CN117930432A - Adiabatic wedge coupler applied to 2.5-dimensional heterogeneous integrated optical waveguide - Google Patents
Adiabatic wedge coupler applied to 2.5-dimensional heterogeneous integrated optical waveguide Download PDFInfo
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- 230000003287 optical effect Effects 0.000 title claims abstract description 40
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 94
- 238000010168 coupling process Methods 0.000 claims abstract description 68
- 230000008878 coupling Effects 0.000 claims abstract description 66
- 238000005859 coupling reaction Methods 0.000 claims abstract description 66
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 49
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 49
- 239000010703 silicon Substances 0.000 claims abstract description 49
- 239000004408 titanium dioxide Substances 0.000 claims abstract description 41
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 15
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 11
- 239000000758 substrate Substances 0.000 claims abstract description 10
- 238000005530 etching Methods 0.000 claims description 12
- 239000010410 layer Substances 0.000 claims description 9
- 238000005253 cladding Methods 0.000 claims description 6
- 239000011241 protective layer Substances 0.000 claims description 6
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 4
- 230000010354 integration Effects 0.000 abstract description 30
- 238000000034 method Methods 0.000 abstract description 27
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 238000005516 engineering process Methods 0.000 abstract description 4
- 230000008569 process Effects 0.000 description 19
- 239000000463 material Substances 0.000 description 17
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 6
- 230000005684 electric field Effects 0.000 description 6
- 238000005498 polishing Methods 0.000 description 6
- 238000009616 inductively coupled plasma Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 238000000151 deposition Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 239000012212 insulator Substances 0.000 description 4
- 238000000231 atomic layer deposition Methods 0.000 description 3
- 238000000609 electron-beam lithography Methods 0.000 description 3
- 238000001259 photo etching Methods 0.000 description 3
- 229920002120 photoresistant polymer Polymers 0.000 description 3
- 235000012431 wafers Nutrition 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 230000000295 complement effect Effects 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000004528 spin coating Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 238000000411 transmission spectrum Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000009022 nonlinear effect Effects 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- VDGJOQCBCPGFFD-UHFFFAOYSA-N oxygen(2-) silicon(4+) titanium(4+) Chemical compound [Si+4].[O-2].[O-2].[Ti+4] VDGJOQCBCPGFFD-UHFFFAOYSA-N 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/1228—Tapered waveguides, e.g. integrated spot-size transformers
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/12038—Glass (SiO2 based materials)
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/12061—Silicon
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Optical Integrated Circuits (AREA)
Abstract
The invention discloses an adiabatic wedge coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide, namely an adiabatic wedge coupler for heterogeneous integration, which structurally comprises a silicon dioxide substrate, a silicon waveguide and a titanium dioxide waveguide, wherein the silicon waveguide and the titanium dioxide waveguide are indirectly spliced by adopting a special wedge shape so as to realize adiabatic coupling of light in the heterogeneous waveguide. The novel 2.5-dimensional heterogeneous integration method refers to that optical waveguide devices are positioned on the same plane, and the function expansion of a heterostructure is carried out on the plane. The invention has the advantages of excellent performance, simpler design, more free coupling condition and easy manufacture, can provide a novel 2.5-dimensional integrated optical coupling scheme and basic technical support for the silicon-based heterogeneous integration technology, and opens up a new opportunity for 2.5-dimensional brand new type devices with performance superior to that of discrete optical elements.
Description
Technical Field
The invention belongs to an optical coupler in the field of silicon-based photoelectron and heterogeneous integration, and particularly relates to an adiabatic wedge-shaped coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide.
Background
Silicon materials are widely designed for SOI (silicon on insulator ) due to their limited ability, however, SOI-based optics are very sensitive to waveguide non-uniformity and sidewall roughness due to their high refractive index contrast, while silicon materials are poorly thermally stable. Titanium dioxide has COMS (complementary metal oxide semiconductor ) compatibility, a nonlinear refractive index, and a large band gap, and is thus widely used in nonlinear optical devices, but has a problem of large loss. In addition, lithium niobate is widely applied to high-performance electro-optical modulators, polarization controllers and nonlinear optical devices due to the characteristics of high electro-optical coefficient, wide transparent window, second-order nonlinear effect and the like, but is laborious in etching process due to low refractive index. The III-V materials are widely applied to lasers, detectors, amplifiers and modulators due to direct band gap and CMOS compatibility, but the materials are easy to lattice mismatch, the small refractive index leads to large device size, and conversely, the wafer size is small, and finally, the production cost is high. In addition, the polymer material has a negative thermo-optical coefficient, the metal material has a surface plasmon polarization effect, and the like.
The materials have different advantages and disadvantages, and the materials complement each other and have unique characteristics. Then the dominant complementation of the various materials can be achieved by heterogeneous integration? The answer is affirmative and many heterogeneous, hybrid integration have emerged. Conventional monolithic integration, which utilizes only a single material to design a planar waveguide device, has performance limitations. Thus, such a multi-material system integration scheme can greatly increase the functional variety and upper capability limits of the optical chip system. In design, material characteristics, device design and process compatibility are considered, and material combination is performed according to requirements.
Key indicators of heterogeneous integration are approaching or exceeding single integration or hybrid integration, with optimized active and passive heterogeneous integration opening new opportunities for completely new types of devices with superior performance over discrete optical components, but with limited integration process compatibility including challenges of structure size and stress limitations, material lattice mismatch, process temperature and conditions, coupling schemes including optical, electrical, and thermal coupling between different materials, etc. The invention provides a novel 2.5-dimensional integrated optical coupling scheme for a silicon-based heterogeneous integration technology.
Conventional 3-dimensional integration refers to the integration of multiple functional chips by stacking them vertically together to form a three-dimensional structure, utilizing direct bonding techniques to achieve the shortest interconnections and smallest package size. Unlike 3-dimensional integration, 2.5-dimensional integration refers to the integration of other functional materials, optoelectronic devices or chips on the same layer of substrate, the fabrication of chips by special semiconductor processes, the 2.5-dimensional packaging by connecting chips Through a Through-Silicon-Via (TSV) conversion board, and the enhancement or expansion of functions is realized by using extremely high interconnection density.
Disclosure of Invention
The invention provides an adiabatic wedge coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide based on 2.5-dimensional integration, which is an efficient low-loss evanescent coupling structure of optical transition with heterogeneous waveguides, namely an adiabatic wedge coupler for heterogeneous integration of a titanium dioxide waveguide and a silicon waveguide, and the two wedge-shaped heterogeneous waveguides are spliced indirectly without contact so as to realize adiabatic coupling of light in the heterogeneous optical waveguide. The novel 2.5-dimensional heterogeneous integration method refers to that optical waveguide devices are positioned on the same plane, and the function expansion of a heterostructure is carried out on the plane. The invention has the advantages of excellent performance, simpler design, more free coupling condition and easy manufacture, can provide a novel 2.5-dimensional integrated optical coupling scheme and basic technical support for the silicon-based heterogeneous integration technology, and opens up a new opportunity for 2.5-dimensional brand new type devices with performance superior to that of discrete optical elements.
The technical scheme adopted by the invention is as follows:
The invention discloses an adiabatic wedge coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide, which comprises a silicon dioxide substrate, a silicon waveguide and a titanium dioxide waveguide, wherein the silicon waveguide and the titanium dioxide waveguide are both of a strip-shaped square structure, one end of the silicon waveguide and the titanium dioxide waveguide is a plane end, the other end of the silicon waveguide is a wedge-shaped tip with a wedge surface, the wedge surface of the silicon waveguide and the wedge surface of the titanium dioxide waveguide are opposite and are arranged in parallel, the wedge-shaped tip of the silicon waveguide and the wedge-shaped tip of the titanium dioxide waveguide form a coupling area, the coupling gap of the coupling area, namely the distance between the wedge surface of the silicon waveguide and the wedge surface of the titanium dioxide waveguide is 0.15 mu m, and the coupling length of the coupling area is 25 mu m, so that adiabatic coupling of light in the heterogeneous waveguide is realized.
As a further improvement, the silicon dioxide substrate and the silicon waveguide of the invention also comprise a deposited aluminum oxide film on the upper surface for being used as a protective layer during etching of the titanium dioxide waveguide.
As a further improvement, the coupling ports of the silicon waveguide and the titanium dioxide waveguide adopt wedge-shaped tips, the coupling gap is 0.15 mu m, and the coupling length is 25 mu m of the wedge-shaped tip part of the silicon waveguide.
As a further improvement, the entire surface of the adiabatic wedge coupler of the present invention is coated with a deposited silica cladding for protection.
The invention discloses the following technical effects:
The invention discloses an efficient low-loss optical transition evanescent coupling structure with heterogeneous waveguides, which realizes an adiabatic coupler by indirectly splicing two waveguide structures with wedge-shaped tips. The light mixed mode in the waveguide is transmitted to the wedge-shaped tip through the silicon waveguide, and is coupled into the titanium dioxide wedge-shaped tip through the wedge-shaped tip coupling part as the wedge-shaped tip continuously advances and changes, and finally is output through the titanium dioxide waveguide. The coupling process of the wedge-shaped tip coupling part is a gradual process, and the refractive index change of the wedge-shaped tip coupling part corresponding to the mixed mode is gradual along with the longer length of the wedge-shaped tip coupling part, namely the abrupt change is smaller, and the corresponding loss is smaller, so that efficient adiabatic coupling can be realized in this way.
The invention utilizes silicon waveguides and titania waveguides to achieve novel 2.5-dimensional heterogeneous integration on silicon-on-insulator (SOI) wafers. The titanium dioxide has CMOS compatibility, nonlinear refractive index and large band gap, and is widely applied to lasers, detectors, modulators and the like, so that the technology can realize low-loss transmission of optical signals in the silicon waveguide to the titanium dioxide waveguide and realize optical device coupling of heterogeneous materials, thereby solving the problems of small transparent window, performance limitation, active functions and the like of the silicon-based optical chip and greatly enhancing the functional variety and the upper limit of the capability of the optical chip system.
The invention discloses a preparation process of an adiabatic wedge coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide, which is different from the current mainstream stacked 3-dimensional integrated design, and does not need to undergo a common 3-dimensional integrated process, namely a plurality of strict processes such as deposition, photoetching, polishing, etching, bonding and the like. In addition, 3-dimensional packaging requires a highly difficult manufacturing process for performing direct bonding techniques. Therefore, the harsh polishing and bonding processes present a great challenge to the accuracy of the coupler structure dimensions and greatly affect the yield. Notably, 3-dimensional heterogeneous integrated optical designs require short interconnect coupling lengths to reduce losses and improve compactness, while the shorter the coupling length, the more strongly the effect of non-uniformity of the Chemical Mechanical Polishing (CMP) process. If a long-distance grating coupling mode is adopted, the design is complex and the coupling condition is limited. Therefore, compared with 3-dimensional integration, the 2.5-dimensional integration method provided by the invention has the advantages that heterostructures are positioned on the same plane, complicated and strict polishing, bonding and direct bonding processes in 3-dimensional are avoided in the integration process, the coupling gap between heterogeneous waveguides can be well controlled, and the limitation of 3-dimensional integration coupling conditions is avoided in the design. In addition, the preparation method of the high-efficiency asymmetric directional coupler applied to the 2.5-dimensional heterogeneous integrated optical waveguide skillfully adopts the aluminum oxide film as a protective layer, avoids partial photoetching, etching, polishing and other processes, and greatly simplifies the process steps. Therefore, the invention is simpler in design, free in coupling condition and simpler in process steps.
Drawings
Fig. 1 is a three-dimensional schematic diagram of an adiabatic wedge coupler for a 2.5-dimensional heterogeneous integrated optical waveguide in accordance with the present invention. In the figure, 1 is a silicon dioxide substrate, 2 is a silicon waveguide, and 3 is a titanium dioxide waveguide; inside the rectangular dashed line is a wedge-shaped tip coupling portion;
FIG. 2 is a graph of coupling loss at 1550nm wavelength for (a) different titania waveguide heights, (b) different titania waveguide widths, and (c) different silicon waveguide chamfer portion lengths for an adiabatic wedge coupler structure for a 2.5-dimensional heterogeneous integrated optical waveguide in accordance with the present invention;
FIG. 3 is a graph of the transmission spectrum of a structure of an adiabatic wedge coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide in the wavelength range 1450nm to 1650nm in accordance with the present invention;
Fig. 4 is a graph of the electric field at 1550nm (x-y plane) and a graph of the electric field cross section at different locations (y-z plane) for an adiabatic wedge coupler structure applied to a 2.5-dimensional heterogeneous integrated optical waveguide in accordance with the present invention.
Detailed Description
The technical scheme of the invention is further described below through specific embodiments with reference to the accompanying drawings.
As shown in fig. 1, the invention discloses an adiabatic wedge coupler applied to a 2.5-dimensional heterogeneous integrated optical waveguide, which comprises a silicon dioxide substrate 1, a silicon waveguide 2 and a titanium dioxide waveguide 3 which are positioned on the silicon dioxide substrate 1, wherein the silicon waveguide 2 and the titanium dioxide waveguide 3 are of long-strip square structures, one end is a plane end, the other end is a wedge-shaped tip with a wedge surface, the wedge surface of the silicon waveguide 2 and the wedge surface of the titanium dioxide waveguide 3 are opposite and are arranged in parallel, the wedge-shaped tip of the silicon waveguide 2 and the wedge-shaped tip of the titanium dioxide waveguide 3 form a coupling area, the coupling gap of the coupling area, namely the distance between the wedge surface of the silicon waveguide 2 and the wedge surface of the titanium dioxide waveguide 3 is 0.15 μm, and the coupling length of the coupling area is 25 μm, so that adiabatic coupling of light in the heterogeneous waveguide is realized. The silicon waveguide 2 has a width a of 0.5 μm and a height b of 0.22 μm; the width c of the titania waveguide 3 was designed to be 1 μm and the height d was designed to be 0.3 μm. Inside the rectangular broken line in the figure is a wedge-shaped tip coupling portion, the length of which is defined as 25 μm for the wedge-shaped tip portion length L of the silicon waveguide 2, and the internal coupling gap is 0.15 μm. The invention adopts optical waveguide devices of different materials to carry out heterogeneous integration on 2.5 dimension, namely the optical waveguide devices are positioned on the same plane, and the function expansion of the heterostructure is carried out on the plane.
As a further improvement, in the process preparation, the upper surface formed by the silicon dioxide substrate 1 and the silicon waveguide 2 also comprises a deposited aluminum oxide film which is used as a protective layer in the etching of the titanium dioxide waveguide 3. In addition, the entire surface of the adiabatic wedge coupler described herein is coated with a layer of deposited silica cladding for protection. The alumina film and the silica cladding are only optimized steps in the process, and have no effect on the function of the whole asymmetric directional coupler, so the alumina film and the silica cladding are not illustrated in fig. 1. The invention carries out simulation by a Finite-difference method (FDTD) of the time Domain, so as to determine the optimal structure size and obtain a final transmission spectrogram and an electric field diagram of the structure. The input light source is a TE basic Mode centered on 1550nm wavelength, and a Mode decomposition monitor (Mode expansion) is added on the output monitor to filter out the influence of unwanted modes, the monitor is used for decomposing the Mode total field recorded by a specified monitor into the specified Mode of the waveguide where the monitor is positioned, and only the TE basic Mode is seen. In the simulation, the refractive index of the silicon waveguide 2 is set to 3.478, and the refractive index of the titanium dioxide 3 waveguide is set to 2.3.
First, as shown in FIG. 2 (a), the height d of the scanned titania waveguide 3 is from 0.1 μm to 0.6 μm, and the coupling loss is minimized at d of 0.3. Mu.m. Next, as shown in FIG. 2 (b), keeping d at 0.3 μm, the coupling loss is minimized when the width c of the scanned titania waveguide 3 is from 0.5 μm to 1.5 μm, and c is 1. Mu.m. Thus, the structural dimensions of d=0.3 μm, c=1 μm are chosen.
The invention realizes the adiabatic coupler by indirectly splicing two waveguide structures with wedge-shaped tips. The light mixed mode in the waveguide is transmitted to the wedge-shaped tip through the silicon waveguide 2, and as the wedge-shaped tip continuously advances, the mixed mode is coupled from the silicon waveguide 2 into the wedge-shaped tip of the titanium dioxide waveguide 3 through the wedge-shaped tip coupling part, and finally is output through the titanium dioxide waveguide 3. The coupling process of the wedge-shaped tip coupling part is a gradual process, and the refractive index change of the wedge-shaped tip coupling part corresponding to the mixed mode is gradual along with the longer length of the wedge-shaped tip coupling part, namely the abrupt change is smaller, and the corresponding loss is smaller, so that efficient adiabatic coupling can be realized in this way. Therefore, as shown in fig. 2 (c), the length L of the coupling portion of the scanning wedge-shaped tip is from 5 μm to 50 μm, and the coupling loss is smaller as L is larger, but when L reaches 25 μm, the loss reaches equilibrium with little variation, and therefore, in order to obtain the ideal coupling efficiency and in consideration of the precision problem of the process preparation, the present invention selects gap to be 0.15 μm and L to be 25 μm.
As shown in FIG. 3, the transmission spectrum of the structure at 1450-1650nm, the transmittance at 1550nm is about-0.5 dB (88.99%), and the performance index is equivalent to that of a common 3-dimensional hetero-coupler.
As shown in fig. 4, which is an electric field diagram of the whole structure and an electric field diagram of each section, it can be seen that the electric field is gradually coupled from the silicon waveguide 2 to the titanium dioxide 3 waveguide.
The preparation process of the invention is carried out by skillfully adopting the alumina protective layer, avoiding complex processes of photoetching, etching, polishing and the like, and comprises the following steps:
1) Using a standard silicon-on-insulator (Silicon On Insulator, SOI) wafer with a height of 220nm, spin-coating photoresist on the sample and patterning and etching the silicon waveguide 2 by electron beam exposure (Electron Beam Lithography, EBL) and inductively coupled plasma etching (Inductively coupled plasma, ICP);
2) An atomic layer deposition (Atomic Layer Deposition, ALD) is used for depositing an alumina film with the thickness of 20nm, which is used as a protective layer when the titanium dioxide waveguide 3 is etched, and the very thin alumina film layer has no influence on the waveguide coupling structure;
3) Continuously depositing a 0.3 mu m titanium dioxide heterogeneous material layer by using Plasma Enhanced Chemical Vapor Deposition (PECVD), spin-coating photoresist on the titanium dioxide heterogeneous material layer for the second time, and carrying out pattern design and etching on the titanium dioxide waveguide 3 by using electron beam Exposure (EBL) and inductively coupled plasma etching (ICP), wherein when the titanium dioxide heterogeneous material layer is etched to an alumina film layer, etching is still until the unnecessary titanium dioxide material is completely removed;
4) And after stripping the photoresist, forming a silicon-titanium dioxide heterogeneous waveguide coupler structure, and finally, depositing a silicon dioxide cladding layer as the protection of the whole coupler structure.
In conclusion, the novel 2.5-dimensional silicon-based heterogeneous integrated adiabatic taper coupler provided by the invention has the coupling efficiency of 88.9% and the coupling length of 25um. The results show that not only the performance of 2.5-dimensional integration is comparable to that of 3-dimensional, but also the design is simpler, the coupling conditions are more free, and the process is simpler.
The above-described embodiments are intended to illustrate the present invention, not to limit it, and any modifications and variations made thereto are within the spirit of the invention and the scope of the appended claims.
Claims (4)
1. An adiabatic wedge coupler for 2.5-dimensional heterogeneous integrated optical waveguides, characterized in that: the device comprises a silicon dioxide substrate, a silicon waveguide and a titanium dioxide waveguide, wherein the silicon waveguide and the titanium dioxide waveguide are both in a strip square structure, one end of the silicon waveguide and the titanium dioxide waveguide is a plane end, the other end of the silicon waveguide is a wedge-shaped tip with a wedge surface, the wedge surface of the silicon waveguide and the wedge surface of the titanium dioxide waveguide are opposite and are arranged in parallel, the wedge-shaped tip of the silicon waveguide and the wedge-shaped tip of the titanium dioxide waveguide form a coupling area, the coupling gap of the coupling area, namely the distance between the wedge surface of the silicon waveguide and the wedge surface of the titanium dioxide waveguide is 0.15 mu m, and the coupling length of the coupling area is 25 mu m, so that adiabatic coupling of light in a heterogeneous waveguide is realized.
2. The adiabatic wedge coupler for 2.5-dimensional heterogeneous integrated optical waveguides of claim 1, wherein: the upper surface formed by the silicon dioxide substrate and the silicon waveguide also comprises a layer of deposited aluminum oxide film which is used as a protective layer during etching of the titanium dioxide waveguide.
3. The adiabatic wedge coupler for 2.5-dimensional heterogeneous integrated optical waveguides of claim 1, wherein: the coupling ports of the silicon waveguide and the titanium dioxide waveguide adopt wedge-shaped tips, the coupling gap is 0.15 mu m, and the coupling length is 25 mu m as the length of the wedge-shaped tip part of the silicon waveguide.
4. The adiabatic wedge coupler for 2.5-dimensional heterogeneous integrated optical waveguides of claim 1, wherein: the surface of the whole adiabatic wedge coupler is coated with a deposited silicon dioxide cladding for protection.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311859464.3A CN117930432A (en) | 2023-12-30 | 2023-12-30 | Adiabatic wedge coupler applied to 2.5-dimensional heterogeneous integrated optical waveguide |
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| CN202311859464.3A CN117930432A (en) | 2023-12-30 | 2023-12-30 | Adiabatic wedge coupler applied to 2.5-dimensional heterogeneous integrated optical waveguide |
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