WO2021175082A1 - Spot size converter and silicon-optical integrated chip - Google Patents
Spot size converter and silicon-optical integrated chip Download PDFInfo
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- WO2021175082A1 WO2021175082A1 PCT/CN2021/075243 CN2021075243W WO2021175082A1 WO 2021175082 A1 WO2021175082 A1 WO 2021175082A1 CN 2021075243 W CN2021075243 W CN 2021075243W WO 2021175082 A1 WO2021175082 A1 WO 2021175082A1
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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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/14—Mode converters
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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
- G02B6/10—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
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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
- G02B6/10—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
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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
- G02B6/10—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
- G02B2006/12133—Functions
- G02B2006/12152—Mode converter
Definitions
- This application relates to the field of optical communication technology, and in particular to a mode spot converter and a silicon optical integrated chip.
- Silicon optical chip is a key technology to realize optical interconnection, which can effectively reduce the cost of modules in optical communication.
- the size of a typical single-mode silicon waveguide is 420nm ⁇ 220nm, while the size of a single-mode fiber is about 9 ⁇ m.
- the coupling efficiency of the direct coupling between the two is too low, and special devices are required to achieve the two Efficient coupling between participants.
- the current common coupling schemes include the vertical coupling mode of the grating coupler and the horizontal coupling mode of the spot size converter (Spot Size Converter, SSC).
- the grating coupler is made by fabricating a grating structure on a silicon waveguide.
- the mode spot converter When light is incident on the surface of the grating coupler from an optical fiber, it achieves effective coupling with the optical fiber placed above the chip through the Bragg diffraction effect.
- This method can improve the alignment tolerance between the optical fiber and the coupler, but the coupling efficiency is low and the wavelength is sensitive, which is not conducive to packaging, and is often used to test chips. Therefore, the mode spot converter is often used for horizontal coupling in the product, and the coupling efficiency is high.
- the mode spot converter of the layer ladder structure includes two core layers with different thicknesses: a first core layer 10' and a second core layer 20'.
- the first core layer 10' includes a first wedge structure 11' and a first linear structure 12'
- the second core layer 20' includes a second wedge structure 21' and a second linear structure 22'
- the second wedge structure 21' and the first linear structure 12' form a stepped wedge structure.
- the thickness of the first core layer 10' is relatively thin, and the tip of the first wedge structure 11' is coupled to the external optical fiber, and the optical field distribution at the tip of the first wedge structure 11' is better than the optical field distribution in the optical fiber. Coincidence, higher coupling efficiency.
- the first wedge-shaped structure 11' is laterally widened to the first linear structure 12'.
- the thickness of the second core layer 20' needs to be consistent with the thickness of the top silicon of the external silicon optical device, which is thicker than the first core layer 10'.
- the wedge structure 21' is coupled with the first linear structure 12' to realize the transformation of the light mode from the first core layer 10' to the second core layer 20'.
- the tip of the wedge-shaped structure is limited by the semiconductor processing technology, and the size is difficult to be infinitely small, and it is easy to introduce polarization-dependent loss, that is, the light in the horizontal polarization mode (TE mode) is gradual from the thinner-thickness waveguide to the normal-thickness waveguide.
- the loss is small, and the optical loss in the vertical polarization mode (TM mode) is large, and the overall mode spot converter has a large polarization-dependent loss.
- the polarization-dependent loss when coupling from the first core layer to the second core layer is shown in Fig. 2.
- the wedge-shaped structure has a small loss, but for the TM mode, the wedge-shaped structure has a large loss, which introduces a large polarization-dependent loss.
- the purpose of the present application is to provide a mode spot converter and a silicon-optical integrated chip, which has extremely small polarization-related loss, higher coupling efficiency and better thermal stability.
- the present application provides a mode spot converter having a first end face optically coupled with an external optical fiber and a second end face optically coupled with an external optical device, characterized in that the mode spot converter include:
- the first optical waveguide includes a first wedge structure and a second wedge structure, the tip of the first wedge structure is adjacent to the first end surface, and the tip of the second wedge structure faces the same as the tip of the first wedge structure Back direction
- the second optical waveguide includes a third wedge-shaped structure that at least partially overlaps the second wedge-shaped structure to adiabatically couple the optical mode in the second wedge-shaped structure into the third wedge-shaped structure ;
- the tip of the third wedge-shaped structure faces the first wedge-shaped structure.
- the mode spot converter further includes a substrate and a lower cladding layer provided on the substrate, and the first optical waveguide and the second optical waveguide are provided on the lower cladding layer.
- an intermediate cladding layer is further provided between the first optical waveguide and the second optical waveguide, and the refractive index of the intermediate cladding layer is smaller than the refractive index of the first optical waveguide and the second optical waveguide.
- the thickness of the intermediate cladding layer is less than or equal to 3 microns.
- the first end surface is provided with a hollow portion below the first optical waveguide near the substrate of the undercladding layer.
- the first optical waveguide is a silicon waveguide
- the second optical waveguide is a silicon nitride waveguide
- the silicon waveguide is located above the under-cladding layer
- the silicon nitride waveguide is located on the Above the silicon waveguide.
- the thickness of the first optical waveguide is less than or equal to the thickness of the second optical waveguide.
- the thickness of the first optical waveguide is in the range of 60-200 nm, and the thickness of the second optical waveguide is in the range of 200-800 nm.
- the width of the tip cross section of the first wedge structure is less than or equal to 200 nm; the width of the tip cross section of the third wedge structure is in the range of 100 nm to 300 nm.
- the second optical waveguide further includes an edge coupling structure, one end of the edge coupling structure is connected to the tip of the third wedge structure, and the other end is deviated from the central axis of the second optical waveguide.
- the edge of the first optical waveguide extends to adiabatically couple the optical mode in the first optical waveguide into the second optical waveguide.
- the cross-sectional width of one end of the edge coupling structure away from the third wedge structure is less than or equal to 200 nm.
- an end of the edge coupling structure away from the third wedge structure extends out of the edge of the first optical waveguide.
- the second optical waveguide further includes a linear structure, and the linear structure is provided between the third wedge-shaped structure and the second end surface.
- the application also provides a silicon optical integrated chip, including a substrate, a lower cladding layer, a top layer of silicon, a silicon nitride layer, and an upper cladding layer; the top layer of silicon is provided with an optically active device, and the silicon nitride layer Equipped with silicon nitride optical waveguide;
- the mode spot converter of any one of the above-mentioned embodiments is provided on the silicon optical integrated chip adjacent to the coupling end surface of the silicon optical integrated chip and the external optical fiber;
- the optical signal output by the external optical fiber is coupled to the second optical waveguide via the first optical waveguide of the mode spot converter and transmitted into the silicon nitride optical waveguide, and is coupled to the silicon nitride optical waveguide via the silicon nitride optical waveguide.
- the mode matching degree between the mode spot converter and the external fiber is improved, the polarization-related loss between the two optical waveguides in the mode spot converter is reduced, and the thermal stability of the optical waveguide in the silicon optical integrated chip is improved. , Thereby reducing the optical transmission loss in the silicon optical integrated chip.
- FIG. 1 is a schematic diagram of the structure and cross-sectional view of a mode spot converter in the prior art
- FIG. 2 is a schematic diagram of polarization dependent loss of mode conversion coupling of the mode spot converter in FIG. 1;
- FIG. 3 is a schematic diagram of the structure and cross-section of the mode spot converter according to Embodiment 1 of the application; FIG.
- FIG. 4 is a schematic longitudinal cross-sectional view of the mode spot converter in FIG. 3 along the central axis;
- FIG. 5 is a schematic diagram of the structure and cross-sectional view of the mode spot converter according to Embodiment 2 of the application;
- FIG. 6 is a schematic diagram of the polarization dependent loss of the mode conversion coupling of the mode spot converter in FIG. 5;
- FIG. 7 is a schematic diagram of a longitudinal section and an end face of the mode spot converter according to Embodiment 3 of the application;
- FIG. 8 is a partial schematic diagram of a silicon optical integrated chip according to Embodiment 4 of the application.
- relative position in space are for the purpose of facilitating explanation to describe a unit or feature as shown in the drawings relative to The relationship of another unit or feature.
- the terms of relative spatial position may be intended to include different orientations of the device in use or operation other than those shown in the figures. For example, if the device in the figure is turned over, the unit described as being “below” or “beneath” other units or features will be “above” the other units or features. Therefore, the exemplary term “below” can encompass both the above and below orientations.
- the device can be oriented in other ways (rotated by 90 degrees or other orientations), and the space-related descriptors used herein are explained accordingly.
- an element or layer When an element or layer is referred to as being “on” or “connected” to another component or layer, it can be directly on, connected to, or connected to the other component or layer, or There may be intermediate elements or layers.
- this embodiment provides a mode spot converter having a first end face a optically coupled with an external optical fiber and a second end face b optically coupled with an external optical device.
- the mode spot converter includes a first The thickness of the optical waveguide 10 and the second optical waveguide 20, the thickness of the first optical waveguide 10 is smaller than the thickness of the second optical waveguide 20.
- the first optical waveguide 10 includes a first wedge structure 11 and a second wedge structure 12, the tip of the first wedge structure 11 is adjacent to the first end face a, and the tip of the second wedge structure 12 faces the same The opposite direction of the tip.
- the tip of the first wedge-shaped structure 11 is adjacent to the first end surface a, which means that the tip of the first wedge-shaped structure is closer to the first end surface a than its larger end. The meaning of being closer and closer will not be repeated here.
- a section of linear structure is also provided between the first wedge structure 11 and the second wedge structure 12, and the first wedge structure 11 and the second wedge structure 12 are connected through the linear structure in the middle.
- the first wedge structure 11 and the second wedge structure 12 are connected.
- a wedge structure 11 and a second wedge structure 12 can also be directly connected to each other.
- the second optical waveguide 20 includes a third wedge structure 21, and the tip of the third wedge structure 21 is adjacent to the first wedge structure 11.
- the third wedge structure 21 at least partially overlaps the second wedge structure 12 of the first optical waveguide 10 to adiabatically couple the optical mode in the second wedge structure 12 into the third wedge structure 21.
- the light mode in the second wedge structure 12 is adiabatically coupled to the third wedge structure 21, which means that the length of the second wedge structure 12 and the third wedge structure 21 and the overlap between them are appropriately designed. The length of, so that there is no sudden change in the mode of the light coupling between the two, the mode conversion approximately satisfies the adiabatic condition, there is no radiation loss, and the connection loss caused by the mode mismatch is small.
- the second optical waveguide 20 further includes a linear structure 22, which is adjacent to the second end surface b of the mode spot converter, and is provided between the third wedge structure 21 and the second end surface b, for communication with Waveguide optical coupling of external optical devices.
- the linear structure 22 can be designed as a multi-mode optical waveguide or a single-mode optical waveguide according to the needs of use. In other embodiments, the linear structure 22 may not be needed, and the wider end of the third wedge structure 21 is adjacent to the second end surface of the mode spot converter, and is directly optically coupled with the waveguide of the external optical device.
- the mode spot converter is provided on a silicon on insulator (SOI).
- SOI silicon on insulator
- the SOI includes a substrate 31 and a lower cladding layer 32 provided on the substrate 31, a first optical waveguide 10 and a second
- the optical waveguide 20 is provided on the lower cladding layer 32.
- an intermediate cladding layer 33 is further provided between the first optical waveguide 10 and the second optical waveguide 20.
- the refractive index of the intermediate cladding layer 33 is smaller than the refractive index of the first optical waveguide 10 and the second optical waveguide 20.
- the thickness of the cladding layer 33 is less than or equal to 3 micrometers, so that light can be gradually coupled from the first optical waveguide 10 into the second optical waveguide 20 or gradually coupled from the second optical waveguide 20 into the first optical waveguide 10.
- An upper cladding layer 34 may also be provided on the first optical waveguide 10 and the second optical waveguide 20.
- the substrate 31 is silicon
- the lower cladding layer 32 is used as an insulator layer
- silicon dioxide is used.
- the middle cladding layer 33 and the upper cladding layer 34 also use silicon dioxide.
- the first optical waveguide 10 is a silicon waveguide
- the second optical waveguide 20 is a silicon nitride waveguide
- the silicon waveguide (first optical waveguide 10) is located above the lower cladding layer 32
- the silicon nitride waveguide (second optical waveguide 20) is located on the silicon waveguide Above.
- the thickness of the first optical waveguide 10 is in the range of 60 ⁇ 200nm. It is a thin silicon optical waveguide formed by photolithography of the top layer of conventional silicon-on-insulator.
- the width of the tip cross section of the first wedge structure 11 is less than or equal to 200nm. , Has a very small tip section, so that the light mode at this section is distributed into the cladding layer, and it is more matched with the light mode transmitted by the externally coupled fiber. That is, the light field distribution at the tip and the light field distribution in the fiber have Better coincidence and higher coupling efficiency.
- the thickness of the second optical waveguide 20 is in the range of 200-800 nm, which is consistent with the thickness of the conventional silicon nitride waveguide, and the width of the tip cross section of the third wedge-shaped structure 21 is in the range of 100-300 nm.
- the overlapping portion of the first optical waveguide 10 and the second optical waveguide 20 is gradually narrowed laterally, while the third wedge-shaped structure 21 of the second optical waveguide 20 Then the light is gradually widened in the lateral direction, so that the light field transmitted in the first optical waveguide 10 is slowly released into the second optical waveguide 20, so that there is no mode mutation during the light coupling between the two, and the mode conversion approximately satisfies the adiabatic condition. That is, both TE polarized and TM polarized light can be better coupled into the second optical waveguide, which reduces the polarization-related loss and improves the coupling efficiency.
- the difference from Embodiment 1 is that the second optical waveguide 20 of the mode spot converter in this embodiment adds an edge coupling structure 23.
- One end of the edge coupling structure 23 is connected to the tip of the third wedge structure 21. Connected, the other end deviates from the central axis of the second optical waveguide 20 and extends toward the edge of the first optical waveguide 10 to better adiabaticly couple the optical mode in the first optical waveguide 10 to the second optical waveguide 20.
- the tip size of the third wedge structure 21 of the second optical waveguide 20 needs to be adjusted.
- the tip of the third wedge structure 21 cannot be infinitely small. Therefore, in order to further reduce the polarization-related loss and improve the coupling efficiency, the mode spot converter of this embodiment is The edge coupling structure 23 described above is added to the tip of the third wedge structure 21.
- the end of the side coupling structure 23 away from the third wedge structure 21 extends from the edge of the first optical waveguide 10, and the distance between the end surface and the edge of the first optical waveguide 10 needs to be large enough to prevent transmission in the first optical waveguide 10. It is advisable for the light to enter the edge coupling structure 23 from this end surface.
- the cross-sectional width of the end of the edge coupling structure 23 away from the third wedge structure 21 is less than or equal to 200 nm.
- the simulation test is carried out with the following size structure, the thickness H1 of the first optical waveguide 10 is 110 nm, the thickness H2 of the second optical waveguide 20 is 400 nm, and the distance between the first optical waveguide 10 and the second optical waveguide 20
- the thickness H3 of the intermediate cladding layer is 190nm.
- the end face width D1 of the edge coupling structure at E is 100 nm
- the center distance D5 between the edge coupling structure 23 and the first optical waveguide 10 at E is 2 ⁇ m
- the tip width D2 of the third wedge structure 21 of the second optical waveguide 20 at B is 100 nm
- the length of the BE section is 40 ⁇ m
- the tip width D4 of the second wedge structure 12 of the first optical waveguide 10 at C is 100 nm
- the width D3 of the linear structure 22 of the second optical waveguide 20 is 800 nm
- the length of the BC section is 40 ⁇ m.
- the polarization-dependent loss of light coupling between the first optical waveguide 10 and the second optical waveguide 20 is shown in Figure 6.
- the loss of the TE polarization mode is less than 0.05dB.
- the loss of the TM polarization mode is less than 0.25dB.
- the polarization-related loss is reduced by more than 87.5%, which greatly improves the coupling. efficient.
- the first end face a of the mode spot converter in this embodiment is provided with a trench under the first optical waveguide 10 near the substrate 31 of the lower cladding layer 32.
- the hollow 40 may be etched on the end face a of the substrate 31 by a wet etching process to confine the light beam in the upper cladding layer 34, the lower cladding layer 32 and the first optical waveguide 10 to avoid The light coupled from the external optical fiber to the first optical waveguide 10 enters the substrate 31 and is radiated away from the substrate, thereby further improving the coupling efficiency between the external optical fiber and the mode spot converter.
- this embodiment provides a silicon optical integrated chip, which includes a substrate 31, a lower cladding layer 32, a top layer of silicon, a silicon nitride layer, and an upper cladding layer 34.
- an optical active device 60 such as a photodetector, is provided on the top silicon
- a silicon nitride optical waveguide 50 is provided on the silicon nitride layer.
- the figure shows only a part of the silicon optical integrated chip, which simply shows a cross-sectional schematic diagram of a silicon nitride optical waveguide 50.
- the silicon nitride layer on the silicon optical integrated chip can be designed with several silicon nitride optical waveguides according to actual needs.
- Optical passive components such as wavelength division multiplexer or coupler.
- the mode spot converter of any one of the above-mentioned embodiments 1-3 is provided near the end face where the silicon optical integrated chip is coupled with the external optical fiber 70.
- the thickness of the second optical waveguide 20 of the mode spot converter and the silicon nitride layer The thickness is the same, and is connected to the silicon nitride optical waveguide 50 of the silicon optical integrated chip.
- the top layer of silicon near the external optical fiber is thinned into a thin silicon waveguide (first optical waveguide 10), which has a better matching degree with the optical field of the external optical fiber 70.
- the optical signal output by the external optical fiber 70 is coupled to the second optical waveguide 20 through the first optical waveguide 10 of the mode spot converter and transmitted into the silicon nitride optical waveguide 50, and is coupled to the light on the top silicon via the silicon nitride optical waveguide 50.
- Active device 60 within.
- the optical active device 60 may also be an optical modulator, and the output modulated optical signal is transmitted to the second optical waveguide 20 of the mode spot converter through the silicon nitride optical waveguide 50. After being coupled to the first optical waveguide 10 via the second optical waveguide 20, the first optical waveguide 10 is coupled to the external optical fiber 70, and the external optical fiber 70 outputs an optical signal.
- the silicon optical integrated chip in this embodiment uses silicon nitride as an optical waveguide for optical transmission, which has better thermal stability and lower transmission loss, and uses the mode spot converter and external optical fiber in any of the above embodiments. For coupling, it has a higher mode matching degree and coupling efficiency with the optical fiber, and at the same time has a lower polarization-related loss.
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Abstract
A spot size converter and a silicon-optical integrated chip. The spot size converter is provided with a first end face (a) optically coupled to an external optical fiber (70) and a second end face (b) optically coupled to an external optical device, and comprises a first optical waveguide (10) and a second optical waveguide (20), the first optical waveguide (10) comprising a first wedge-shaped structure (11) and a second wedge-shaped structure (12), the first wedge-shaped structure (11) and the second wedge-shaped structure (12) facing opposite directions, and the second optical waveguide (20) comprising a third wedge-shaped structure (21), a tip of the third wedge-shaped structure (21) facing the first wedge-shaped structure (11) and at least partially overlapping with the second wedge-shaped structure (12). By designing a special waveguide coupling structure, the mode matching degree between the spot size converter and the external optical fiber (70) is improved, the polarization-dependent loss between the two optical waveguides in the spot size converter is reduced, and the thermal stability of optical waveguides in the silicon-optical integrated chip is improved, thereby reducing the light transmission loss in the silicon-optical integrated chip.
Description
本申请涉及光通信技术领域,尤其涉及一种模斑变换器及硅光集成芯片。This application relates to the field of optical communication technology, and in particular to a mode spot converter and a silicon optical integrated chip.
硅光芯片是实现光互连的关键技术,能够有效降低光通信中模块的成本。但是在光纤与硅光芯片的耦合处,典型单模硅波导的尺寸为420nm×220nm,而单模光纤的尺寸在9μm左右,二者直接耦合的耦合效率太低,需要有特殊的器件实现两者之间的高效耦合。目前通用的耦合方案有光栅耦合器的垂直耦合方式和模斑变换器(Spot Size Converter,SSC)的水平耦合方式。光栅耦合器是通过在硅波导上制作光栅结构,当光从光纤入射到光栅耦合器表面时,通过布拉格衍射效应实现与芯片上方摆放的光纤进行有效的耦合。这种方式可以提高光纤与耦合器的对准容差,但耦合效率较低且对波长敏感,不利于封装,多被用来测试芯片。所以在产品中多采用模斑变换器进行水平耦合,耦合效率高。Silicon optical chip is a key technology to realize optical interconnection, which can effectively reduce the cost of modules in optical communication. However, at the coupling of optical fiber and silicon optical chip, the size of a typical single-mode silicon waveguide is 420nm×220nm, while the size of a single-mode fiber is about 9μm. The coupling efficiency of the direct coupling between the two is too low, and special devices are required to achieve the two Efficient coupling between participants. The current common coupling schemes include the vertical coupling mode of the grating coupler and the horizontal coupling mode of the spot size converter (Spot Size Converter, SSC). The grating coupler is made by fabricating a grating structure on a silicon waveguide. When light is incident on the surface of the grating coupler from an optical fiber, it achieves effective coupling with the optical fiber placed above the chip through the Bragg diffraction effect. This method can improve the alignment tolerance between the optical fiber and the coupler, but the coupling efficiency is low and the wavelength is sensitive, which is not conducive to packaging, and is often used to test chips. Therefore, the mode spot converter is often used for horizontal coupling in the product, and the coupling efficiency is high.
为了提高模斑变换器与单模光纤的模式匹配度,已有文献提出了多种不同结构的模斑变换器,其中与单模光纤具有较好模式匹配的结构,如图1所示的双层阶梯结构的模斑变换器,包括不同厚度的两个芯层:第一芯层10’和第二芯层20’,第一芯层10’包括第一楔形结构11’和第一线性结构12’,第二芯层20’包括第二楔形结构21’和第二线性结构22’,第二楔形结构21’与第一线性结构12’形成阶梯楔形结构。第一芯层10’的厚度比较薄,其第一楔形结构11’的尖端与外部光纤耦合,在第一楔形结构11’的尖端处的光场分布与光纤中的光场分布具有更好的重合度、更高的耦合效率。第一楔形结构11’横向展宽到第一线性结构12’处,第二芯层20’的厚度需要与外部硅光器件的顶层硅的厚度一致,比第一芯层10’厚,通过第二楔形结构21’与第一线性结构12’耦合实现光模式从第一芯层10’到第二芯层20’的变换。但是楔形结构的尖端受半导体加工工艺的限制,尺寸很难做到无限小,容易引入偏振相关损耗,即光从较薄厚度的波导向正常厚度波导渐变过程中,水平偏振模式(TE模)光损耗较小,垂直偏振的模式(TM模)光损耗较大,整体的模斑变换器具有较大的偏振相关损耗。In order to improve the mode matching degree between the mode spot converter and the single-mode fiber, the existing literature has proposed a variety of different structure of the mode spot converter, which has a better mode matching structure with the single-mode fiber, as shown in Figure 1. The mode spot converter of the layer ladder structure includes two core layers with different thicknesses: a first core layer 10' and a second core layer 20'. The first core layer 10' includes a first wedge structure 11' and a first linear structure 12', the second core layer 20' includes a second wedge structure 21' and a second linear structure 22', and the second wedge structure 21' and the first linear structure 12' form a stepped wedge structure. The thickness of the first core layer 10' is relatively thin, and the tip of the first wedge structure 11' is coupled to the external optical fiber, and the optical field distribution at the tip of the first wedge structure 11' is better than the optical field distribution in the optical fiber. Coincidence, higher coupling efficiency. The first wedge-shaped structure 11' is laterally widened to the first linear structure 12'. The thickness of the second core layer 20' needs to be consistent with the thickness of the top silicon of the external silicon optical device, which is thicker than the first core layer 10'. The wedge structure 21' is coupled with the first linear structure 12' to realize the transformation of the light mode from the first core layer 10' to the second core layer 20'. However, the tip of the wedge-shaped structure is limited by the semiconductor processing technology, and the size is difficult to be infinitely small, and it is easy to introduce polarization-dependent loss, that is, the light in the horizontal polarization mode (TE mode) is gradual from the thinner-thickness waveguide to the normal-thickness waveguide. The loss is small, and the optical loss in the vertical polarization mode (TM mode) is large, and the overall mode spot converter has a large polarization-dependent loss.
上述模斑变换器的第一楔形结构和第二楔形结构的尖端横截面宽度都为100nm时,从第一芯层耦合到第二芯层时的偏振相关损耗如图2所示,对于TE模,该楔形结构的损耗较小,但是对于TM模,楔形结构的损耗较大,引入了较大的偏振相关损耗。When the first wedge structure and the second wedge structure of the above-mentioned mode spot converter have a tip cross-sectional width of 100 nm, the polarization-dependent loss when coupling from the first core layer to the second core layer is shown in Fig. 2. For the TE mode , The wedge-shaped structure has a small loss, but for the TM mode, the wedge-shaped structure has a large loss, which introduces a large polarization-dependent loss.
本申请的目的在于提供一种模斑变换器及硅光集成芯片,具有极小的偏振相关损耗、更高的耦合效率和更好的热稳定性。The purpose of the present application is to provide a mode spot converter and a silicon-optical integrated chip, which has extremely small polarization-related loss, higher coupling efficiency and better thermal stability.
为了实现上述目的之一,本申请提供了一种模斑变换器,具有与外部光纤光耦合的第一端面和与外部光器件光耦合的第二端面,其特征在于,所述模斑变换器包括:In order to achieve one of the above objectives, the present application provides a mode spot converter having a first end face optically coupled with an external optical fiber and a second end face optically coupled with an external optical device, characterized in that the mode spot converter include:
第一光波导,包括第一楔形结构和第二楔形结构,所述第一楔形结构的尖端临近所述第一端面,所述第二楔形结构的尖端朝向与所述第一楔形结构的尖端相背的方向;The first optical waveguide includes a first wedge structure and a second wedge structure, the tip of the first wedge structure is adjacent to the first end surface, and the tip of the second wedge structure faces the same as the tip of the first wedge structure Back direction
第二光波导,包括第三楔形结构,所述第三楔形结构与所述第二楔形结构至少部分重叠以将所述第二楔形结构中的光模式绝热地耦合到所述第三楔形结构中;所述第三楔形结构的尖端朝向所述第一楔形结构。The second optical waveguide includes a third wedge-shaped structure that at least partially overlaps the second wedge-shaped structure to adiabatically couple the optical mode in the second wedge-shaped structure into the third wedge-shaped structure ; The tip of the third wedge-shaped structure faces the first wedge-shaped structure.
作为实施方式的进一步改进,所述模斑变换器还包括衬底和设于所述衬底上的下包层,所述第一光波导和第二光波导设于所述下包层上。As a further improvement of the embodiment, the mode spot converter further includes a substrate and a lower cladding layer provided on the substrate, and the first optical waveguide and the second optical waveguide are provided on the lower cladding layer.
作为实施方式的进一步改进,所述第一光波导和第二光波导之间还设有中间包层,所述中间包层的折射率小于所述第一光波导和第二光波导的折射率。As a further improvement of the embodiment, an intermediate cladding layer is further provided between the first optical waveguide and the second optical waveguide, and the refractive index of the intermediate cladding layer is smaller than the refractive index of the first optical waveguide and the second optical waveguide. .
作为实施方式的进一步改进,所述中间包层的厚度小于或等于3微米。As a further improvement of the embodiment, the thickness of the intermediate cladding layer is less than or equal to 3 microns.
作为实施方式的进一步改进,所述第一端面在所述第一光波导下方临近所述下包层的衬底处设有挖空部。As a further improvement of the embodiment, the first end surface is provided with a hollow portion below the first optical waveguide near the substrate of the undercladding layer.
作为实施方式的进一步改进,所述第一光波导为硅波导,所述第二光波导为氮化硅波导,所述硅波导位于所述下包层上方,所述氮化硅波导位于所述硅波导上方。As a further improvement of the embodiment, the first optical waveguide is a silicon waveguide, the second optical waveguide is a silicon nitride waveguide, the silicon waveguide is located above the under-cladding layer, and the silicon nitride waveguide is located on the Above the silicon waveguide.
作为实施方式的进一步改进,所述第一光波导的厚度小于或等于所述第二光波导的厚度。As a further improvement of the embodiment, the thickness of the first optical waveguide is less than or equal to the thickness of the second optical waveguide.
作为实施方式的进一步改进,所述第一光波导的厚度在60~200nm范围内,所述第二光波导的厚度在200~800nm的范围内。As a further improvement of the embodiment, the thickness of the first optical waveguide is in the range of 60-200 nm, and the thickness of the second optical waveguide is in the range of 200-800 nm.
作为实施方式的进一步改进,所述第一楔形结构的尖端横截面的宽度小于或等于200nm;所述第三楔形结构的尖端横截面的宽度在100nm~300nm范围内。As a further improvement of the embodiment, the width of the tip cross section of the first wedge structure is less than or equal to 200 nm; the width of the tip cross section of the third wedge structure is in the range of 100 nm to 300 nm.
作为实施方式的进一步改进,所述第二光波导还包括边耦合结构,所述边耦合结构一端与所述第三楔形结构的尖端连接,另一端偏离所述第二光波导的中心轴线向所述第一光波导的边缘延伸以将所述第一光波导中的光模式绝热地耦合到所述第二光波导中。As a further improvement of the embodiment, the second optical waveguide further includes an edge coupling structure, one end of the edge coupling structure is connected to the tip of the third wedge structure, and the other end is deviated from the central axis of the second optical waveguide. The edge of the first optical waveguide extends to adiabatically couple the optical mode in the first optical waveguide into the second optical waveguide.
作为实施方式的进一步改进,所述边耦合结构远离所述第三楔形结构的一端的横截面宽度小于或等于200nm。As a further improvement of the embodiment, the cross-sectional width of one end of the edge coupling structure away from the third wedge structure is less than or equal to 200 nm.
作为实施方式的进一步改进,所述边耦合结构远离所述第三楔形结构的一端延伸出所述第一光波导边缘。As a further improvement of the embodiment, an end of the edge coupling structure away from the third wedge structure extends out of the edge of the first optical waveguide.
作为实施方式的进一步改进,所述第二光波导还包括线性结构,所述线性结构设于所述第三楔形结构与所述第二端面之间。As a further improvement of the embodiment, the second optical waveguide further includes a linear structure, and the linear structure is provided between the third wedge-shaped structure and the second end surface.
本申请还提供了一种硅光集成芯片,包括衬底、下包层、顶层硅、氮化硅层和上包层;所述顶层硅上设有光有源器件,所述氮化硅层设有氮化硅光波导;The application also provides a silicon optical integrated chip, including a substrate, a lower cladding layer, a top layer of silicon, a silicon nitride layer, and an upper cladding layer; the top layer of silicon is provided with an optically active device, and the silicon nitride layer Equipped with silicon nitride optical waveguide;
所述硅光集成芯片上临近所述硅光集成芯片与外部光纤的耦合端面设有上述任一实施例的模斑变换器;The mode spot converter of any one of the above-mentioned embodiments is provided on the silicon optical integrated chip adjacent to the coupling end surface of the silicon optical integrated chip and the external optical fiber;
所述外部光纤输出的光信号经所述模斑变换器的第一光波导耦合到所述第二光波导并传输到所述氮化硅光波导内,经所述氮化硅光波导耦合到所述顶层硅上的光有源器件内。The optical signal output by the external optical fiber is coupled to the second optical waveguide via the first optical waveguide of the mode spot converter and transmitted into the silicon nitride optical waveguide, and is coupled to the silicon nitride optical waveguide via the silicon nitride optical waveguide. Inside the photoactive device on the top layer of silicon.
通过设计特殊的波导耦合结构提高模斑变换器与外部光纤的模式匹配度,减小模斑变换器内两个光波导之间的偏振相关损耗,提高硅光集成芯片内光波导的热稳定性,从而降低硅光集成芯片内的光传输损耗。By designing a special waveguide coupling structure, the mode matching degree between the mode spot converter and the external fiber is improved, the polarization-related loss between the two optical waveguides in the mode spot converter is reduced, and the thermal stability of the optical waveguide in the silicon optical integrated chip is improved. , Thereby reducing the optical transmission loss in the silicon optical integrated chip.
图1为现有技术的模斑变换器结构及截面示意图;FIG. 1 is a schematic diagram of the structure and cross-sectional view of a mode spot converter in the prior art;
图2为图1中模斑变换器的模式变换耦合的偏振相关损耗示意图;2 is a schematic diagram of polarization dependent loss of mode conversion coupling of the mode spot converter in FIG. 1;
图3为本申请实施例1的模斑变换器结构及截面示意图;FIG. 3 is a schematic diagram of the structure and cross-section of the mode spot converter according to Embodiment 1 of the application; FIG.
图4为图3中模斑变换器沿中心轴的纵截面示意图;4 is a schematic longitudinal cross-sectional view of the mode spot converter in FIG. 3 along the central axis;
图5为本申请实施例2的模斑变换器结构及截面示意图;5 is a schematic diagram of the structure and cross-sectional view of the mode spot converter according to Embodiment 2 of the application;
图6为图5中模斑变换器的模式变换耦合的偏振相关损耗示意图;6 is a schematic diagram of the polarization dependent loss of the mode conversion coupling of the mode spot converter in FIG. 5;
图7为本申请实施例3的模斑变换器纵截面及端面示意图;FIG. 7 is a schematic diagram of a longitudinal section and an end face of the mode spot converter according to Embodiment 3 of the application;
图8为本申请实施例4的硅光集成芯片部分示意图。FIG. 8 is a partial schematic diagram of a silicon optical integrated chip according to Embodiment 4 of the application.
以下将结合附图所示的具体实施方式对本申请进行详细描述。但这些实施方式并不限制本申请,本领域的普通技术人员根据这些实施方式所做出的结构、方法、或功能上的变换均包含在本申请的保护范围内。The application will be described in detail below in conjunction with the specific implementations shown in the drawings. However, these embodiments do not limit the application, and the structural, method, or functional transformations made by those of ordinary skill in the art according to these embodiments are all included in the protection scope of the application.
在本申请的各个图示中,为了便于图示,结构或部分的某些尺寸会相对于其它结构或部分夸大,因此,仅用于图示本申请的主题的基本结构。In the drawings of the present application, for the convenience of illustration, some dimensions of the structure or part are exaggerated relative to other structures or parts, and therefore, they are only used to illustrate the basic structure of the subject matter of the present application.
另外,本文使用的例如“上”、“上方”、“下”、“下方”等表示空间相对位置的术语是出于便于说明的目的来描述如附图中所示的一个单元或特征相对于另一个单元或特征的关系。空间相对位置的术语可以旨在包括设备在使用或工作中除了图中所示方位以外的不同方位。例如,如果将图中的设备翻转,则被描述为位于其他单元或特征“下方”或“之下”的单元将位于其他单元或特征“上方”。因此,示例性术语“下方”可以囊括上方和下方这两种方位。设备可以以其他方式被定向(旋转90度或其他朝向),并相应地解释本文使用的与空间相关的描述语。当元件或层被称为在另一部件或层“上”、与另一部件或层“连接”时,其可以直接在该另一部件或层上、连接到该另一部件或层,或者可以存在中间元件或层。In addition, terms such as "upper", "above", "below", "below" and the like used herein to indicate a relative position in space are for the purpose of facilitating explanation to describe a unit or feature as shown in the drawings relative to The relationship of another unit or feature. The terms of relative spatial position may be intended to include different orientations of the device in use or operation other than those shown in the figures. For example, if the device in the figure is turned over, the unit described as being "below" or "beneath" other units or features will be "above" the other units or features. Therefore, the exemplary term "below" can encompass both the above and below orientations. The device can be oriented in other ways (rotated by 90 degrees or other orientations), and the space-related descriptors used herein are explained accordingly. When an element or layer is referred to as being “on” or “connected” to another component or layer, it can be directly on, connected to, or connected to the other component or layer, or There may be intermediate elements or layers.
实施例1Example 1
如图3和4,该实施例提供了一种模斑变换器,具有与外部光纤光耦合的第一端面a和与外部光器件光耦合的第二端面b,该模斑变换器包括第一光波导10和第二光波导20,第一光波导10的厚度小于第二光波导20的厚度。其中,第一光波导10包括第一楔形结构11和第二楔形结构12,该第一楔形结构11的尖端临近上述第一端面a,第二楔形结构12的尖端朝向与第一楔形结构11的尖端相背的方向。这里,该第一楔形结构11的尖端临近上述第一端面a,指的是第一楔形结构的尖端与其较大的一端相比更靠近第一端面a,下文中的“临近”同样指的更靠近、更接近的意思,不再赘述。该实施例中,第一楔形结构11和第二楔形结构12之间还设有一段线性结构,通过中间的线性结构连接第一楔形结构11和第二楔形结构12,在其它实施例中,第一楔形结构11和第二楔形结构12也可以直接相互连接。第二光波导20包括第三楔形结构21,该第三楔形结构21的尖端临近上述第一楔形结构11。第三楔形结构21与第一光波导10的第二楔形结构12至少部分重叠以将第二楔形结构12中的光模式绝热地耦合到第三楔形结构21中。这里,第二楔形结构12中的光模式绝热地耦合到第三楔形结构21中,指的是通过设计合适的第二楔形结构12和第三楔形结构21的长度以及二者之间重叠的部分的长度,使光在二者之间耦合的过程中没有模式突变,模式变换近似满足绝热条件,无辐射损耗,模式失配引起的连接损耗较小。该实施例中,第二光波导20还包括一线性结构22,该线性结构22临近模斑变换器的第二端面b,设于第三楔形结构21与第二端面b之间,用于与外部光器件的波导光耦合。该线性结构22可根据使用需要设计成多模光波导或单模光波导。在其它实施例中,也可以不需要线性结构22,第三楔形结构21的较宽的一端临近模斑变换器的第二端面,直接与外部光器件的波导光耦合。As shown in Figures 3 and 4, this embodiment provides a mode spot converter having a first end face a optically coupled with an external optical fiber and a second end face b optically coupled with an external optical device. The mode spot converter includes a first The thickness of the optical waveguide 10 and the second optical waveguide 20, the thickness of the first optical waveguide 10 is smaller than the thickness of the second optical waveguide 20. The first optical waveguide 10 includes a first wedge structure 11 and a second wedge structure 12, the tip of the first wedge structure 11 is adjacent to the first end face a, and the tip of the second wedge structure 12 faces the same The opposite direction of the tip. Here, the tip of the first wedge-shaped structure 11 is adjacent to the first end surface a, which means that the tip of the first wedge-shaped structure is closer to the first end surface a than its larger end. The meaning of being closer and closer will not be repeated here. In this embodiment, a section of linear structure is also provided between the first wedge structure 11 and the second wedge structure 12, and the first wedge structure 11 and the second wedge structure 12 are connected through the linear structure in the middle. In other embodiments, the first wedge structure 11 and the second wedge structure 12 are connected. A wedge structure 11 and a second wedge structure 12 can also be directly connected to each other. The second optical waveguide 20 includes a third wedge structure 21, and the tip of the third wedge structure 21 is adjacent to the first wedge structure 11. The third wedge structure 21 at least partially overlaps the second wedge structure 12 of the first optical waveguide 10 to adiabatically couple the optical mode in the second wedge structure 12 into the third wedge structure 21. Here, the light mode in the second wedge structure 12 is adiabatically coupled to the third wedge structure 21, which means that the length of the second wedge structure 12 and the third wedge structure 21 and the overlap between them are appropriately designed. The length of, so that there is no sudden change in the mode of the light coupling between the two, the mode conversion approximately satisfies the adiabatic condition, there is no radiation loss, and the connection loss caused by the mode mismatch is small. In this embodiment, the second optical waveguide 20 further includes a linear structure 22, which is adjacent to the second end surface b of the mode spot converter, and is provided between the third wedge structure 21 and the second end surface b, for communication with Waveguide optical coupling of external optical devices. The linear structure 22 can be designed as a multi-mode optical waveguide or a single-mode optical waveguide according to the needs of use. In other embodiments, the linear structure 22 may not be needed, and the wider end of the third wedge structure 21 is adjacent to the second end surface of the mode spot converter, and is directly optically coupled with the waveguide of the external optical device.
该实施例中,模斑变换器设在绝缘体上硅(Silicon on Insulator,SOI)上,该SOI包括衬底31和设于衬底31上的下包层32,第一光波导10和第二光波导20设于下包层32上。该实施例中,第一光波导10和第二光波导20之间还设有中间包层33,中间包层33的折射率小于第一光波导10和第二光波导20的折射率,中间包层33的厚度小于或等于3微米,使得光可以从第一光波导10逐渐耦合到第二光波导20中,或者从第二光波导20逐渐耦合到第一光波导10中。在第一光波导10和第二光波导20上面还可以设有上包层34。In this embodiment, the mode spot converter is provided on a silicon on insulator (SOI). The SOI includes a substrate 31 and a lower cladding layer 32 provided on the substrate 31, a first optical waveguide 10 and a second The optical waveguide 20 is provided on the lower cladding layer 32. In this embodiment, an intermediate cladding layer 33 is further provided between the first optical waveguide 10 and the second optical waveguide 20. The refractive index of the intermediate cladding layer 33 is smaller than the refractive index of the first optical waveguide 10 and the second optical waveguide 20. The thickness of the cladding layer 33 is less than or equal to 3 micrometers, so that light can be gradually coupled from the first optical waveguide 10 into the second optical waveguide 20 or gradually coupled from the second optical waveguide 20 into the first optical waveguide 10. An upper cladding layer 34 may also be provided on the first optical waveguide 10 and the second optical waveguide 20.
这里,衬底31为硅,下包层32作为绝缘体层,采用的是二氧化硅,中间包层33和上包层34也都采用二氧化硅。第一光波导10为硅波导,第二光波导20为氮化硅波导,硅波导(第一光波导10)位于下包层32上方,氮化硅波导(第二光波导20)位于硅波导上方。第一光波导10的厚度在60~200nm范围内,是通过将常规的绝缘体上硅的顶层硅光刻削薄形成的薄硅光波导,其第一楔形结构11的尖端横截面的宽度小于或等于200nm,具有极小的尖端截面,从而使得该截面处的光模式分布到包层里,与外部耦合的光纤传输的光模式更加匹配,即该尖端处的光场分布与光纤中的光场分布具有更好的重合度和更高的耦合效率。而第二光波导20的厚度在200~800nm的范围内,与常规的氮化硅波导厚度一致,其第三楔形结构21的尖端横截面的宽度在100nm~300nm范围内。光在第一光波导10和第二光波导20之间耦合的时候由于光波导截面的不同,使得光的传输模式会有一个突变,从而引起损耗以及偏振相关损耗,所以该实施例在第一光波导10和第二光波导20的耦合处设计了特殊的结构来降低损耗及偏振相关损耗。该实施例中,通过设计第一光波导10的第二楔形结构12使第一光波导10与第二光波导20重叠的部分横向逐渐收窄,而第二光波导20的第三楔形结构21则横向逐渐展宽,从而将第一光波导10中传输的光场慢慢释放到第二光波导20中,使光在二者之间耦合的过程中没有模式突变,模式变换近似满足绝热条件,即TE偏振和TM偏振的光均能较好地耦合到第二光波导中,降低了偏振相关损耗,提高了耦合效率。Here, the substrate 31 is silicon, the lower cladding layer 32 is used as an insulator layer, and silicon dioxide is used. The middle cladding layer 33 and the upper cladding layer 34 also use silicon dioxide. The first optical waveguide 10 is a silicon waveguide, the second optical waveguide 20 is a silicon nitride waveguide, the silicon waveguide (first optical waveguide 10) is located above the lower cladding layer 32, and the silicon nitride waveguide (second optical waveguide 20) is located on the silicon waveguide Above. The thickness of the first optical waveguide 10 is in the range of 60~200nm. It is a thin silicon optical waveguide formed by photolithography of the top layer of conventional silicon-on-insulator. The width of the tip cross section of the first wedge structure 11 is less than or equal to 200nm. , Has a very small tip section, so that the light mode at this section is distributed into the cladding layer, and it is more matched with the light mode transmitted by the externally coupled fiber. That is, the light field distribution at the tip and the light field distribution in the fiber have Better coincidence and higher coupling efficiency. The thickness of the second optical waveguide 20 is in the range of 200-800 nm, which is consistent with the thickness of the conventional silicon nitride waveguide, and the width of the tip cross section of the third wedge-shaped structure 21 is in the range of 100-300 nm. When light is coupled between the first optical waveguide 10 and the second optical waveguide 20, due to the difference in the cross-section of the optical waveguide, there will be a sudden change in the transmission mode of the light, which will cause loss and polarization-dependent loss. Therefore, this embodiment is described in the first A special structure is designed at the coupling of the optical waveguide 10 and the second optical waveguide 20 to reduce loss and polarization-dependent loss. In this embodiment, by designing the second wedge-shaped structure 12 of the first optical waveguide 10, the overlapping portion of the first optical waveguide 10 and the second optical waveguide 20 is gradually narrowed laterally, while the third wedge-shaped structure 21 of the second optical waveguide 20 Then the light is gradually widened in the lateral direction, so that the light field transmitted in the first optical waveguide 10 is slowly released into the second optical waveguide 20, so that there is no mode mutation during the light coupling between the two, and the mode conversion approximately satisfies the adiabatic condition. That is, both TE polarized and TM polarized light can be better coupled into the second optical waveguide, which reduces the polarization-related loss and improves the coupling efficiency.
实施例2Example 2
如图5所示,与实施例1不同的是,该实施例中的模斑变换器的第二光波导20增加了边耦合结构23,该边耦合结构23一端与第三楔形结构21的尖端连接,另一端偏离第二光波导20的中心轴线向第一光波导10的边缘延伸以更好地将第一光波导10中的光模式绝热地耦合到第二光波导20中。As shown in FIG. 5, the difference from Embodiment 1 is that the second optical waveguide 20 of the mode spot converter in this embodiment adds an edge coupling structure 23. One end of the edge coupling structure 23 is connected to the tip of the third wedge structure 21. Connected, the other end deviates from the central axis of the second optical waveguide 20 and extends toward the edge of the first optical waveguide 10 to better adiabaticly couple the optical mode in the first optical waveguide 10 to the second optical waveguide 20.
在实施例1的模斑变换器中,为了尽可能地降低第一光波导10和第二光波导20之间的偏振相关损耗,第二光波导20的第三楔形结构21的尖端尺寸需要做到尽量地小,但是受半导体加工工艺限制,该第三楔形结构21的尖端没办法做到无限小,所以为了更进一步地降低偏振相关损耗,提高耦合效率,该实施例的模斑变换器在第三楔形结构21的尖端处增加了上述边耦合结构23。该边耦合结构23远离第三楔形结构21的一端延伸出第一光波导10边缘,该端面与第一光波导10的边缘之间的间距需要足够大,以足以阻止第一光波导10内传输的光从该端面进入边耦合结构23为宜。该实施例中,边耦合结构23远离第三楔形结构21的一端的横截面宽度小于或等于200nm。In the mode spot converter of Embodiment 1, in order to reduce the polarization-dependent loss between the first optical waveguide 10 and the second optical waveguide 20 as much as possible, the tip size of the third wedge structure 21 of the second optical waveguide 20 needs to be adjusted. To be as small as possible, but limited by the semiconductor processing technology, the tip of the third wedge structure 21 cannot be infinitely small. Therefore, in order to further reduce the polarization-related loss and improve the coupling efficiency, the mode spot converter of this embodiment is The edge coupling structure 23 described above is added to the tip of the third wedge structure 21. The end of the side coupling structure 23 away from the third wedge structure 21 extends from the edge of the first optical waveguide 10, and the distance between the end surface and the edge of the first optical waveguide 10 needs to be large enough to prevent transmission in the first optical waveguide 10. It is advisable for the light to enter the edge coupling structure 23 from this end surface. In this embodiment, the cross-sectional width of the end of the edge coupling structure 23 away from the third wedge structure 21 is less than or equal to 200 nm.
如图5所示,这里以如下尺寸结构进行仿真测试,第一光波导10的厚度H1为110nm,第二光波导20的厚度H2为400nm,第一光波导10和第二光波导20之间的中间包层的厚度H3为190nm。E处边耦合结构的端面宽度D1为100nm,该E处边耦合结构23与第一光波导10的中心间距D5为2μm,B处第二光波导20第三楔形结构21的尖端宽度D2为100nm,BE段的长度为40μm;C处第一光波导10第二楔形结构12的尖端宽度D4为100nm,第二光波导20的线性结构22宽度D3为800nm,BC段的长度为40μm。该结构的模斑变换器中,光在第一光波导10和第二光波导20之间耦合的偏振相关损耗如图6所示,在1310nm波长处,TE偏振模的损耗不到0.05dB,TM偏振模的损耗不到0.25dB,与现有技术中的双层阶梯结构的模斑变换器的TM偏振模具有2dB多的损耗相比,偏振相关损耗降低了87.5%以上,大大提高了耦合效率。As shown in FIG. 5, the simulation test is carried out with the following size structure, the thickness H1 of the first optical waveguide 10 is 110 nm, the thickness H2 of the second optical waveguide 20 is 400 nm, and the distance between the first optical waveguide 10 and the second optical waveguide 20 The thickness H3 of the intermediate cladding layer is 190nm. The end face width D1 of the edge coupling structure at E is 100 nm, the center distance D5 between the edge coupling structure 23 and the first optical waveguide 10 at E is 2 μm, and the tip width D2 of the third wedge structure 21 of the second optical waveguide 20 at B is 100 nm , The length of the BE section is 40 μm; the tip width D4 of the second wedge structure 12 of the first optical waveguide 10 at C is 100 nm, the width D3 of the linear structure 22 of the second optical waveguide 20 is 800 nm, and the length of the BC section is 40 μm. In the mode spot converter of this structure, the polarization-dependent loss of light coupling between the first optical waveguide 10 and the second optical waveguide 20 is shown in Figure 6. At a wavelength of 1310nm, the loss of the TE polarization mode is less than 0.05dB. The loss of the TM polarization mode is less than 0.25dB. Compared with the 2dB loss of the TM polarization mode of the double-layer stepped mode spot converter in the prior art, the polarization-related loss is reduced by more than 87.5%, which greatly improves the coupling. efficient.
实施例3Example 3
如图7所示,与实施例1和2不同的是,该实施例中的模斑变换器的第一端面a在第一光波导10下方临近下包层32的衬底31处设有挖空部40,例如可以采用湿法刻蚀工艺在衬底31的端面a刻蚀出挖空部40,以将光束缚在上包层34、下包层32和第一光波导10内,避免从外部光纤耦合到第一光波导10的光进入衬底31从衬底辐射损耗掉,从而进一步提高了外部光纤与模斑转换器之间的耦合效率。As shown in FIG. 7, the difference from Embodiments 1 and 2 is that the first end face a of the mode spot converter in this embodiment is provided with a trench under the first optical waveguide 10 near the substrate 31 of the lower cladding layer 32. For example, the hollow 40 may be etched on the end face a of the substrate 31 by a wet etching process to confine the light beam in the upper cladding layer 34, the lower cladding layer 32 and the first optical waveguide 10 to avoid The light coupled from the external optical fiber to the first optical waveguide 10 enters the substrate 31 and is radiated away from the substrate, thereby further improving the coupling efficiency between the external optical fiber and the mode spot converter.
实施例4Example 4
如图8所示,该实施例提供了一种硅光集成芯片,该硅光集成芯片包括衬底31、下包层32、顶层硅、氮化硅层和上包层34。其中,顶层硅上设有光有源器件60,如光探测器等,氮化硅层设有氮化硅光波导50。图中仅示意了硅光集成芯片的其中一部分,简单表示出了一个氮化硅光波导50的剖面示意图,硅光集成芯片上的氮化硅层可以根据实际使用需要设计若干氮化硅光波导、波分复用器或耦合器等光无源器件。在该硅光集成芯片与外部光纤70耦合的端面临近处设有上述实施例1-3任一实施例的模斑变换器,模斑变换器的第二光波导20的厚度与氮化硅层的厚度一致,与该硅光集成芯片的氮化硅光波导50连接。临近外部光纤处的顶层硅通过减薄处理做成薄硅波导(第一光波导10),与外部光纤70的光场具有更好的匹配度。外部光纤70输出的光信号经模斑变换器的第一光波导10耦合到第二光波导20并传输到氮化硅光波导50内,经氮化硅光波导50耦合到顶层硅上的光有源器件60内。As shown in FIG. 8, this embodiment provides a silicon optical integrated chip, which includes a substrate 31, a lower cladding layer 32, a top layer of silicon, a silicon nitride layer, and an upper cladding layer 34. Among them, an optical active device 60, such as a photodetector, is provided on the top silicon, and a silicon nitride optical waveguide 50 is provided on the silicon nitride layer. The figure shows only a part of the silicon optical integrated chip, which simply shows a cross-sectional schematic diagram of a silicon nitride optical waveguide 50. The silicon nitride layer on the silicon optical integrated chip can be designed with several silicon nitride optical waveguides according to actual needs. Optical passive components such as wavelength division multiplexer or coupler. The mode spot converter of any one of the above-mentioned embodiments 1-3 is provided near the end face where the silicon optical integrated chip is coupled with the external optical fiber 70. The thickness of the second optical waveguide 20 of the mode spot converter and the silicon nitride layer The thickness is the same, and is connected to the silicon nitride optical waveguide 50 of the silicon optical integrated chip. The top layer of silicon near the external optical fiber is thinned into a thin silicon waveguide (first optical waveguide 10), which has a better matching degree with the optical field of the external optical fiber 70. The optical signal output by the external optical fiber 70 is coupled to the second optical waveguide 20 through the first optical waveguide 10 of the mode spot converter and transmitted into the silicon nitride optical waveguide 50, and is coupled to the light on the top silicon via the silicon nitride optical waveguide 50. Active device 60 within.
当然,因为光路的可逆性,在其它实施例中,光有源器件60也可以是光调制器,输出调制的光信号经氮化硅光波导50传输到模斑变换器的第二光波导20,经第二光波导20耦合到第一光波导10之后,从第一光波导10耦合到外部光纤70内,由外部光纤70输出光信号。Of course, because of the reversibility of the optical path, in other embodiments, the optical active device 60 may also be an optical modulator, and the output modulated optical signal is transmitted to the second optical waveguide 20 of the mode spot converter through the silicon nitride optical waveguide 50. After being coupled to the first optical waveguide 10 via the second optical waveguide 20, the first optical waveguide 10 is coupled to the external optical fiber 70, and the external optical fiber 70 outputs an optical signal.
该实施例中的硅光集成芯片采用氮化硅作为光波导进行光传输,具有更好的热稳定性和更低的传输损耗,而且采用上述任一实施例中的模斑变换器与外部光纤进行耦合,与光纤具有更高的模式匹配度和耦合效率,同时具有更低的偏振相关损耗。The silicon optical integrated chip in this embodiment uses silicon nitride as an optical waveguide for optical transmission, which has better thermal stability and lower transmission loss, and uses the mode spot converter and external optical fiber in any of the above embodiments. For coupling, it has a higher mode matching degree and coupling efficiency with the optical fiber, and at the same time has a lower polarization-related loss.
上文所列出的一系列的详细说明仅仅是针对本申请的可行性实施方式的具体说明,它们并非用以限制本申请的保护范围,凡未脱离本申请技艺精神所作的等效实施方式或变更均应包含在本申请的保护范围之内。The series of detailed descriptions listed above are only specific descriptions of the feasible implementation manners of this application. They are not used to limit the scope of protection of this application. All changes shall be included in the scope of protection of this application.
Claims (14)
- 一种模斑变换器,具有与外部光纤光耦合的第一端面和与外部光器件光耦合的第二端面,其特征在于,所述模斑变换器包括:A mode spot converter has a first end face optically coupled with an external optical fiber and a second end face optically coupled with an external optical device, characterized in that the mode spot converter includes:第一光波导,包括第一楔形结构和第二楔形结构,所述第一楔形结构的尖端临近所述第一端面,所述第二楔形结构的尖端朝向与所述第一楔形结构的尖端相背的方向;The first optical waveguide includes a first wedge structure and a second wedge structure, the tip of the first wedge structure is adjacent to the first end surface, and the tip of the second wedge structure faces the same as the tip of the first wedge structure Back direction第二光波导,包括第三楔形结构,所述第三楔形结构与所述第二楔形结构至少部分重叠以将所述第二楔形结构中的光模式绝热地耦合到所述第三楔形结构中;所述第三楔形结构的尖端朝向所述第一楔形结构。The second optical waveguide includes a third wedge-shaped structure that at least partially overlaps the second wedge-shaped structure to adiabatically couple the optical mode in the second wedge-shaped structure into the third wedge-shaped structure ; The tip of the third wedge-shaped structure faces the first wedge-shaped structure.
- 根据权利要求1所述的模斑变换器,其特征在于:所述模斑变换器还包括衬底和设于所述衬底上的下包层,所述第一光波导和第二光波导设于所述下包层上。The mode spot converter according to claim 1, wherein the mode spot converter further comprises a substrate and a lower cladding layer provided on the substrate, the first optical waveguide and the second optical waveguide Set on the lower cladding layer.
- 根据权利要求2所述的模斑变换器,其特征在于:所述第一光波导和第二光波导之间还设有中间包层,所述中间包层的折射率小于所述第一光波导和第二光波导的折射率。The mode spot converter according to claim 2, wherein an intermediate cladding layer is further provided between the first optical waveguide and the second optical waveguide, and the refractive index of the intermediate cladding layer is smaller than that of the first optical waveguide. The refractive index of the waveguide and the second optical waveguide.
- 根据权利要求3所述的模斑变换器,其特征在于:所述中间包层的厚度小于或等于3微米。The mode spot converter according to claim 3, wherein the thickness of the intermediate cladding layer is less than or equal to 3 microns.
- 根据权利要求2所述的模斑变换器,其特征在于:所述第一端面在所述第一光波导下方临近所述下包层的衬底处设有挖空部。3. The mode spot converter according to claim 2, wherein the first end surface is provided with a hollow portion below the first optical waveguide and adjacent to the substrate of the under-cladding layer.
- 根据权利要求2所述的模斑变换器,其特征在于:所述第一光波导为硅波导,所述第二光波导为氮化硅波导,所述硅波导位于所述下包层上方,所述氮化硅波导位于所述硅波导上方。The mode spot converter according to claim 2, wherein the first optical waveguide is a silicon waveguide, the second optical waveguide is a silicon nitride waveguide, and the silicon waveguide is located above the lower cladding layer, The silicon nitride waveguide is located above the silicon waveguide.
- 根据权利要求1所述的模斑变换器,其特征在于:所述第一光波导的厚度小于或等于所述第二光波导的厚度。The mode spot converter according to claim 1, wherein the thickness of the first optical waveguide is less than or equal to the thickness of the second optical waveguide.
- 根据权利要求7所述的模斑变换器,其特征在于:所述第一光波导的厚度在60~200nm范围内,所述第二光波导的厚度在200~800nm的范围内。7. The mode spot converter according to claim 7, wherein the thickness of the first optical waveguide is in the range of 60-200 nm, and the thickness of the second optical waveguide is in the range of 200-800 nm.
- 根据权利要求7所述的模斑变换器,其特征在于:所述第一楔形结构的尖端横截面的宽度小于或等于200nm;所述第三楔形结构的尖端横截面的宽度在100nm~300nm范围内。7. The mode spot converter according to claim 7, wherein: the width of the tip cross section of the first wedge structure is less than or equal to 200 nm; the width of the tip cross section of the third wedge structure is in the range of 100 nm to 300 nm Inside.
- 根据权利要求1-9任一项所述的模斑变换器,其特征在于:所述第二光波导还包括边耦合结构,所述边耦合结构一端与所述第三楔形结构的尖端连接,另一端偏离所述第二光波导的中心轴线向所述第一光波导的边缘延伸以将所述第一光波导中的光模式绝热地耦合到所述第二光波导中。The mode spot converter according to any one of claims 1-9, wherein the second optical waveguide further comprises an edge coupling structure, one end of the edge coupling structure is connected to the tip of the third wedge structure, The other end deviates from the central axis of the second optical waveguide and extends toward the edge of the first optical waveguide to adiabatically couple the optical mode in the first optical waveguide into the second optical waveguide.
- 根据权利要求10所述的模斑变换器,其特征在于:所述边耦合结构远离所述第三楔形结构的一端的横截面宽度小于或等于200nm。10. The mode spot converter according to claim 10, wherein the cross-sectional width of an end of the side coupling structure away from the third wedge structure is less than or equal to 200 nm.
- 根据权利要求10所述的模斑变换器,其特征在于:所述边耦合结构远离所述第三楔形结构的一端延伸出所述第一光波导边缘。10. The mode spot converter according to claim 10, wherein an end of the edge coupling structure away from the third wedge structure extends out of the edge of the first optical waveguide.
- 根据权利要求1-9任一项所述的模斑变换器,其特征在于:所述第二光波导还包括线性结构,所述线性结构设于所述第三楔形结构与所述第二端面之间。The mode spot converter according to any one of claims 1-9, wherein the second optical waveguide further comprises a linear structure, and the linear structure is provided on the third wedge-shaped structure and the second end surface. between.
- 一种硅光集成芯片,其特征在于:A silicon-optical integrated chip, which is characterized in:所述硅光集成芯片包括衬底、下包层、顶层硅、氮化硅层和上包层;The silicon-optical integrated chip includes a substrate, a lower cladding layer, a top layer of silicon, a silicon nitride layer, and an upper cladding layer;所述顶层硅上设有光有源器件,所述氮化硅层设有氮化硅光波导;Optical active devices are provided on the top layer of silicon, and silicon nitride optical waveguides are provided on the silicon nitride layer;所述硅光集成芯片上临近所述硅光集成芯片与外部光纤的耦合端面设有如权利要求1-13任一项所述的模斑变换器;The silicon optical integrated chip is provided with the mode spot converter according to any one of claims 1-13 adjacent to the coupling end surface of the silicon optical integrated chip and the external optical fiber;所述外部光纤输出的光信号经所述模斑变换器的第一光波导耦合到所述第二光波导并传输到所述氮化硅光波导内,经所述氮化硅光波导耦合到所述顶层硅上的光有源器件内。The optical signal output by the external optical fiber is coupled to the second optical waveguide via the first optical waveguide of the mode spot converter and transmitted into the silicon nitride optical waveguide, and is coupled to the silicon nitride optical waveguide via the silicon nitride optical waveguide. Inside the photoactive device on the top layer of silicon.
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