CN114966980A

CN114966980A - Waveguide, optical component and integration method thereof

Info

Publication number: CN114966980A
Application number: CN202210493752.0A
Authority: CN
Inventors: 陈林
Original assignee: Shanghai Turing Intelligent Computing Quantum Technology Co Ltd
Current assignee: Shanghai Turing Intelligent Computing Quantum Technology Co Ltd
Priority date: 2022-05-07
Filing date: 2022-05-07
Publication date: 2022-08-30

Abstract

Embodiments of the present application relate to waveguides, optical assemblies, and methods of integrating the same. According to some embodiments of the present application, a first surface of a waveguide comprises, along a length of the waveguide: a first region having a first width; and a second region having a second width, wherein the second width is greater than the first width; wherein the waveguide is configured such that light can be transmitted to the second waveguide via evanescent coupling through at least a portion of the second region. Still other embodiments of the present application provide an optical assembly, comprising: a first device including a first waveguide, the first waveguide being the aforementioned waveguide; and a second device comprising a second waveguide, wherein the first device and the second device are coupled to a third region of the second surface of the second waveguide through at least a portion of the second region of the first surface of the first waveguide. The waveguide, the optical component and the integration method thereof can effectively solve the problems in the traditional technology.

Description

Waveguide, optical component and integration method thereof

Technical Field

Embodiments of the present application relate generally to the field of semiconductor technology, and more particularly, to waveguides, optical assemblies, and methods of integrating the same.

Background

The miniaturization, low cost, and the like of optical chips require the integration of components such as light sources, optical paths, detectors, and the like, and the low-loss integration of active devices and passive devices is also required to reduce the chip energy consumption, improve the chip performance, and the like by reducing the coupling loss. For the coupling of a laser and a passive waveguide chip (based on silicon or lithium niobate, etc.), the following methods are adopted at present: the independent laser chip is emitted from the end face, the emitting end face of the independent laser chip is coupled with the end face of the optical fiber by using a certain spot conversion structure, and laser is transmitted to the end face of the other end of the optical fiber along the optical fiber to be emitted and then enters the passive waveguide on the chip through the vertical optical fiber coupler on the chip; the laser is directly emitted from the end face, light beams are focused into a small mode spot through a lens and then are directly coupled into a passive waveguide of the chip, the end face of the waveguide can be provided with an end face coupler to reduce alignment requirements and coupling loss, an optical isolator is usually required to be arranged between the laser and the chip to prevent light from reflecting to enter the laser, or a certain inclination angle is arranged on the end face of the waveguide to avoid the original return of light. In both of these approaches, the resulting coupling loss is still large (typically greater than 5dB) and the integration level is not high. At present, a scheme in research stage is heterogeneous growth of laser, so-called heterogenetic integration, which prepares laser by heterogeneous growth of materials such as III-V group on materials such as silicon or silicon dioxide, but the technology is not mature at present due to problems such as lattice mismatch and thermal stress mismatch, the power of the obtained laser is generally lower (mW level), which is obviously lower than that of the III-V laser matched with the same lattice (hundred mW level), and the situation with higher power requirement is not suitable.

The present application thus proposes a waveguide, an optical component and a method of integrating the same.

Disclosure of Invention

An objective of the embodiments of the present invention is to provide a waveguide, an optical component and an integration method thereof, which can significantly improve optical coupling efficiency and product yield compared to the conventional methods and structures.

An embodiment of the present application provides a waveguide, the first surface of which comprises along the length of the waveguide: a first region having a first width; and a second region having a second width, wherein the second width is greater than the first width; wherein the waveguide is configured such that light can be transmitted to the second waveguide via evanescent coupling through at least a portion of the second region.

According to some embodiments of the application, wherein the second region comprises a graded region, a width of the graded region increasing along a length direction of the waveguide.

According to some embodiments of the application, wherein the second area comprises square areas of equal width.

According to some embodiments of the present application, wherein the first surface further comprises along a length of the waveguide: one or more sub-regions to the right of the second region; wherein the widths of the sub-regions are tapered along the length of the waveguide such that light can be transmitted from the one or more sub-regions to the second waveguide via evanescent coupling.

According to some embodiments of the application, the width of at least one of the sub-regions decreases linearly with increasing length of the waveguide along its length.

Another embodiment of the present application also provides an optical assembly, including: a first device comprising a first waveguide, the first waveguide being the aforementioned waveguide; and a second device comprising a second waveguide, wherein the first device and the second device are coupled to a third region of the second surface of the second waveguide through at least a portion of the second region of the first surface of the first waveguide.

According to some embodiments of the application, the third region comprises along a length direction of the waveguide: a fourth region having a fourth width, wherein the fourth width is commensurate with a width of at least a portion of the second region such that the first waveguide and the second waveguide can be disposed in alignment.

According to some embodiments of the application, the third region further comprises one or more second sub-regions to the left of the fourth region, wherein the width of the second sub-regions increases along the length direction of the waveguide.

According to some embodiments of the present application, the optical assembly further comprises a dielectric auxiliary layer located between the first device and the second device.

According to some embodiments of the application, the first device is an active device and the second device is a passive device.

According to some embodiments of the application, the first device comprises at least one of: a laser, an optical amplifier and a photodetector, wherein the first waveguide is an InGaAsP waveguide and the second waveguide is a lithium niobate waveguide, a silicon waveguide or an amorphous silicon waveguide.

Still another embodiment of the present application further provides a chip including the aforementioned optical assembly.

Another embodiment of the present application also provides an optical quantum integrated chip, which includes the aforementioned optical component.

Yet another embodiment of the present application also provides a method of optical component integration, comprising: respectively preparing a first device and a second device, wherein the first device comprises a first waveguide which is the waveguide, and the second device comprises a second waveguide; and bond coupling the first device and the second device such that light can be transmitted to the second waveguide via evanescent coupling through at least a portion of the second region of the first waveguide.

Still another embodiment of the present application further provides a method for optoelectronic heterogeneous integration, which includes the above method for device integration.

Compared with the prior art, the waveguide, the optical assembly and the integration method thereof provided by the embodiment of the application are expected to replace the traditional structure, the efficiency of the butt joint process can be improved, the alignment tolerance is large, the yield is high, and meanwhile, the optical coupling loss can be reduced.

Drawings

Drawings necessary for describing embodiments of the present application or the prior art will be briefly described below in order to describe the embodiments of the present application. It is to be understood that the drawings in the following description are only some of the embodiments of the present application. It will be apparent to those skilled in the art that other embodiments of the drawings can be obtained from the structures illustrated in these drawings without the need for inventive work.

Fig. 1-3 are schematic illustrations of a waveguide 100 according to some embodiments of the present application.

Fig. 4 and 5 are schematic structural views of optical assemblies according to some embodiments of the present application.

Fig. 6 and 7 are schematic structural diagrams of a second waveguide 200 according to some embodiments of the present application.

FIG. 8 is a schematic diagram of another optical assembly according to some embodiments of the present application.

Detailed Description

In order to better understand the spirit of the embodiments of the present application, the following further description is given in conjunction with some preferred embodiments of the present application.

Embodiments of the present application will be described in detail below. Throughout the specification, the same or similar components and components having the same or similar functions are denoted by like reference numerals. The embodiments described herein with respect to the figures are illustrative in nature, are diagrammatic in nature, and are used to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.

As used herein, the terms "substantially", "substantially" and "about" are used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the term can refer to a range of variation that is less than or equal to ± 10% of the stated numerical value, such as less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. For example, two numerical values are considered to be "substantially" identical if the difference between the two numerical values is less than or equal to ± 10% (e.g., less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%) of the mean of the values.

In this specification, unless specified or limited otherwise, relative terms such as: the terms "vertical," "lateral," "upper," "lower," and derivatives thereof (e.g., "upper surface," etc.) should be construed to refer to the orientation as then described in the discussion or as shown in the drawings. These relative terms are for convenience of description only and do not require that the present application be constructed or operated in a particular orientation.

Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and it is to be flexibly understood to include not only the values explicitly specified as the limits of the range, but also all the individual values or sub-ranges encompassed within that range as if each value and sub-range is explicitly specified.

Also, for convenience of description, "first," "second," etc. may be used herein to distinguish one element or group of elements from another. "first," "second," and the like are not intended to describe corresponding components.

The waveguide 100 proposed in the present application has a first surface comprising, along a length direction of the waveguide (as indicated by arrow a in fig. 1): a first region 101 having a first width; and a second region 102 having a second width, wherein the second width is greater than the first width; the waveguide 100 is configured such that light can be transmitted to the second waveguide 200 via evanescent coupling through at least a portion 108 of the second region 102.

The waveguide provided by the application can be used for carrying out optical coupling propagation with the waveguide positioned above or below the waveguide, and can obtain larger alignment tolerance in an actual process through the wider second region, so that the product yield in an alignment integration process is favorably improved.

According to some embodiments of the present disclosure, as shown in fig. 2, the second region 102 may include a tapered region 103, and a width of the tapered region 103 increases along a length direction a of the waveguide 100 to generate an adiabatic tapered structure, which may adiabatically increase a width of a typical single-mode or few-mode waveguide from a micrometer level to a large value, for example, the tapered region may increase linearly along the length direction of the waveguide with an increase in the length thereof, and the difficulty of coupling alignment is reduced by the wide region, thereby improving the yield of the product. A structure in which the waveguide width linearly decreases or increases with increasing length is referred to herein as a taper structure, for example, the taper region between a and B in fig. 2 is a taper structure, and when the width of the taper region 103 linearly increases with length, it may also be referred to as a "taper waveguide segment".

The second region 102 may also include a region 104 of constant width along the length of the waveguide. When light needs to be transmitted through the first surface to the upper and lower layers, the wide-area design performed on the waveguide surface by the present application, for example, the alignment of the upper and lower waveguide layers is performed through the area 104, so that the optical coupling with large tolerance and low loss can be realized, and the product yield can be improved. The ratio of the width of the square region to the first width may be 2 to 1000 times, but is not limited thereto, and may be set as desired so that the alignment of the upper and lower layer waveguides is achieved by a wider region.

In the conventional end face coupling method, a certain spot-size conversion structure is used for coupling the emergent end face of the waveguide with a second waveguide, such as an optical fiber end face, laser is transmitted to the end face at the other end of the optical fiber along the optical fiber for emergent, the final coupling loss is still very large (generally greater than 5dB), the integration level is not high, and meanwhile, the end face needs to be processed to a degree suitable for coupling. End-to-end alignment requires a high alignment requirement (i.e., a low alignment tolerance) in all three mutually perpendicular directions. In comparison, the waveguide provided by the application realizes evanescent wave coupling between the waveguide and the waveguide positioned below the waveguide by designing the surface, reduces the difficulty of coupling alignment by designing the wide area of the waveguide surface, has higher alignment tolerance in three mutually perpendicular directions, and can improve the yield of products.

According to other embodiments of the present application, as shown in fig. 3, a taper branch structure may be further disposed at the end of the waveguide by designing a waveguide segment at the light emitting end, so as to implement evanescent coupling between the upper and lower waveguides to obtain optical coupling with large tolerance and low loss.

As shown in fig. 3, the first surface may further include, along the length direction a of the waveguide: one or more sub-regions 110 located to the right of the second region 102, wherein the width of the sub-region 104 decreases along the length of the waveguide such that light can be transmitted from the one or more sub-regions 110 to the second waveguide located below the first surface via evanescent coupling. The width of at least one of the sub-regions 104 decreases linearly with increasing length of the waveguide along its length, i.e., a taper structure, so that optical coupling can achieve low loss through a branched structure at the end of a wide waveguide. For example, the narrowest portion of the sub-region 104 may have a width of 100-200nm, and the corresponding length of the taper structure may not be too short, for example, the aspect ratio may be greater than 100.

The optical assembly 10 as shown in fig. 4 may include: a first device, which may include a first waveguide, which may be the waveguide 100 described above; and a second device, which may include a second waveguide 200, wherein the first device and the second device may be coupled with a third region 202 of a second surface 201 of the second waveguide 200 through at least a portion 108 of the second region 102 of the first surface of the first waveguide 100.

Fig. 5 is a schematic diagram showing the structure of an optical component formed by heterointegration of a III-V laser prepared on a silicon-based silicon oxide layer and a lithium niobate LNOI chip or SOI chip, etc., wherein the InGaAsP waveguide and the above layers in fig. 5 form a flip-chip bonded laser chip, the lower layers are passive waveguide chips prepared by additional processing, and the refractive index of the waveguide on the chip is only required to be larger than that of the silicon dioxide buried oxide layer on the laser chip. Since the width of the general waveguide on the optical chip is in the micrometer level, in order to set a waveguide with a width of tens of micrometers or even hundreds of micrometers in the bonding region, the above-mentioned width gradual change is needed to be used to generate an adiabatically gradual change structure, such as a taper structure, to connect two waveguides with different widths, the length of the taper is determined according to the practical situation of the width difference of the wide and narrow waveguides, and needs to be long enough to ensure that the loss introduced by the taper structure is small enough. The waveguide layer of the laser core layer is represented as two sections of areas with different color depths, wherein a small section with darker left color corresponds to an active medium of the laser and is a luminous area, a section with lighter right color can be a passive waveguide with a slightly shorter forbidden band wavelength so as not to absorb light emitted by the left section, or can be a waveguide completely identical to the active medium, and at the moment, a gain can be arranged at the position to form a Semiconductor Optical Amplifier (SOA) so as to avoid too large optical loss caused by absorption and provide tunable power control. The patterns of the respective waveguides of the two chips in the bonding region are set to be the patterns of the surfaces of the

waveguides

100 and 200, so that the effects of good alignment and small alignment deviation can be achieved, wherein the waveguide of the laser covers the waveguide of the passive chip, the widths of the two waveguides are equivalent, the two dielectric layers can be directly bonded between molecules, and the dielectric layers can also be coated with thin layers of media such as BCB (bulk-dielectric-boron) and the like for auxiliary bonding. Accordingly, the optical assembly 10 may further include a dielectric auxiliary layer between the first device and the second device.

At the end of the wide waveguide of the two devices, a taper structure can be arranged. Each branch taper on one waveguide can be the same so as to ensure that the phases at different positions of the wide mode field are basically kept the same or different, the width of each branch taper is reduced from micrometer-level heat insulation to about 100-200nm, and the thinner the branch taper is, the better the light scattering loss caused by medium refractive index mutation can be reduced; the length of the branch tap needs to be long enough to reduce coupling and scattering losses.

As shown in fig. 6, the third region 202 includes, along the length direction a of the waveguide: a fourth region 203 having a fourth width, wherein the fourth width is comparable to the width of at least a portion 108 of the second region 102 such that the first waveguide 100 and the second waveguide 200 can be disposed in alignment.

According to further embodiments of the present application, as shown in fig. 7, the third region 202 further comprises one or more second sub-regions 204 located to the left of the fourth region 203, wherein the width of the second sub-regions 205 increases along the length direction of the waveguide.

According to some embodiments of the application, the first device is an active device and the second device is a passive device. The first device includes at least one of: a laser, an optical amplifier, and a photodetector, the first waveguide may be an InGaAsP waveguide and the second waveguide may be a lithium niobate waveguide, a silicon waveguide, or an amorphous silicon waveguide.

When the first device is a laser, the waveguide provided by the application can be used for improving a laser emitted from a common end, a waveguide structure is left at the laser emitting end of the laser during chip preparation, the waveguide width is gradually increased to dozens of micrometers or even hundreds of micrometers from the micrometer level at a laser resonant cavity through a structure with gradually increased width, such as a taper structure, and the length of the taper needs more than millimeters. The width of the waveguide after the taper, which is tens of microns wide, can be kept constant, and the length is selected to be sufficient, for example, several hundred microns, according to the evanescent coupling condition. And reducing the thickness of the cladding to a level equal to or slightly less than the wavelength of light by wet etching or dry etching so as to realize efficient evanescent coupling in the later period. The waveguide on the second device, such as a passive waveguide chip, may be the above-mentioned second waveguide proposed in this application, and the width is usually also on the micrometer scale, and the width thereof may be increased to tens or hundreds of micrometers by a taper structure, and then a waveguide with a width of tens of micrometers is constant. And aligning the tail waveguide with locally thinned upper cladding layer of the laser with the wide waveguide of the passive chip, and performing interface bonding in the chip surface, including direct thermal bonding and bonding realized by mediation of a polymer film. Thus, the alignment of two waveguides with widths of tens or hundreds of micrometers in the width direction can achieve a large 1dB alignment tolerance (e.g., not less than ± 10 micrometers); in the direction of the thickness of the waveguide, because the interfaces of the two chips are bonded, the adjustment of precise alignment is not needed, and only the complete bonding and bonding of the two interfaces are ensured; in the optical axis direction of light propagation, because the butt joint of two optical fields is realized through the wave guide effect of the waveguide, the selection of the proper wide waveguide length can realize large alignment tolerance, for example, when the alignment deviation of hundreds of micrometers exists in the direction, the relative change of the coupling loss can be controlled within 0.25dB and hardly changes.

Other embodiments of the present application also provide a chip, which may include the optical assembly described above. For example, optoelectronic devices and monolithically integrated chips of microelectronic devices are realized by conventional microelectronic CMOS processes, and silicon-based large-scale integration techniques using photons and electrons as information carriers may be researched and developed.

Other embodiments of the present application also provide an optical quantum integrated chip, which includes the above optical assembly, such as the integrated structure shown in fig. 5. The bonding laser can reduce the loss of pump light and realize quantum light source with enough brightness with smaller total power.

Still other embodiments of the present application provide a method of optical component integration, comprising: respectively preparing a first device and a second device, wherein the first device comprises a first waveguide which is the waveguide provided by the application, and the second device comprises a second waveguide which can be the second waveguide provided by the application; and bond coupling the first device and the second device such that light can be transmitted to the second waveguide via evanescent coupling through at least a portion of the second region of the first waveguide.

Still other embodiments of the present application further provide a method of optoelectronic heterogeneous integration, which includes the aforementioned method of device integration.

Such as the hetero-integration of a III-V laser fabricated on a silicon substrate silicon dioxide layer with a lithium niobate LNOI chip, the hetero-integration of a III-V laser fabricated on a silicon substrate silicon dioxide layer with a SOI chip, the hetero-integration of a conventional mature III-V laser fabricated on an InP substrate with a SOI chip, and the hetero-integration of a conventional mature III-V laser fabricated on an InP substrate with an LNOI chip via an amorphous silicon waveguide.

The technology can be used for bonding and integrating the laser and the passive waveguide chip (lithium niobate, silicon nitride and other chips) which are respectively prepared, has smaller coupling loss and larger alignment tolerance, and can obviously improve the yield of products.

The photoelectric heterogeneous integration technology provided by the application can realize optical interconnection between chips and in the chips, and can effectively solve the problems of bandwidth, power consumption, time delay and the like of the existing metal interconnection of microelectronic chips.

The application of these integration methods is not limited to the material systems given above or in the drawings, such as silicon nitride in addition to lithium niobate, etc., and the relationship between the refractive indices of the two chip waveguides may also include the case of equality, such as the waveguides being the same medium on both sides; it should be further noted that this heterogeneous integration method is not limited to the integration of the laser and the passive chip mainly described above, but also includes bonding integration between the optical amplifier or the optical detector and the passive chip, and integration between any two or more of the laser, the optical amplifier, the passive chip, and the optical detector, and integration or connection between two different chips of the same device (for example, the passive waveguide network chip implements network scale expansion in an in-plane or stacked form by waveguide bonding and docking).

The integration method provided by the application can replace the following coupling modes of a laser, a light detector and a chip: the vertical grating coupler, the end face coupling and the heterogeneous material substrate are directly grown to prepare the laser or the optical detector, can be used for integrating optical waveguide devices such as the laser, the optical amplifier, the passive waveguide chip, the optical detector and the like which are respectively prepared, can have smaller coupling loss and larger alignment tolerance, and can obviously improve the product yield.

As shown in fig. 8, an optical assembly may include a first device 11, which may include a first waveguide 100; a second device 12, which may include a second waveguide 200; and a third waveguide 20 located between the first waveguide 100 and the second waveguide, wherein the first device 11 and the second device 12 are coupled with a third region of the second surface of the third waveguide 20 through at least a part of the second region of the first surface of the first waveguide, such that light can be transmitted to the second waveguide 200 through the first waveguide 100 and the third waveguide 20 via evanescent coupling.

According to some embodiments of the present application, as in the structure of the aforementioned second waveguide 200, as shown in fig. 6, the third region 202 includes, along the length direction of the first waveguide: a fourth region 203 having a fourth width, wherein the fourth width is comparable to the width of at least a portion 108 of the second region such that the first waveguide 100 and the second waveguide 200 can be disposed in alignment.

As shown in fig. 7, the third region 202 further comprises one or more second sub-regions 204 located to the left of the fourth region, wherein the width of the second sub-regions 205 increases along the length direction of the waveguide.

According to some embodiments of the present application, as shown in fig. 8, fig. 8 illustrates a case of bonding a laser based on a lattice constant matched III-V material substrate (where the first waveguide is an InGaAsP waveguide, the second waveguide is a lithium niobate waveguide, and the third waveguide is an amorphous silicon taper waveguide), such as an InGaAsP laser based on an InP substrate, which is mature at present, can obtain a power significantly higher than that of the current silicon-based laser, and can reach a level of 100mW, which is beneficial for applications with high requirements on laser power. At this time, different from the case that the lower cladding is made of silicon dioxide, because the refractive index difference of the core cladding is obviously smaller than that of the core cladding and air, if the air cladding is used, the mode field is seriously asymmetric, and the available power of the traditional laser is influenced; for this purpose, a few microns thick InP cladding is kept at the laser cavity, and an upper cladding with an adiabatic reduction in thickness is fabricated by etching between the active region and the following passive waveguide or SOA section, so that the thickness of the upper cladding between the first waveguide and the third waveguide in the bonding region is reduced to a suitable level for evanescent coupling (typically at the wavelength level or slightly less).

Such a dielectric layer having an adiabatic variation in thickness may be prepared by a shadow masked photolithography or a shadow masked PECVD (RIE) process. When the refractive index of the waveguide medium on the passive waveguide chip is higher than that of the lower cladding of the waveguide of the laser chip, the waveguides on the two devices (chips) can be directly in contact bonding, for example, the waveguides are coupled into a silicon waveguide by InGaAsP (the refractive index of silicon is slightly larger than that of InGaAsP and InP); however, if the refractive index of the passive waveguide is equal to or even smaller than that of the lower cladding of the laser waveguide, when the width of the branch tap of the laser waveguide is reduced, the optical field will not be coupled into the passive chip waveguide by evanescent waves, but will be radiated into the substrate of the laser via the lower cladding of the laser waveguide and lost. For this purpose, a layer of material with a higher refractive index than that of InP may be grown on the waveguide of the passive chip to form an air-clad waveguide. Fig. 8 shows the case where a third waveguide, such as an amorphous silicon waveguide, is grown on a second waveguide, such as a lithium niobate waveguide, and laser light is coupled into the amorphous silicon waveguide from the InGaAsP waveguide, and then light is coupled into the lithium niobate waveguide by a single tap of the amorphous silicon waveguide. The tapering of the thickness along the length of the first waveguide through the surface of the upper cladding opposite the third waveguide enables light to be transmitted through the first waveguide to the third waveguide via evanescent coupling.

The integration method can be used for integrating the active devices (lasers and optical detectors) and the passive waveguide device chips which are prepared independently, the processes of the active devices and the passive chips are generally different and are not compatible with each other, the independent preparation can ensure that the active devices and the passive chips have higher yield respectively, the product yield can be improved through the device integration method, and the product cost of the integration of the lasers and the passive chips is obviously reduced.

The technical content and technical features of the present application have been disclosed as above, however, one skilled in the art may make various substitutions and modifications based on the teaching and disclosure of the present application without departing from the spirit of the present application. Therefore, the protection scope of the present application should not be limited to the disclosure of the embodiments, but should include various alternatives and modifications without departing from the scope of the present application, which is covered by the claims of the present patent application.

Claims

1. A waveguide having a first surface comprising, along a length of the waveguide:

a first region having a first width; and

a second region having a second width, wherein the second width is greater than the first width;

wherein the waveguide is configured to enable light to be transmitted to the second waveguide via evanescent coupling through at least a portion of the second region.

2. The waveguide of claim 1, wherein the second region comprises a tapered region that increases in width along a length of the waveguide.

3. The waveguide of claim 1, wherein the second region comprises a region of constant width along the length of the waveguide.

4. The waveguide of claim 1, wherein the first surface further comprises, along a length of the waveguide:

one or more sub-regions to the right of the second region;

wherein the widths of the sub-regions decrease along a length direction of the waveguide such that light can be transmitted from the one or more sub-regions to the second waveguide via evanescent coupling.

5. The waveguide of claim 4, wherein the width of at least one of the sub-regions decreases linearly with increasing length of the waveguide along its length direction.

6. An optical assembly, comprising:

a first device comprising a first waveguide, the first waveguide being a waveguide according to any one of claims 1-5; and

a second device comprising the second waveguide,

wherein the first device and the second device are coupled with the third region of the second surface of the second waveguide through at least a portion of the second region of the first surface of the first waveguide.

7. The optical assembly of claim 6, wherein the third region comprises, along a length of the waveguide: a fourth region having a fourth width, wherein the fourth width is commensurate with a width of the at least a portion of the second region such that the first waveguide and the second waveguide can be disposed in alignment.

8. The optical assembly of claim 7, wherein the third region further comprises one or more second sub-regions to the left of the fourth region, wherein the second sub-regions increase in width along the length of the waveguide.

9. The optical assembly of claim 6, further comprising a dielectric auxiliary layer between the first and second devices.

10. The optical assembly of claim 6, wherein the first device is an active device and the second device is a passive device.

11. The optical assembly of claim 6, wherein the first device comprises at least one of: a laser, an optical amplifier, and a photodetector.

12. The optical assembly of claim 6, wherein the first waveguide is an InGaAsP waveguide.

13. The optical assembly of claim 6, wherein the second waveguide is a lithium niobate waveguide, a silicon waveguide, or an amorphous silicon waveguide.

14. A chip comprising an optical component according to any one of claims 6-13.

15. An optical quantum integration chip comprising an optical assembly according to any one of claims 6 to 13.

16. A method of optical component integration, comprising:

separately fabricating a first device and a second device, wherein the first device comprises a first waveguide, the first waveguide being a waveguide according to any one of claims 1-5, the second device comprising the second waveguide; and

bonding the first device and the second device such that light can be transmitted to the second waveguide via evanescent coupling through the at least a portion of the second region of the first waveguide.

17. A method of optoelectronic heterointegration comprising the method of claim 16.