高速光开关是实现光传输路径变换的关键器件之一. 对于目前马赫-曾德型光开关本身占据的尺寸较大或者在一维方向上尺度较长的缺点, 提出了一种利于高度集成的矩形马赫-曾德2×2光开关单元结构. 器件由基于受抑全内反射原理的沟槽型微纳分光/合光器和90°弯曲波导的L型参考/相移臂两者构成, 极大地减小了由此构成的马赫-曾德光开关器件的尺寸. 利用硅的热光效应, 举例设计了开关器件的L型相移臂上升50℃实现π相移时需要的总长度约为84 μm. 同时采用有限元法分析得到在NiCr金属电极加热器上施加电压3.5 V时, 可以使相移臂内的脊波导层上升温度约为50℃; 模拟了介质覆盖上包层不同SiO2厚度时的时间响应特性, 选用上包层SiO2厚度为0.5 μm时得到器件上升时间35 μs、下降时间48 μs的开关速度. 最后使用Rsoft FullWAVE软件模块时域有限差分法仿真验证了热光开关器件的开关功能. 设计的硅基矩形结构马赫-曾德2×2热光开关的平面尺寸为56×38 μm2. 器件具有高效紧凑的特点, 使其布局配置易于向二维方向扩展, 并潜在应用于硅基高密度光子集成回路及片上光互连系统.

High speed optical switches are critical components in the realization of light transmission path switching technology for optical networks. Current Mach-Zehnder Interferometer type optical switches either occupy larger footprint or have a longer one-dimensional scale. A Silicon-based rectangular Mach-Zehnder 2×2 thermo-optical switch unit is proposed for the highly integrated applications. The novel optical switch consists of trench-based nanophotonic frustrated total internal reflection couplers and total internal reflection mirror-based 90° waveguide bends. The switching operation is achieved through thermo-optical effect of Silicon. As a design example, the ~84 μm long L-shape phase-shifting arm is determined for π phase shift when its temperature of the arm is increased up to 50℃. A switching voltage of 3.5 V on a NiCr metal electrode heater is obtained by using finite element method. The voltage may lead to the increase of 50℃ for an optical ridge waveguide in the L-shape phase-shifting arm. The time response of the device is simulated as a function of different upper dielectric thickness of SiO2, and the response time including raise time of 35 μs and fall time of 48 μs is optimized for the device with 0.5 μm thickness of upper SiO2. The switching function of the thermo-optical switch is simulated and verified by Rsoft FullWAVE software, a finite difference time domain method. The chip size of 56×38 μm2 is designed for the Silicon-based rectangular Mach-Zehnder 2×2 optical switch. The device is ultra-compact, and its configuration is beneficial to extend at two-dimensional directions, making them attractive for Silicon-based high dense photonic integrated circuits and on-chip optical interconnect system.