InP基高度集成沟槽型马赫-曾德电光开关及其阵列的研究

High speed optical switches and its matrix are critical components in the realization of light transmission path switching technology for optical networks.Compact optical waveguide-based switches are promising technique in the application of dense photonic integrated circuits (PIC) on a chip scale. However, current optical switches are still limited due to the large footprint of the devices. To date it is a hot topic to drive the real estate of these devices to a micro/nano-scale level,improve integration, and reduce the power consumption as well. This project aims to develop an ultra-compact InP-based Mach-Zehnder Interferometer (MZI) type electro-optical switch unit and its 4x4 switch matrix for the purpose of large-scale PIC. The novel MZI-based switch consists of nanophotonic frustrated total internal reflection couplers and total internal reflection mirror-based 90 degree waveguide bends. The couplers and the bends are realized by etching of a deep trench in the intersection of "+" and "L" waveguide structure, respectively. There are significant technical and economic advantages to the novel InP MZI electro-optical switch. The configuration of the device may significantly reduce the chip size and easily scale its pattern in the two-dimensional direction. Also, the configuration may be beneficial to the demonstration of a 4x4 integrated switch matrix because of a potential low power-consumption and a fast response time of the chip. The mechanism of frustrated total internal reflection phenomenon is investigated through the study of interaction of guided-wave beams transiting a thin trench from the waveguides. The total device structure is optimized by the simulation of Goos-Hanchen shift using 3D Finite-difference time-domain method.In addition, the project is useful to improve micro-fabrication technology of InP-based submicron/nanoscale opening trench with a high aspect ratio. The investigation of the project provides a new idea and a new method for two-dimensional dense planar integration of InP-based photonic integrated circuits.

高速光开关及其阵列是实现光传输路径变换的关键器件之一。目前波导型光开关一维尺度较长或者占据面积相对较大而限制其在光子集成回路中的应用，因此降低器件尺寸和能耗并提高集成度是国内外研究的热门课题。本项目旨在开展利于光子集成的InP基新结构高速电光开关单元及其4x4开关阵列集成技术的研究。新型马赫-曾德开关单元由波导交汇处基于受抑全内反射原理的微纳沟槽和实现90度弯曲波导的全内反射槽构成。这一新颖集成结构不但极大减小其单片尺寸、方便器件向二维方向扩展，而且有利于降低开关功耗、提高响应速度和实现较大规模的开关阵列。本项目理论上通过导波光束在微纳沟槽边界效应的相互作用研究其受抑全内反射形成机理和采用时域有限差分法模拟古斯-汉欣位移来实现开关光学结构的设计优化，同时探索InP基亚微米和纳米尺度开口高深宽比沟槽的制备原理及技术。本项目研究为InP基光子集成回路提供了一种二维方向高度集成的新思路和新方法。

光互连相对于电互连在带宽、集成密度和功耗等诸多优势被业界认为是未来实现板间数据通信的理想方式。光互连技术中器件的高速、小型化和低功耗是集成光子学重要的发展方向。传统马赫-曾德尔电光开关及阵列由于尺寸较大或者一维方向长度过长，使得高密度光集成受到一定的限制。同时随着光电子器件的加工工艺和需求进一步朝着深亚微米和纳米尺度发展，100 nm范围孔、线、槽、柱等结构的制备是实现器件的决定性因素。本项目首先通过研究InP基材料亚波长开口宽度且深宽比高达15:1至20:1的微纳沟槽的制备工艺，掌握了基于HBr气体的100至200 nm范围开口深槽的低温刻蚀技术，其工艺条件为10 sccm流量HBr, 2 mTorr压强, 800W ICP功率, 240W Platen功率和165C温度。此关键工艺技术为深亚微米和纳米尺度光电子器件的进一步发展奠定基础。其次以此工艺基础实现的基于受抑全内反射原理的新型微纳沟槽光子耦合器，其平面尺寸与十字交叉波导面积相当，远小于Y分支、定向耦合器或者多模干涉耦合器等常规波导型光耦合器，极大地减小了由此构成的新型器件的尺寸。本项目将沟槽型光子耦合器应用到马赫-曾德尔干涉仪中，构成了高效紧凑2x2电光开关的新型结构，其尺寸约为40x40 um2。构成的高速低串扰4×4重排无阻塞型光开关阵列，其尺寸仅为340x120 um2，低于同类波导型光开关阵列器件一个数量级。此项成果缓解了传统器件在一维方向的堆积转向器件布局可以在二维方向上扩展，为InP基无源/有源光子集成电路提供了一种二维方向高度集成的新思路和新方法。最后成功实现基于金属-氧化物-半导体构成的混合表面等离激元波长尺寸电吸收型光调制器/开关。通过驱动电压控制嵌入在氧化物和半导体层之间的氧化铟锡材料的载流子浓度进而调节其光吸收系数来实现光强度调制或者开关功能。器件有效光与物质相互作用尺寸仅有几个微米长度，实测结果表明具备较低的插入损耗1.0 dB和较高的光学带宽500 nm。此项研究是对于混合表面等离激元集成技术提法的一个有效验证，具有重要理论推广和实际应用意义。