WO2021175072A1 - 一种半导体光耦合结构和硅光集成芯片 - Google Patents

一种半导体光耦合结构和硅光集成芯片 Download PDF

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Publication number
WO2021175072A1
WO2021175072A1 PCT/CN2021/075148 CN2021075148W WO2021175072A1 WO 2021175072 A1 WO2021175072 A1 WO 2021175072A1 CN 2021075148 W CN2021075148 W CN 2021075148W WO 2021175072 A1 WO2021175072 A1 WO 2021175072A1
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optical
waveguide
wedge
silicon
coupling structure
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PCT/CN2021/075148
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English (en)
French (fr)
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季梦溪
李显尧
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苏州旭创科技有限公司
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Publication of WO2021175072A1 publication Critical patent/WO2021175072A1/zh

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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
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements

Definitions

  • This application relates to the field of optical communication technology, and in particular to a semiconductor optical coupling structure 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 grating coupler 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 of the fiber and the coupler, but the coupling efficiency is selective to the wavelength and the polarization state.
  • the specially designed two-dimensional grating can reduce the selectivity to the polarization state, but it is still sensitive to the wavelength. Will reduce the coupling efficiency. Based on the horizontal coupling of the mode spot converter, the coupling efficiency is high and the selectivity to wavelength and polarization state is relatively small.
  • the current mode spot converter generally couples with an external optical fiber through a section of graded silicon waveguide to gradually evolve the optical mode into the silicon waveguide.
  • the characteristic of this structure is that the smaller the tip size of the graded silicon waveguide, the greater the coupling efficiency. Therefore, in order to obtain higher coupling efficiency, the general tip width needs to be less than 100nm, which basically reaches the limit of the current processing level of most silicon photonics factories.
  • the thickness of the tip is determined by the thickness of the top silicon of the SOI (silicon on insulator) wafer (generally 200-300nm), and it is generally difficult to make it small. Therefore, the actual finished product of this tip is approximately a rectangle whose height is one to two times larger than its width.
  • the polarization selectivity of the above structure is very large, that is, the coupling efficiency to the TE mode is high, the coupling efficiency to the TM mode is low, and the polarization-dependent loss is large, which is not suitable for the optical receiving end.
  • the purpose of this application is to provide a semiconductor optical coupling structure and a silicon optical integrated chip, which can effectively reduce optical polarization-related losses and improve coupling efficiency.
  • the present application provides a semiconductor optical coupling structure having a first end surface optically coupled with an external optical fiber and a second end surface optically coupled with an external optical device;
  • the optical coupling structure includes:
  • the first optical waveguide includes a cantilever waveguide with a first refractive index, and the cantilever waveguide is adjacent to the first end surface;
  • the second optical waveguide includes a first wedge-shaped structure, a first linear structure, and a second wedge-shaped structure connected in sequence, and the thickness of the second wedge-shaped structure is greater than the thickness of the first wedge-shaped structure and the first linear structure;
  • the two optical waveguides have a second refractive index, and the first refractive index is lower than the second refractive index;
  • the cantilever waveguide at least partially covers the tip of the first wedge-shaped structure, one end of the first linear structure is connected to the wider end of the first wedge-shaped structure, and the other end of the first linear structure at least partially surrounds Both sides of the tip of the second wedge-shaped structure.
  • the thickness of the first wedge structure and the first linear structure is less than or equal to 300 nm, and the thickness of the second wedge structure is less than or equal to 400 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 second wedge structure is less than or equal to 200 nm.
  • the first linear structure covers both sides of the second wedge structure; the lengths of the first wedge structure and the second wedge structure are both greater than or equal to 10 ⁇ m.
  • the first refractive index ranges from 1.35 to 1.5
  • the second refractive index ranges from 3.4 to 3.6.
  • the optical coupling structure further includes a substrate and a cladding layer provided on the substrate; the first optical waveguide is adjacent to the first end surface and suspended above the substrate The second optical waveguide is a silicon waveguide provided in the cladding.
  • the width of the waveguide cross section of the cantilever waveguide is in the range of 2-15 ⁇ m, and the height is in the range of 2-15 ⁇ m.
  • the width of the cantilever of the cantilever waveguide along the light propagation direction is greater than or equal to 1 ⁇ m
  • the length of the cantilever is less than or equal to 15 ⁇ m
  • the interval between adjacent cantilevers is greater than or equal to 5 ⁇ m.
  • the second optical waveguide further includes a second linear structure, and the second linear structure is provided between the second wedge-shaped structure and the second end surface.
  • the second linear structure is a multimode optical waveguide.
  • the present application also provides a silicon optical integrated chip provided with the optical coupling structure according to any one of the above embodiments; the optical coupling structure is adjacent to the end surface of the silicon optical integrated chip, and the silicon optical integrated chip passes The optical coupling structure is optically coupled with an external optical waveguide.
  • the silicon optical integrated chip is also provided with an optical detector, and the optical signal output by the external optical waveguide is coupled to the second optical waveguide via the first optical waveguide of the optical coupling structure, and The second optical waveguide is coupled into the optical detector.
  • a multimode optical waveguide is further provided between the optical coupling structure and the optical detector, and the multimode optical waveguide connects the optical coupling structure and the optical detector.
  • the silicon optical integrated chip is also provided with one or a combination of an optical modulator, an optical demodulator, a wavelength division multiplexer, and a wavelength division multiplexer.
  • FIG. 1 is a schematic diagram of a semiconductor light coupling structure and a cross-sectional view of the application
  • FIG. 2 is a schematic diagram of a part of the structure of the silicon-optical integrated chip of this 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.
  • the semiconductor optical coupling structure of the present application is formed on the edge of the SOI (silicon on insulator) chip, and is used for the optical coupling of the edge of the silicon optical integrated chip, especially for the optical coupling between the light receiving end and the external optical fiber. coupling.
  • SOI silicon on insulator
  • the semiconductor optical coupling structure has 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, where the first end face A and the second end face B are arranged oppositely.
  • the optical coupling structure includes a first optical waveguide 11 and a second optical waveguide 20, wherein the first optical waveguide 11 includes a cantilever waveguide having a first refractive index, and the cantilever waveguide is adjacent to the first end face A.
  • the proximity of the cantilever waveguide to the first end face A means that the cantilever waveguide is closer to the first end face A than other waveguides such as the second optical waveguide.
  • “near" all means closer and closer. Go into details.
  • the second optical waveguide 20 includes a first wedge structure 21, a first linear structure 22 and a second wedge structure 23 connected in sequence.
  • the second optical waveguide has a second refractive index, and the first refractive index is lower than the second refractive index.
  • the first refractive index ranges from 1.35 to 1.5
  • the second refractive index ranges from 3.4 to 3.6.
  • the thickness of the aforementioned second wedge structure 23 is greater than the thickness of the first wedge structure 21 and the first linear structure 22.
  • the above-mentioned cantilever waveguide at least partially covers the tip of the first wedge structure 21 to couple the light in the cantilever waveguide into the first wedge structure 21; one end of the first linear structure 22 is connected to the wider end of the first wedge structure 21 The other end of the first linear structure 22 at least partially surrounds both sides of the tip of the second wedge-shaped structure 23 to couple the light in the first linear structure 22 to the second wedge-shaped structure 23.
  • the above-mentioned optical coupling structure is a semiconductor structure having a substrate 30 and a cladding layer 10 provided on the substrate 30, and the above-mentioned first optical waveguide 11 is a cladding waveguide (ie, The above-mentioned cantilever waveguide), the second optical waveguide 20 is a silicon waveguide provided in the cladding 10.
  • the cantilever waveguide of the first optical waveguide 11 is formed by etching a part of the cladding layer adjacent to the first end face A, and there is a hollow structure 31 between the first optical waveguide 11 and the substrate 30 (refer to the cross section at C).
  • the substrate 30 is a silicon substrate
  • the cladding layer 10 is a silicon dioxide cladding layer.
  • the width D1 of the waveguide cross-section of the cantilever waveguide is in the range of 2 ⁇ 15 ⁇ m, and the height H1 is in the range of 2 ⁇ 15 ⁇ m, which can have higher mode matching with the external optical fiber, and is better with the second optical waveguide. ⁇ coupled.
  • the width L1 of the cantilever 12 of the cantilever waveguide along the light propagation direction is greater than or equal to 1 ⁇ m, the length D4 of the cantilever 12 is less than or equal to 15 ⁇ m, and the interval L2 between adjacent cantilevers is greater than or equal to 5 ⁇ m, so that the cantilever waveguide has lower optical transmission loss, At the same time, it has good mechanical strength.
  • the first wedge-shaped structure 21 of the second optical waveguide 20 is a section of a graded waveguide made of thin silicon (refer to the cross section at D) provided at the other end of the cantilever waveguide 11. In this area, light gradually evolves from the silicon dioxide cantilever waveguide 11 to the thin silicon graded waveguide (first wedge structure 21).
  • the light in the thin silicon is coupled to the thick silicon (refer to the cross section at E) through the coupling of the first linear structure 22 formed by a section of thin silicon and the graded waveguide formed by thick silicon (the second wedge structure 23), and then pass
  • the thick silicon is coupled with external optical devices.
  • the external optical device may be a photodetector integrated on a silicon optical chip or the like.
  • the thickness H2 of the first wedge-shaped structure 21 and the first linear structure 22, that is, the thickness of thin silicon is less than or equal to 300 nm, preferably less than or equal to 220 nm, and the thickness H3 of the second wedge-shaped structure 23 is thick
  • the thickness of the silicon is consistent with the thickness of the top silicon of the SOI, and is less than or equal to 400 nm.
  • the width D2 of the tip cross section of the first wedge structure 21 is less than or equal to 200 nm
  • the width D3 of the tip cross section of the second wedge structure 23 is less than or equal to 200 nm.
  • the first linear structure 22 covers both sides of the second wedge structure 23, wherein the lengths of the first wedge structure 21 and the second wedge structure 23 are both greater than or equal to 10 ⁇ m.
  • the structure is coupled with an external optical fiber through a silica cantilever waveguide whose refractive index is similar to that of the optical fiber, which can reduce the loss caused by the sudden change of the refractive index and effectively improve the coupling efficiency.
  • a gradual structure from thin silicon to thick silicon is adopted.
  • the tip of the thin silicon waveguide can be made small in both the horizontal and vertical dimensions, which improves the first optical waveguide.
  • the optical mode matching with the second optical waveguide can effectively reduce the polarization-related loss and further improve the coupling efficiency.
  • the second optical waveguide 20 further includes a second linear structure 24 disposed between the second wedge-shaped structure 23 and the second end surface B. That is, behind the second wedge-shaped structure 23 of the second optical waveguide 20 there is a relatively wide (supporting high-order mode) thick silicon waveguide (refer to the cross section at F), that is, the second linear structure 24. After the light enters the thick silicon, it couples with an external optical device through the second linear structure 24.
  • the second linear structure 24 is a multi-mode optical waveguide and supports high-order modes, so that all modes can enter the external optical device with a small loss, which further improves the coupling efficiency. As shown in FIG. 2, it is a silicon optical integrated chip integrated with the above-mentioned optical coupling structure.
  • the optical coupling structure is adjacent to the end face of the silicon optical integrated chip, and the silicon optical integrated chip is optically coupled to an external optical waveguide through the optical coupling structure.
  • the silicon optical integrated chip is also provided with a photodetector 40, and the optical signal output by the external optical waveguide 50 is coupled to the second optical waveguide 20 via the first optical waveguide 11 of the above-mentioned optical coupling structure, and then via the second optical waveguide.
  • the waveguide 20 is coupled into the photodetector 40.
  • the external optical waveguide 50 uses a single-mode optical fiber, and other optical fibers or optical waveguides may also be used in other embodiments. That is, the above-mentioned optical coupling structure is arranged on the edge of the silicon optical integrated chip for optical coupling between the external optical fiber and the photodetector 40.
  • optical coupling structure with high coupling efficiency is designed on the edge of the silicon optical integrated chip, which reduces the coupling loss of light from the external optical fiber to the photodetector, and effectively improves the responsivity of the photodetector.
  • a multi-mode optical waveguide may also be provided between the optical coupling structure and the optical detector, and the multi-mode optical waveguide connects the optical coupling structure and the optical detector.
  • the multimode optical waveguide supports high-order modes, so that all modes can enter the photodetector with a small loss, which can further improve the responsivity.
  • Figure 2 only shows a part of the silicon optical integrated chip.
  • the silicon optical integrated chip can also be equipped with other active or passive optical devices such as optical modulator and/or wavelength division multiplexing/demultiplexing.
  • other active or passive optical devices such as optical modulator and/or wavelength division multiplexing/demultiplexing.
  • a wavelength division multiplexer and/or an optical demodulator may also be provided between the optical coupling structure and the optical detector.
  • the optical coupler can also be provided on the end surface of the light emitting end or other silicon optical integrated chips to realize the connection between the silicon optical integrated chip and the external optical waveguide.
  • Edge coupling For example, it is used for the edge coupling of the output optical signal of the optical modulator and/or the wavelength division multiplexer in the silicon optical integrated chip with the external optical waveguide.

Abstract

一种半导体光耦合结构和硅光集成芯片。半导体光耦合结构具有与外部光纤（50）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）。光耦合结构包括相耦合连接的第一光波导（11）和第二光波导（20），其中，第一光波导（11）包括具有第一折射率的悬臂波导，悬臂波导临近第一端面（A）；第二光波导（20）具有第二折射率，包括依次连接的第一楔形结构（21）、第一线性结构（22）和第二楔形结构（23），第二楔形结构（23）的厚度大于第一楔形结构（21）和第一线性结构（22）的厚度。第一折射率低于第二折射率。耦合结构结合了悬臂波导和多层渐变波导的优势，有效降低耦合光损耗，提高了光耦合效率和光接收端的响应度。

Description

一种半导体光耦合结构和硅光集成芯片 技术领域
本申请涉及光通信技术领域，尤其涉及一种半导体光耦合结构和硅光集成芯片。
 背景技术
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，但耦合效率对波长和偏振态具有选择性，经过特殊设计的二维光栅能够降低对偏振态的选择性，但依然对波长敏感，并且会降低耦合效率。基于模斑转换器的水平耦合，耦合效率高并且对波长和偏振态的选择性相对较小。
目前的模斑转换器一般是通过一段渐变硅波导与外部光纤耦合，将光模式逐渐演化到硅波导中。这种结构的特点在于渐变硅波导的尖端尺寸越小，耦合效率越大。所以要得到较高的耦合效率，一般尖端宽度需要做到小于100nm，这基本达到了目前大部分硅光代工厂的加工水平的极限。而尖端的厚度由SOI（silicon on insulator，绝缘体上硅）晶圆的顶层硅厚度（一般在200-300nm）决定，一般很难做小。因此这种尖端的实际成品大约是一个高度比宽度大一到两倍的长方形。
 技术问题
上述结构的偏振选择性很大，即对TE模式的耦合效率较高，对TM模式的耦合效率较低，偏振相关损耗较大，不适用在光接收端。
 技术解决方案
本申请的目的在于提供一种半导体光耦合结构和硅光集成芯片，可有效降低光偏振相关损耗，提高耦合效率。
为了实现上述目的之一，本申请提供了一种半导体光耦合结构，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；所述光耦合结构包括：
第一光波导，包括具有第一折射率的悬臂波导，所述悬臂波导临近所述第一端面；
第二光波导，包括依次连接的第一楔形结构、第一线性结构和第二楔形结构，所述第二楔形结构的厚度大于所述第一楔形结构和第一线性结构的厚度； 所述第二光波导具有第二折射率，所述第一折射率低于所述第二折射率；
所述悬臂波导至少部分包覆所述第一楔形结构的尖端，所述第一线性结构的一端与所述第一楔形结构较宽的一端连接，所述第一线性结构的另一端至少部分围绕所述第二楔形结构的尖端的两侧。
作为实施方式的进一步改进，所述第一楔形结构和第一线性结构的厚度小于或等于300nm，所述第二楔形结构的厚度小于或等于400nm。
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；所述第二楔形结构的尖端横截面的宽度小于或等于200nm。
作为实施方式的进一步改进，所述第一线性结构包覆所述第二楔形结构的两侧；所述第一楔形结构和第二楔形结构的长度均大于或等于10μm。
作为实施方式的进一步改进，所述第一折射率的范围在1.35~1.5，所述第二折射率的范围在3.4~3.6。
作为实施方式的进一步改进，所述光耦合结构还包括衬底、设于所述衬底上的包层；所述第一光波导为临近所述第一端面且悬浮于所述衬底之上的包层波导，所述第二光波导为设于所述包层内的硅波导。
作为实施方式的进一步改进，所述悬臂波导的波导横截面的宽度在2~15μm的范围内，高度在2~15μm的范围内。
作为实施方式的进一步改进，所述悬臂波导的悬臂沿光传播方向的宽度大于或等于1μm，悬臂长度小于或等于15μm，相邻悬臂之间的间隔大于或等于5μm。
作为实施方式的进一步改进，所述第二光波导还包括第二线性结构，所述第二线性结构设于所述第二楔形结构与所述第二端面之间。
作为实施方式的进一步改进，所述第二线性结构为多模光波导。
本申请还提供了一种硅光集成芯片，设有上述任一项实施方式所述的光耦合结构；所述光耦合结构临近所述硅光集成芯片的端面处，所述硅光集成芯片通过所述光耦合结构与外部光波导光耦合。
作为实施方式的进一步改进，所述硅光集成芯片内还设有光探测器，外部光波导输出的光信号经所述光耦合结构的第一光波导耦合到所述第二光波导，经所述第二光波导耦合到所述光探测器内。
作为实施方式的进一步改进，所述光耦合结构与所述光探测器之间还设有多模光波导，所述多模光波导连接所述光耦合结构和所述光探测器。
作为实施方式的进一步改进，所述硅光集成芯片内还设有光调制器、光解调器、波分复用器和波分解复用器其中的一种或多种的组合。
 有益效果
结合了悬臂波导和多层渐变波导的优势，有效降低耦合光损耗，提高了光耦合效率和光接收端的响应度。
 附图说明
图1为本申请半导体光耦合结构及截面示意图；
图2为本申请硅光集成芯片部分结构示意图。
 本发明的实施方式
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。
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。
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。
本申请的半导体光耦合结构是形成于SOI（silicon on insulator，绝缘体上硅）的芯片边缘，用于硅光集成芯片边缘光耦合的结构，特别是用于光接收端与外部光纤之间的光耦合。
如图1所示，该半导体光耦合结构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，这里第一端面A和第二端面B相对设置。该光耦合结构包括第一光波导11和第二光波导20，其中，第一光波导11包括具有第一折射率的悬臂波导，该悬臂波导临近第一端面A。这里，悬臂波导临近第一端面A指的是悬臂波导与第二光波导等其它波导相比更靠近第一端面A，下文中的“临近”均同指更靠近、更接近的意思，不再赘述。第二光波导20包括依次连接的第一楔形结构21、第一线性结构22和第二楔形结构23。该第二光波导具有第二折射率，上述第一折射率低于该第二折射率，该实施例中，第一折射率的范围在1.35~1.5，第二折射率的范围在3.4~3.6。上述第二楔形结构23的厚度大于第一楔形结构21和第一线性结构22的厚度。上述悬臂波导至少部分包覆该第一楔形结构21的尖端，以将悬臂波导中的光耦合到第一楔形结构21中；第一线性结构22的一端与第一楔形结构21较宽的一端连接，第一线性结构22的另一端至少部分围绕第二楔形结构23的尖端的两侧，以将第一线性结构22中的光耦合到第二楔形结构23中。
上述光耦合结构为具有衬底30和设于衬底30上的包层10的半导体结构，上述第一光波导11为临近第一端面A且悬浮于衬底30之上的包层波导（即上述悬臂波导），第二光波导20为设于包层10内的硅波导。其中，第一光波导11的悬臂波导为由临近第一端面A的部分包层刻蚀形成，第一光波导11与衬底30之间具有挖空结构31（参考C处的截面）。这里，衬底30为硅衬底，包层10为二氧化硅包层。该实施例中，悬臂波导的波导横截面的宽度D1在2~15μm的范围内，高度H1在2~15μm的范围内，可以跟外部光纤具有较高的模式匹配，跟第二光波导更好地耦合。悬臂波导的悬臂12沿光传播方向的宽度L1大于或等于1μm，悬臂12长度D4小于或等于15μm，相邻悬臂之间的间隔L2大于或等于5μm，使得悬臂波导具有更低的光传输损耗，同时具有较好的机械强度。光从外部单模光纤入射，先进入第一光波导11，由于第一光波导11（二氧化硅）中光的有效折射率和单模光纤的有效折射率近似相等，而且悬臂波导11与衬底30之间具有挖空结构，可减少光模式从衬底30损耗掉，因此具有很高的耦合效率。第二光波导20的第一楔形结构21为设在悬臂波导11另一端的一段由薄硅形成的渐变波导（参考D处的截面）。在这个区域内，光逐渐由二氧化硅的悬臂波导11中演化到薄硅的渐变波导（第一楔形结构21）中。然后通过一段薄硅形成的第一线性结构22与厚硅形成的渐变波导（第二楔形结构23）的耦合，将薄硅中的光耦合到厚硅中（参考E处的截面），再通过厚硅与外部光器件耦合。这里，外部光器件可以是集成在硅光芯片上的光探测器等。
该实施例中，第一楔形结构21和第一线性结构22的厚度H2，即薄硅的厚度，小于或等于300nm，以小于或等于220nm为优，第二楔形结构23的厚度H3，即厚硅的厚度，与SOI的顶层硅厚度一致，小于或等于400nm。为了具有更好的模式匹配，第一楔形结构21的尖端横截面的宽度D2小于或等于200nm，第二楔形结构23的尖端横截面的宽度D3小于或等于200nm。第一线性结构22包覆第二楔形结构23的两侧，其中，第一楔形结构21和第二楔形结构23的长度均大于或等于10μm。该结构通过折射率与光纤折射率近似的二氧化硅悬臂波导与外部光纤耦合，可减少因折射率突变引起的损耗，有效提高了耦合效率。另外，采用了薄硅到厚硅的渐变结构，可以在二氧化硅到顶层硅的耦合结构中，将薄硅波导的尖端在横向和纵向的尺寸都做到很小，提高了第一光波导和第二光波导的光模式匹配，可有效降低偏振相关损耗，进一步提高了耦合效率。
该实施例中，第二光波导20还包括第二线性结构24，该第二线性结构24设于第二楔形结构23与第二端面B之间。即，在第二光波导20的第二楔形结构23后面还有一段比较宽（支持高阶模式）的厚硅波导（参考F处的截面），即第二线性结构24。光进入厚硅之后，通过该第二线性结构24与外部光器件耦合。该第二线性结构24为多模光波导，支持高阶模式，使得所有模式都能以较小的损耗进入到外部光器件内，进一步提高了耦合效率。如图2所示，为集成了上述光耦合结构的硅光集成芯片，该光耦合结构临近硅光集成芯片的端面处，硅光集成芯片通过该光耦合结构与外部光波导光耦合。
该实施例中，硅光集成芯片内还设有光探测器40，外部光波导50输出的光信号经上述光耦合结构的第一光波导11耦合到第二光波导20，再经第二光波导20耦合到光探测器40内。这里，外部光波导50采用的是单模光纤，在其它实施例中也可以采用其它光纤或光波导。即上述光耦合结构设在硅光集成芯片的边缘，用于外部光纤与光探测器40之间的光耦合。在硅光集成芯片的边缘设计了上述具有高耦合效率的光耦合结构，降低了光从外部光纤到光探测器之间的耦合损耗，有效提高了光探测器的响应度。
在光耦合结构与光探测器之间还可以设有多模光波导，该多模光波导连接光耦合结构和光探测器。多模光波导支持高阶模式，使得所有模式都能以较小的损耗进入到光探测器内，可进一步提高响应度。
图2仅示出了硅光集成芯片的一部分，实际设计中，硅光集成芯片内还可以设有光调制器和/或波分复用/解复用器等其它有源或无源光器件。例如，在光耦合结构与光探测器之间还可以设有波分解复用器和/或光解调器等。
上述实施例仅以光接收端的光路为例进行阐述，在其它实施例中，也可在光发射端或其它硅光集成芯片的端面设置上述光耦合器，实现硅光集成芯片与外部光波导的边缘耦合。例如，用于硅光集成芯片内光调制器和/或波分复用器输出光信号与外部光波导的边缘耦合。
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。 

Claims (14)

  1. 一种半导体光耦合结构，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：所述光耦合结构包括：
    第一光波导，包括具有第一折射率的悬臂波导，所述悬臂波导临近所述第一端面；
    第二光波导，包括依次连接的第一楔形结构、第一线性结构和第二楔形结构，所述第二楔形结构的厚度大于所述第一楔形结构和第一线性结构的厚度； 所述第二光波导具有第二折射率，所述第一折射率低于所述第二折射率；
    所述悬臂波导至少部分包覆所述第一楔形结构的尖端，所述第一线性结构的一端与所述第一楔形结构较宽的一端连接，所述第一线性结构的另一端至少部分围绕所述第二楔形结构的尖端的两侧。
  2. 根据权利要求1的光耦合结构，其特征在于：所述第一楔形结构和第一线性结构的厚度小于或等于300nm，所述第二楔形结构的厚度小于或等于400nm。
  3. 根据权利要求2所述的光耦合结构，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；所述第二楔形结构的尖端横截面的宽度小于或等于200nm。
  4. 根据权利要求1所述的光耦合结构，其特征在于：所述第一线性结构包覆所述第二楔形结构的两侧；所述第一楔形结构和第二楔形结构的长度均大于或等于10μm。
  5. 根据权利要求1所述的光耦合结构，其特征在于：所述第一折射率的范围在1.35~1.5，所述第二折射率的范围在3.4~3.6。
  6. 根据权利要求1所述的光耦合结构，其特征在于：所述光耦合结构还包括衬底、设于所述衬底上的包层；所述第一光波导为临近所述第一端面且悬浮于所述衬底之上的包层波导，所述第二光波导为设于所述包层内的硅波导。
  7. 根据权利要求6所述的光耦合结构，其特征在于：所述悬臂波导的波导横截面的宽度在2~15μm的范围内，高度在2~15μm的范围内。
  8. 根据权利要求6所述的光耦合结构，其特征在于：所述悬臂波导的悬臂沿光传播方向的宽度大于或等于1μm，悬臂长度小于或等于15μm，相邻悬臂之间的间隔大于或等于5μm。
  9. 根据权利要求1-8任一项所述的光耦合结构，其特征在于：所述第二光波导还包括第二线性结构，所述第二线性结构设于所述第二楔形结构与所述第二端面之间。
  10. 根据权利要求9所述的光耦合结构，其特征在于：所述第二线性结构为多模光波导。
  11. 一种硅光集成芯片，其特征在于：设有权利要求1-10任一项所述的光耦合结构；所述光耦合结构临近所述硅光集成芯片的端面处，所述硅光集成芯片通过所述光耦合结构与外部光波导光耦合。
  12. 根据权利要求11所述的硅光集成芯片，其特征在于：所述硅光集成芯片内还设有光探测器，外部光波导输出的光信号经所述光耦合结构的第一光波导耦合到所述第二光波导，经所述第二光波导耦合到所述光探测器内。
  13. 根据权利要求12所述的硅光集成芯片，其特征在于：所述光耦合结构与所述光探测器之间还设有多模光波导，所述多模光波导连接所述光耦合结构和所述光探测器。
  14. 根据权利要求11-13任一项所述的硅光集成芯片，其特征在于：所述硅光集成芯片内还设有光调制器、光解调器、波分复用器和波分解复用器其中的一种或多种的组合。
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