets.It is pointed out that usually, because the refraction at place, inclined-plane and the projection of coupling surface surface,

Be defined as the beam diameter in the free space).In typical case, light beam is in the lip-deep projection of prism-coupled

Surpass one to three times of free space optical beam diameter.

Figure 11 has shown in different device layer thickness among Fig. 1 and the full telecommunication wavelength coverage, the amplification of the lip-deep light beam of prism-coupled that these influences cause.As can be seen, in most cases, light beam has amplified 1.6-2.0 doubly along propagation axis.Bigger value and increasing faster (as for θ _Pr=54.74 °, W=1.0 μ m) corresponding to the increase of refraction effect during high incident oblique angle on the prism inclined-plane.Because same reason, from the angle of assembling, these structures are not very suitable.Therefore, from fact considering, the relative free space value of beam sizes of supposing the prism-coupled surface has been increased 1.4-2.4 doubly.Equally, note that by selecting specific duct thickness and prism angle (as W=1.7 μ m, θ _Pr=54.74 °), the projection of input beam on coupled surface can be substantially and Wavelength-independent.Like this, all can obtain suitable small beam size for any wavelength in the wavelength coverage, thereby simplify Design of device.This makes given prism wafer/evanescent/waveguide arrangement disposing high coupling efficiency ground use under the wide wavelength coverage that manys than random device.

Need be appreciated that,, can produce, transmit and regulate light signal by the multiple different element of design and installation in order to obtain the required beam characteristics among the present invention.Ensuing explanation comprises the typical construction of a plurality of light sources and optical element row, these structures can for Fig. 1 in similar device an interface easily is provided.

In addition, more corresponding application can be selected the interface of the characteristic of prism coupler, evanescent and waveguide with simplification and external light source or receiving element.Especially, some elements that are used for transmitting and regulate input optical signal can design at prism coupler wafer or chip internal, thereby have reduced the sum of independent component and simplified assembling process.By material, thickness and the geometric configuration of selecting suitable evanescent and waveguide, can obtain favourable emission geometric condition and beam shape, equally also simplified assembling process.

Laser diode is to use the exemplary light sources of using always in the electrooptical device of telecommunication wavelength (1.1-1.65 μ m).A lot of infra-red laser diodes generally include the sandwich construction of a GaAs based or indium phosphide material, and light is from the cleavage limit surface launching (the technical limit emission laser diode that is called) of laser chip.This laser diode can directly use with the form of this chip, and perhaps, in the encapsulation technology of having set up in the multiple prior art, this laser chip can be connected to an output optical fibre by a series of optical elements.The laser diode of second quasi-representative is called the vertical cavity surface emitting laser in technology, or VCSEL.Infrared VCSEL comprises a sandwich construction (using gallium arsenide, indium phosphide or InGaN arsyl material), and wherein, light is launched perpendicular to layer heap and through the topsheet surface of device.

For some application, need to use the Free Space Optics device to be sent to the prism structure from laser chip.Direct and laser coupled can realize very compact encapsulation, and the Polarization Control of height is provided.Yet infrared wavelength is longer because the surface of emission of laser is very little, and output beam may seriously be dispersed.Be operated on direction, have an appointment usually 32 °-50 ° FWHM beam divergence of limit emission laser diode in the 1300-1600nm scope, and be parallel to 10 °-25 ° the FWHM beam divergence of having an appointment on the direction of knot perpendicular to knot.

Because beam divergence is very big and anisotropy, need two lens to realize effective free space beam collimation of high wavefront quality at least.In a kind of lenticular unit, used the cylindrical lens of pair of cross to proofread and correct astigmatism, and the collimation on fast axle and the slow axis is provided.Highly disperse or " soon " axle for effective collimation, first cylindrical lens is made (" GRIN " lens of technical being called) by a kind of material of graded index usually.Collimate less disperse or " slowly " axle second cylindrical lens can make with multiple optically transparent material because the lens moulding itself is not enough to provide collimation.After connect the input beam of outgoing in the typical laser diode of miniature GRIN rod lens diameter can select to drop on 40 μ m in the scope of several mm.In the configuration, the angle of divergence that first lens are used to reduce perpendicular to the knot direction equals to be parallel to the angle of divergence of tying direction up to its value in second, makes the circular and correction astigmatism of light beam.This lens are sometimes referred to as " laser diode corrector " or " rounder ".Second lens can be traditional collimation microlens (being close to 0 so that beam divergence is reduced to) now, as plano-concave or aspheric mirror, and can be made by multiple optically transparent material.The advantage of configuration is in second, only needs one rather than two special lens.From after connect outgoing the typical laser diode of correcting lens the output beam diameter can select to drop on 100 μ m in the scope of 1mm.

The light beam that VCSEL emission appropriateness is dispersed, and the angle of divergence covers 29 ° (for lens-type parts) to 18 ° scopes.The lens that use can be traditional collimation microlens (being close to 0 in order to beam divergence is reduced to), for example plano-concave or aspheric mirror, and can make by multiple optically transparent material.For obtaining the collimated light beam of penlight diameter, can introduce the part of integrated microprism as vcsel structure self.So, for the VCSEL useful area of 3 μ m, can obtain the collimated light beam that diameter is 100-200 μ m.Though the VCSEL of middle infrared wavelength (1270-1650 μ m) has just begun to occur, they are having potential advantage aspect component number that reduces photoelectric subassembly and the complexity.

In other were used, one section optical fiber can be used as the conduit that light is delivered to prism coupler from LASER Light Source.If LASER Light Source is positioned at the independent cover that has optical fiber output, the waveguide assembly of prism-coupled must have the input optical fibre parts that can directly link to each other with the output of LASER Light Source.(if a plurality of fiber devices are arranged between the waveguide assembly of LASER Light Source and prism-coupled, and then the input optical fibre parts of the waveguide assembly of prism-coupled must link to each other with the terminal optical fiber output of link).If LASER Light Source is introduced in the identical assembly as the prism-coupled waveguide assembly, use for some, between laser chip and prism coupler, use staggered optical fiber still very favourable.For example, use the optical fiber of the different termination of a Gent, the collimated light beam size and dimension that the scope that can realize is wideer.This special termination can be applicable on an end of the nearest optical fiber of prism coupler, and generally includes optical fiber one end shaping, or a microprism directly is fused on this end of optical fiber.The size and the radius of the sweep by changing optical fiber connector or lens are at the collimated light beam that can obtain a branch of minimum spot size (also making " beam waist ") on user's operating distance.Use present technology, can make the optical fiber collimator of beam waist diameter in 15 μ m to 100 mu m ranges after this manner.LASER Light Source can use the lenticular unit of introducing in detail in the prior art to link to each other with the other end of optical fiber.Therefore, for Figure 13,14 and 15 configuration, can produce diameter from lens/optical fiber component of fusion for optical fiber and laser input be 60 light beam.

Though lenticular unit provides necessary beam collimation, need still to guarantee that light beam is in suitable polarization state before entering prism.Though transverse electric (TE) and transverse magnetic (TM) polarization state can be coupled into waveguide efficiently, at specific θ _SiUnder the value, only a kind of polarization state can be coupled efficiently.Because the stable and known light beam of limit emission laser diode emission polarization state can use a microwave board that polarization state is rotated to suitable attitude.Use for some, can launch consistent suitable polarization attitude by selection and from edge-emitting diode, thereby omit the ripple plate fully.If input beam passes from a polarization-maintaining fiber, can when assembling spin fiber guaranteeing obtaining suitable polarization state, thereby do not need extra polarization optics device equally.

Yet the polarization state of VCSEL is also imprecise known.Especially, polarization state may not change in time, but direction the unknown is perhaps opposite, polarization state may be in time or laser drive current change.Similarly, if used the input optical fibre of unpolarized maintenance, polarization state of light is with uncertain and can drift about in time.A kind of element of the optics circulator that is used for prior art is also available in the present invention to obtain correct polarization state, as shown in figure 12.Input beam is transferred to the birefringence element 50 that single input beam can be separated into two bundle light beams: a branch of polarization state that is in requirement, the polarization state of another bundle is vertical with the polarization state of requirement.Because the refractive index of light is for two kinds of polarization state differences, two-beam is propagated in device 50 with different directions at the very start.The light beam that is in the polarization state of requirement continues to propagate in the medium that does not influence its polarization state.Yet the polarization state light beam vertical with the polarization state of requirement passed second birefringence element, is about to its polarization state and revolves the beam direction control element 52 that turn 90 degrees to the polarization state that requires.Last output is two to restraint independently light beam, is slightly offset mutually, and all is in required polarization state.In most the application, two elements 50 and 52 combine, and form one and are easy to the optics subassembly proofreading and correct and make.Natural birefringence material (YvO for example ₄, quartzy, rutile or lithium niobate) or synthetic birefringence element (as follows wavelength diffractive) all can use.If the direction of polarization member makes two-beam be radiated on the prism facets 14 with identical incident angle, two-beam can be coupled into ducting layer 12 efficiently.For some application, after light beam enters ducting layer, can combine them again.Suitable guide frame by SOI ducting layer 12 self inside is easy to finish and repeats to close.In case input beam is collimated and obtained required polarization state, if the light of required wavelength is coupled into waveguide efficiently, light signal must be launched from prism facets with suitable incident angle.For as the embodiment among Fig. 1, light beam can be directly with θ _AirAngle emission enters prism structure, perhaps, can use little optical element that input beam heavily is directed to input angle θ on the prism structure _AirBecause the encapsulation aspect for edge-emitting diode light source, optical fiber input or vertical cavity surface emitting laser (VCSELS), is launched more convenient usually (θ when directly launching with parallel light in wafer _Air=-35.3 °).For external light source,, be suitable for equally perpendicular to waveguide emission (θ when directly launching as VCSEL _Air=54.74 °).As seen from Figure 4, by being that given wavelength is selected suitable duct thickness, can select suitable launching condition.Yet for some design proposals, the required duct thickness in particular transmission angle may be incompatible with competition device demand.Because these reasons, be suitable for some beam direction control optical device are encapsulated near the light source.Except that angle Selection, beam direction control optical device can use together with other collimation techniques (as the location of the relative prism of light source), with guarantee light beam properly (translation) be positioned on the prism.

Figure 13 and Figure 15 have provided in detail with the typical method of light beam from edge-emitting diode or fiber guides to prism facets.Among Figure 14 and Figure 15, be directed to a micro-optic prism or the angle of wedge from the collimation free space beam of an edge-emitting diode or optical fiber.The amplitude of beam deflection is along with the increase of the refractive index of micro-optical device and wedge angle and increase.Can use a similar micro-optical device that output beam is directed to one at output terminal and receive optical fiber.Perhaps, diffraction optical element such as linear phase grating can be used as beam direction control element.Diffraction optical element is very effective in beam direction control is used, and reason is that the peptizaiton of the grating of good design can be very big, makes that polarization angle can very big (can reach 60 °).Another advantage is that complicated diffraction optical element can be realized more than a kind of optical function simultaneously, provides more performance with less elements.As an example, except as the beam direction control element, diffraction optical element can be used for wavefront correction to improve the wavefront quality.

Among Figure 13, be used for light is reflexed to suitable incident angle θ with the micro-reflector 54 of microelectromechanical systems (MEMS) disposal route manufacturing _AirIn the example shown in Figure 13, this catoptron is fixed on correct angle and position with little hinge 56 of silicon micro-processing method manufacturing.Use a benefit of this technology to be, the position of micro-reflector 54 and angle can be handled and regulate, and make θ _AirThe position of the corner of relative etching with light beam can be adjusted, so that the light that the transmission guided wave is led is the strongest.With previous the same, same structure also is used in outgoing side, and output beam is directed to reception optical fiber.

Figure 14-19 shows the concrete input and output optical arrangement that can be connected with the waveguide assembly of prism-coupled with high coupling efficiency.Though special optical element (for example lens-type optical fiber 60 among Figure 15) only can draw in one embodiment, can infer that a given element can be applied among the multiple different embodiment easily.Therefore, the embodiment that draws in detail among Figure 14-19 in fact only is example, and does not provide possible configuration in detail.

Figure 14 and 15 has shown that optical fiber traditional in two draws photoelectric subassembly configuration, and these photoelectric subassemblys are connected to the waveguide assembly of prism-coupled.Form parts though prism structure and SOI device wafer couple together, the encapsulation of input and output optical device row can comprise independent parts.In this case, optical element is positioned in the bearing on the independent carriage and proofreaies and correct, and this carriage is connected with prism/SOI device waveguide elements again and proofreaies and correct.Perhaps, if prism structure is produced on the silicon wafer, can use extra mask and etching processing to define groove, this groove is installed in the free space element in the surface that faces the silicon wafer that connects the surface.In two kinds of situations, size is substantially equal to the groove processing of external dimensions of optical element in backing material.Then, free space optical elements is positioned, calibrates and be fixed on the assigned address in the groove.Among Figure 14 and Figure 15, light signal is introduced assembly and is therefrom drawn (technical being called " optical fiber of magnetic tape trailer fibre ") by an optical fiber.

Among Figure 14, two important autonomous devices are arranged in the photoelectric subassembly of magnetic tape trailer optical fiber.Input optical fibre interface and output optical fibre interface are respectively at a side and the opposite side of this assembly.Use polarization-maintaining fiber 70 among the embodiment shown in Figure 14, guaranteed to obtain not have the correct polarization state of other spuious polarizations like this.Micro-optics lens (are equivalent to a micro-spherical surface, a miniature grin lens, or micro-spherical surface lens) be used to collimate the diverging light that from optical fiber, comes out, subsequently the collimation after light beam be directed to beam direction control element 74, thereby this element make the beam deflection certain angle on the plane of incidence 76 of prism 78 with suitable incident angle θ _AirIncident.If beam-control element 74 further is positioned on the independent sub-bearing, and anglec of rotation degree that can be as shown in figure 14, then incident angle just can adjust when assembling, and constant at equipment operating period internal fixation.At the output terminal of equipment, output beam passes the optical element of same sequence with opposite order.Though equipment output end is not necessarily to need polarization-maintaining fiber, use polarization-maintaining fiber to make the structure among Figure 14 can be used as bilateral system.

Similar among embodiment among Figure 15 and Figure 14, showed an output port and input port the equipment that assembles in the same side.When the overall dimensions of assembly need keep very little, the structure of this uniqueness was very favourable.As shown in figure 15, direction of beam propagation is positioned at the reversed by reflective optical elements in the SOI wafer ducting layer.Light signal is introduced by the optical fiber 80 that is positioned at the assembly bottom.In this structure, a micro lens 82 directly fuses together with optical fiber 80, so just utilizes single subassembly to obtain the light beam of well collimated.Because light beam is not clear from lens-type optical fiber outgoing rear polarizer attitude, polarization control component 84 is used to convert incident beam to light beam that two bundles have required polarization state.The direction of polarization control component 84 makes two to restraint emergent light horizontal displacements (plane that promptly comprises this two light beams is parallel with wafer plane).Because the spacing of this two-beam is less, get magnitude at hundreds of microns, so two-beam can come deflection with same beam direction control element 86.Two-beam is with identical angle θ _AirTransfer to the plane of incidence 88 of prism 89, and be coupled into the ducting layer 12 of SOI wafer.This two bundle exists the light of phase shift to be combined into a single beam again by the optical element that is positioned at ducting layer subsequently each other.Pass in the SOI ducting layer behind remaining photoconductive structure, emergent light is from the outgoing of output prism face, and spreads into similar optics output row.Yet unless need obtain a unpolarized output beam again, the polarization control component on the output terminal can be omitted.

Figure 16 has showed an alternative real part.Wherein, one group of LASER Light Source 90 directly is integrated in the assembly.Because VCSEL launches light by outside surface, and size can less (about 100-250 μ m), and they can be lined up with a rectangular silicon prism 94 of etching in silicon wafer or the wafer die easily.As shown in figure 16, the control of beam collimation and beam direction can realize by refractor 92 arrays and diffraction lens or beam-control element.The size of component scope does not wait from several microns to several millimeters in the lens combination.Most of compact structure can by directly in VCSEL wafer self etching control prism and/or collimation lens realize.All light beams are all with identical angle θ like this _AirTransfer to a prism group 94, be coupled into waveguide 12 subsequently, and from output face 95 outgoing of prism bar 94.On the receiving terminal array that one group of similar lens and diffraction element 96 are used to make beam deflection, shaping and assemble leaded light fibre 98.Perhaps, also can use edge-emitting diode in the similar structures, as shown in figure 17, as long as the spacing of array is large enough to hold big slightly limit emitter.With reference to Figure 17, a kind of embodiment of limit emission laser diode 91 that utilized has further utilized a laser diode collimator lens array 93, and being placed in the output terminal of limit emission laser diode array 91, this place's collimator lens array is used to beam direction control element 92 that a suitable signal distributions is provided.Figure 18 has shown the another kind of version of embodiment among Figure 17, and has the lens-type fiber array 97 of the output terminal that is placed in collimator lens array 93.

Reduce the total number and the set-up procedure of element if desired, can in silicon prism wafer or mould, process required optical element, as shown in figure 19.In this structure, light beam enters silicon prism wafer 100 by any specific in the surface of user's prism wafer 100, rather than directly with suitable angle θ _AirIncident beam is transferred to etched " hypotenuse " prism input face.In the example of Figure 19, light beam enters by the surface 102 of prism wafer 100, and this surface faces the surface 104 (prism-coupled surface) that is connected with SOI wafer 106.When light beam was propagated in prism wafer 100, it can run into the surface of its direction of propagation of a series of changes, the required emission angle in obtaining silicon, θ _SiThese surfaces can be by the topsheet surface 102 of wafer 100 and lower surface 104 or the surface composition that forms of other etch processes arbitrarily.For a branch of light beam of in silicon wafer, propagating,, in very wide ranges of incidence angles, all can on these surfaces, obtain total internal reflection because the refractive index of silicon is very high.For air-silicon interface (supposition air refraction n ≈ 1, silicon refractive index n ≈ 3.5), required incident angle must be greater than 16.6 ° of the critical angles of total internal reflection, and for a silicon-silicon nitride interface (supposition silicon nitride refractive index n ≈ 2), required incident angle must be greater than 34.8 °.If incident angle less than critical angle, by gold-plated as catoptron in the part 108 on surface 102, still can obtain very high reflectivity.Because the thickness of silicon wafer is less relatively, be about 500-700 μ m, when light beam is propagated one section shorter relatively physical distance (several millimeters approximately) in silicon wafer 100, still can run into many different reflecting surfaces.Therefore, silicon prism wafer itself can be used as the low-loss beam direction control element use of a compactness.

In the simplest structure, prism wafer is used for (1) with beam direction to a suitable angle θ _Si, and (2) coupled light beam enters waveguide.After the topsheet surface emission of passing the silicon prism coupler entered, light beam reflected and is incident to etching surface in silicon wafer.If incident angle is enough big on the etching surface, the meeting experiences total internal reflection is gone up on this surface like this.On the contrary, enough little incident angle causes total reflection light to be launched towards topsheet surface.When incident angle was enough big on the topsheet surface, light beam can be in topsheet surface experiences total internal reflection once more.After the topsheet surface experiences total internal reflection, light beam is with suitable emission angle theta _SiTowards the emission of optical coupled zone.The method of this control bundle is very effective, because can enter the wideer emission angle theta of optical coupled zone acquisition than directly directly launching from silicon prism coupler top like this _Si(because high index of refraction of silicon).By adding optical element on the topsheet surface in the direct path of light beam, can increase some additional optical functions.In the example of Figure 19, optical element can be positioned at the primary entry point that light beam enters silicon prism coupler topsheet surface, or the point of the total internal reflection on the topsheet surface.These optical elements can include, but are not limited to following element: be used for collimating refraction or the diffraction lens of dispersing input beam, or other provide the diffraction optical element of additional beam direction control, beam-shaping, wavefront correction or Polarization Control ability.

Use these refractions and diffraction element that additional optical function is provided, for example will be integrated in collimation and Polarization Control in the silicon prism coupler.Utilize the combination of technology such as traditional lithography, photoresist flow, plasma etching, diffusion and injection to process micro lens at silicon.Perhaps, the gray scale lithography technique can be used to produce more complicated aspheric lens shape.Utilize traditional lithography technique can in silicon substrate, process many diffraction elements, i.e. optical grating construction.Yet, may need more high-resolution lithography technique (as electron lithography) to obtain can be used as the sub-wavelength grating structure of polarization control component.

How to influence equipment performance by thinking over beam shape, the coupling efficiency of the exemplary apparatus among Fig. 1 can obtain significant raising.Here have three main interfaces to need to consider: (1) is from the shape of the free space input beam of input optical device; (2) the definite form of evanescent; And the shape of (3) free space output beam and output reception optical device.

Usually, coupling efficiency can be determined with the overlap integral of knowing from prior art.From then on integration can draw, and only could obtain 100% coupling efficiency when input beam and output beam form fit.

For the exemplary embodiments among Fig. 1, need to consider three relevant overlap integrals:

(1) η ₁The beam shape of=light source is with respect to light beam projecting required on the prism-coupled coupled surface

(2) η ₂The lip-deep beam shape of=input prism-coupled is with respect to the light beam that transmits from the output prism coupled surface

(3) η ₃The shape of=the light beam that transmits from the output prism coupled surface receives the required beam shape of optical device with respect to output.

Here at first coupling efficiency is discussed according to the context of the first-selected embodiment that shows among Figure 20.Thus embodiment as seen, input and output silicon prism is separated by the evanescent of constant thickness and constant refractive index with the silicon waveguide.

For the laser input and the optical fiber output of index zone tail optical fiber optical fiber, the total coupling efficiency of the embodiment among Figure 20 is defined as:

η＝η ₁η ₂η ₃≈64％

Coupling efficiency η ₁By the loss that Gaussian beam caused decision from light source such as optical fiber or a branch of well collimated of laser input generation.If optical device is integrated in the light source lens-type optical fiber or the LASER Light Source of collimation and beam-shaping device (for example used integrated), η ₁To be very high, near 100%.Coupling efficiency η ₂Ratio by the power of the power of the free space output beam of prism and free space input beam is determined.Yet, to Gauss's input beam of free space, η ₂Can not surpass 80%.Known from prior art, since the mode intensity difference of this embodiment input and output light beam, η ₂Be restricted.Input beam is a Gaussian along the intensity of the direction of propagation, and from the light beam of output prism along the intensity distributions of the direction of propagation for be exponential type (referring to Figure 20 (b) and (c) amplitude with respect to the curve of position).At last, because identical reason is coupled to output optical efficiency η ₃Be about 80%.Equally, this is because from incomplete overlapping the causing of the required Gaussian-shaped beam of the exponential envelope free space beam of prism outgoing and fiber-optic output.Thereby,

η=η ₁η ₂η ₃≈ (1) * (0.8) * (0.8)=0.64 or the approximately insertion loss of 2dB.

Clearly, if improve the coupling efficiency of embodiment shown in Figure 20, need make further beam shaping with η ₂Or η ₃Bring up to more than 80%.For a light source, as laser, modal beam shape is that Gaussian or square wave type distribute.The coupling efficiency that can prove these two kinds of waveform generation all is η ₂=80%.Improve η ₂, clearly necessarily require input beam to have and the close intensity distributions of exponential envelope from the light beam of output prism outgoing.Realize above intention, a kind of method is to use a kind of " half Gauss " imports waveform.As shown in figure 21, the initial input Gaussian beam incides on the splitter structure 120, and aligns with the intersection point on channel-splitting filter surface in the Gaussian beam center.Such two bundles, half light beam is transferred to prism (not shown) respectively and is coupled to waveguide.Can use suitable optical element (as a refrative mirror 122) that wherein a branch of half light beam is reversed.Guarantee that this two bundles, half light beam is compound no longer again very important before entering waveguide, otherwise can cause the interference fringe of strong modulation input beam intensity distributions.In this case, η ₂The overlap integral of=half Gaussian waveform and output index waveform=97%.Convert to two the bundle half Gaussian beam process in can reduce coupling efficiency η ₁Clearly, any significant advantage is arranged, η will be arranged if regulate the incident beam waveform ₁＞83%.Because the standard method meeting of the light beam of Gaussian significantly reduces intensity, coupling efficiency η to be used for distributing more from one of input beam generation ₃To be more difficult.To structure shown in Figure 20, can expect that if additional incident beam shaping is arranged maximum total coupling efficiency η can reach 80%; If be not added into the irradiating light beam shaping, then can only reach about 64%.

Can obtain total coupling efficiency η higher and easier realization among the embodiment shown in Figure 22.In this embodiment, silicon prism and silicon waveguide are separated with the evanescent that position linearity changes by a thickness.On input face, the thickness of the evanescent when energy at first transfers to ducting layer is less than the evanescent layer thickness of most of energy when all being transferred to ducting layer.In output face, when most of energy was still in waveguide, the one-tenth-value thickness 1/10 of evanescent was bigger.And when ducting layer is coupled out and enter prism, can reduce when the energy of light beam.Because can keep the approximate Gaussian beam shape the whole optical path from incident light source to outgoing optical fiber interface, this mode can obtain the coupling efficiency higher than embodiment shown in Figure 20.

As previously mentioned, from a branch of standard incident beam of LASER Light Source or optical fiber for having high coupling efficiency η ₁The collimation Gaussian beam.Improve coupling efficiency η ₂, must be more near Gaussian beam from the free space output light-wave shape of prism outgoing.Although output light is not real Gaussian beam usually, if newly export light and the overlap integral of the overlap integral of importing Gaussian beam greater than exponential envelope and input Gaussian beam, coupling efficiency still can surpass 80%.Known from technical literature, a kind of make output beam more the method for Gaussization be to allow evanescent layer thickness gradually change with direction of beam propagation.If evanescent layer thickness is constant, then light beam have a few from waveguide, to be coupled out and enter prism with identical stiffness of coupling, the result is that the output beam waveform can be written as g (z) ∝ exp (α z) (seeing Figure 20).Stiffness of coupling increases with evanescent layer thickness and reduces, and reduces and increase with evanescent layer thickness.If the output beam waveform is more near the input beam waveform, at first will be very weak from the coupling of the light of prism surface outgoing, so most of light is still stayed in the ducting layer.For guaranteeing this point, evanescent must fully be higher than the optimum coupling value.For realizing this point, the stiffness of coupling of light must increase, thereby most of light can be drawn, and forms the peak of output " Gauss " light beam.Therefore, this part light must be as quantizing the interface of evanescent near the optimum thickness place.Like this, most of energy sends out from waveguide, and passes output prism fully from system's outgoing.Though stiffness of coupling continues with the reducing and increase of evanescent layer thickness,, begin to reduce from the amount of the light of prism outgoing because the energy of light constantly descends in the ducting layer.Can obtain more to meet the output light-wave shape of Gaussian distribution like this.Though output beam is not real Gaussian waveform usually, new output beam and the overlap integral η that imports Gaussian beam ₂≈ 97%.Importantly, the gradient of evanescent is necessary for suitable value, to produce required beam shape.This gradient fixes on the part of front beam sizes really and discusses.

Because the free space output beam from prism has the required Gaussian waveform of output optical fibre interface, coupling efficiency η ₃Now can be very high.As previously mentioned, from the approximate Gaussian light beam of output prism outgoing and overlap integral η as the gaussian model of optical fiber feature ₃Can be up to 97%.If needed, can use to those and be used for the laser diode light beam being done to the optical fiber cable the similar collimation and the sphering optical device of optical device of shaping, reduce any output beam and disperse or ovality in light transmission.Be used at last collimated beam to the lens of optical fiber are always needed.These lens can be lens-type optical fiber or collimating apparatus parts part of the whole, also can be for this purpose to cooperate an ordinary optic fibre terminal to use an independent spherical lens or gradient-index lens.

Total coupling efficiency of embodiment shown in Figure 22 can be expressed as:

η=η ₁η ₂η ₃≈ (1) * (0.97) * (0.97) ≈ 0.94, or the approximately loss of 0.3dB.This may be to obtain from laser instrument or based on the simplest method of the efficient end-to-end coupling that is input to optical fiber output of optical fiber, and this technology can be used for inserting other more responsive application of loss.Yet the raising of coupling efficiency must be weighed the additional demand of the required gray scale lithography technique of the evanescent that obtains variation in thickness.It should be noted that and anyly can produce a similar approximate Gaussian type output beam or more can obtain 〉=94% high coupling efficiency from output prism near the evanescent structure of the output beam of Gaussian.That is to say that the raising of coupling efficiency is not limited to the evanescent of thickness linear change.For purpose of the present invention, " more near Gaussian " may be defined as the output beam waveform that can improve the known heavy iterated integral arbitrarily.For example, can prove that a thickness is along with producing a branch of more near the light beam of Gaussian than the evanescent of thickness linear change along the evanescent that changes apart from logarithm of waveguide.(coupling efficiency that draws on logarithmic coordinate will obtain a more symmetrical coupling efficiency peak or a curve with the curve that bed thickness changes).It is more complicated usually to make such thickness structure, if but total coupling efficiency of 94% is not enough to satisfy the insertion loss demand of application, and it is essential that such structure is still.

Claims (46)

1. optical couping device that the path of introducing the silicon optical waveguide and drawing from the silicon optical waveguide is provided for signal, this silicon waveguide is formed in the superficial layer of silicon-on-insulator (SOI) wafer, this wafer comprises a silicon optical waveguide layers on the insulation course that is formed on the silicon substrate, and this optical couping device comprises

A silica-based prism coupler that is used for blocking from the input beam of light source, this silica-based prism coupler is permanently affixed on this SOI wafer, and make that a first surface of this prism coupler is substantially parallel and continuous with the flat surface of this SOI wafer, the refractive index of this silica-based prism coupler is equal to or greater than the refractive index of this silicon optical waveguide;

Be inserted in the free space micro-optic input element between light source and the silica-based prism coupler, be used for beam collimation, shaping, and with the specific entrance and the incident angle of the silica-based prism coupler of beam direction;

An evanescent wave coupling regime that is arranged between this silica-based prism coupler and this silicon optical waveguide; And

Be placed on the free space micro optical element in the path of the light beam of the output surface outgoing of silica-based prism coupler, be used for beam shaping, collimation or convergence, and with receiving element of beam direction.

2. the optical coupled apparatus of claim 1, wherein, this device also comprises a light source with the coupling of free space micro-optic input element.

3. the optical couping device of claim 2, wherein, the wavelength of light source drops in the 1.1-1.65 mu m range.

4. the optical couping device of claim 2, wherein, the output beam of light source is essentially monotype.

5. the optical couping device of claim 2, wherein, whole intensity of light source drop on basically centre wavelength ± the 5nm scope in.

6. the optical couping device of claim 2, wherein, light source is a limit emission laser diode.

7. the optical couping device of claim 5, wherein, micro-optic free space input element behind the emission laser diode of limit comprises one first micro optical element, this first micro optical element will be decreased to the magnitude of the angle of divergence of the output beam that is parallel to knot perpendicular to the angle of divergence of the output beam of tying, proofread and correct astigmatism, and produce a circular light beam and one subsequently with second micro optical element of beam collimation.

8. the optical couping device of claim 6, wherein, micro-optic free space input element behind the emission laser diode of limit comprises the second microtrabeculae face lens of graded index microtrabeculae face lens that will collimate perpendicular to the output beam of knot and an output beam collimation that will be parallel to diode junction subsequently.

9. the optical couping device of claim 6, wherein, micro-optic free space input element behind the emission laser diode of limit comprises first spherical lens of a collimated light beam, be subsequently one with second spherical lens of beam convergence on the reception optical fiber components that is inserted between diode and the silica-based prism coupler.

10. the optical couping device of claim 6, wherein, micro-optic free space input element behind the emission laser diode of limit comprises first aspheric mirror of a collimated light beam, one second aspheric mirror subsequently with beam convergence on the reception optical fiber components that is inserted between diode and the silica-based prism coupler.

11. the optical couping device of claim 6, wherein, the micro-optic free space input element behind the emission laser diode of limit comprises a micro-optic ripple plate that is used for the rotatory polarization direction.

12. the optical couping device of claim 2, wherein, light source is a vertical cavity surface-emitting laser diode.

13. the optical couping device of claim 12, wherein, the micro-optic free space input element behind the vertical cavity surface-emitting laser diode comprises a micro-optic collimation lens.

14. the optical couping device of claim 13, wherein, the micro-optic collimation lens is a silicon lenticule.

15. the optical couping device of claim 12, wherein, the micro-optic free space input element behind the vertical cavity surface-emitting laser diode comprises a micro-optic ripple plate that is used for the rotatory polarization direction.

16. the optical couping device of claim 12, wherein, micro-optic free space input element behind the vertical cavity surface-emitting laser diode comprises an optical element, the incident beam that this optical element will be in the unknown polarizations attitude is converted into to have two of definite identical known polarization attitude and restraints independently output beam, and second light beam and first light beam are spaced from each other, but keep substantially parallel.

17. the optical couping device of claim 2, wherein, light source is an optical fiber.

18. the optical couping device of claim 17, wherein, optical fiber is monotype and supports random polarization state.

19. the optical couping device of claim 17, wherein, optical fiber is the monotype polarization-maintaining fiber.

20. the optical couping device of claim 17, wherein, the micro-optic free space input element behind the optical fiber comprises a micro-optic collimation lens.

21. the optical couping device of claim 20, wherein, the micro-optic collimation lens comprises fusion on optical fiber, forms a lens-type optical fiber.

22. the optical couping device of claim 21, wherein, from the diameter of the collimated light beam of lens-type optical fiber outgoing at the 10-110 mu m range.

23. the optical couping device of claim 17, wherein, micro-optic free space input element behind the optical fiber comprises an optical element, the incident beam that this optical element will be in the unknown polarizations attitude is converted into the independent output beam of two bundles with identical known polarization attitude, and second light beam and first light beam are spaced from each other, but keep substantially parallel.

24. the optical couping device of claim 1, wherein, micro-optic free space input element comprises the refraction angle of wedge that a high-index material is made, so that incident beam deflection.

25. the optical couping device of claim 1, wherein, micro-optic free space input element comprises a reflecting element, and this reflecting element can be moved and rotates by the electronics mechanism of actuating, and moves and angular deflection so that incident beam produces.

26. the optical couping device of claim 1, wherein, micro-optic free space input element comprises a diffraction optical element that makes incident beam angular deflection.

27. the optical couping device of claim 1, wherein, the thickness substantially constant of evanescent wave coupling regime.

28. the optical couping device of claim 1, wherein, the evanescent wave coupling regime has the thickness of wedge shape.

29. the optical couping device of claim 1, wherein, this device also comprises an optical receiver component that is used to receive from the output beam of free space micro-optic output element.

30. the optical couping device of claim 29, wherein, receiving element is an optical fiber.

31. the optical couping device of claim 29, wherein, receiving element is a lens-type optical fiber.

32. the optical couping device of claim 1, wherein, the input and output micro optical element, and covered anti-reflection coating on the input and output surface of silica-based prism coupler.

33. optical couping device that the path of introducing the silicon optical waveguide and drawing from the silicon optical waveguide is provided for signal, this silicon waveguide is formed in the superficial layer of silicon-on-insulator (SOI) wafer, this wafer comprises a silicon optical waveguide layers on the insulation course that is formed on the silicon substrate, and this optical couping device comprises

A silica-based prism coupler that is permanently affixed on this SOI wafer, and make that the first surface of this prism coupler is substantially parallel with the flat surface of this SOI wafer and be attached thereto that the refractive index of this silica-based prism coupler is equal to or greater than the refractive index of this silicon optical waveguide;

Form the optical element of the integrated component of this silica-based prism coupler, be used for input beam collimation, shaping, and with a specific entrance and the incident angle of beam direction to the silica-based prism coupler coupled surface;

An evanescent wave coupling regime that is arranged between this silica-based prism coupler and silica-based optical waveguide; And

Be placed on the free space micro-optic output element in the path of the light beam of the output surface outgoing of silica-based prism coupler, be used for beam shaping, collimation or convergence, and with receiving element of beam direction.

34. the optical couping device of claim 33, wherein, lenticule is formed in the connection surface of the surface of silica-based prism wafer rather than SOI wafer, so that the incident beam collimation.

35. the optical couping device of claim 33, wherein, diffraction optical element processing with the incident beam shaping, or disperses incident beam or angle deflects in the connection surface of the surface of silica-based prism wafer rather than SOI wafer.

36. the optical couping device of claim 33, wherein, have the angle surface anisotropy be etched in the silica-based prism coupler so that incident beam angle in whole internal reflection process deflects.

37. the optical couping device of claim 33, wherein, the sub-surface in the silica-based prism coupler has covered thin metal layer, and this metal level deflects the angle of incident beam as reflecting element.

38. the optical couping device of claim 33, wherein, enter waveguide at light beam from the silica-based prism coupler of importing the prism-coupled surface, and leave on the position of silica-based prism coupler that waveguide enters output prism coupled surface place, the evanescent wave coupling regime is wedge shape, like this, all to have be the intensity distributions of gaussian model to the light beam of being had a few in the outer optical couping device of SOI wafer waveguide substantially.

39. the optical couping device of claim 38, wherein, what use that the evanescent of wedge shape obtains is that the output beam of gaussian model intensity distributions makes light beam can be coupled to reception optical fiber efficiently substantially.

40. the optical couping device of claim 33, wherein, selected the thickness of the waveguide of certain SOI wafer, make that being parallel to light that wafer surface is launched and that be incident on the input prism facets from light source is reflected at a certain angle by silica-based prism coupler, this angle is relevant with the high coupling efficiency of specific wavelength.

41. the optical couping device of claim 33, wherein, selected the thickness of the waveguide of certain SOI wafer, make to be reflected at a certain angle by silica-based prism coupler perpendicular to the light wafer surface emission and that be incident on the input prism facets that this angle is relevant with the high coupling efficiency of specific wavelength from light source.

42. the optical couping device of claim 33, wherein, this device has also comprised a light source.

43. the optical couping device of claim 42, wherein, light source is the vertical cavity surface-emitting laser diode with suitable wavelength.

44. the optical couping device of claim 33, wherein, selected the thickness of the waveguide of certain SOI wafer, make and reflected by silica-based prism coupler from light light emitted and that be incident on the input prism facets, like this, light beam keeps constant substantially lip-deep being projected in of prism-coupled in the very wide wavelength coverage.

45. the optical couping device of claim 1, wherein, selected the thickness of the waveguide of certain SOI wafer, like this, for same wavelength, the evanescent wave coupling regime is made the thickness that coupling efficiency is optimized to setted wavelength and input beam size, has been substantially equal to form the quarter-wave thickness of the material of evanescent wave coupling regime.

46. the optical couping device of claim 45, wherein, the anti-reflection coating of evanescent and silica-based prism wafer can machine simultaneously with a treatment step.

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