Opt Lett. 2014 Jan 15;39(2):259-62. doi: 10.1364/OL.39.000259.
A novel polarization beam splitter (PBS) with an extremely small footprint is proposed based on a multimode interference (MMI) coupler with a silicon hybrid plasmonic waveguide. The MMI section, covered with a metal strip partially, is designed to achieve mirror imaging for TE polarization. On the other hand, for TM polarization, there is almost no MMI effect since the higher-order TM modes are hardly excited due to the hybrid plasmonic effect. With this design, the whole PBS including the 1.1 μm long MMI section as well as the output section has a footprint as small as ∼1.8 μm×2.5 μm. Besides, the fabrication process is simple since the waveguide dimension is relatively large (e.g., the input/output waveguides widths w ≥300 nm and the MMI width w(MMI)=800 nm). Numerical simulations show that the designed PBS has a broad band of ∼80 nm for an ER >10 dB as well as a large fabrication tolerance to allow a silicon core width variation of -30 nm<Δw<50 nm and a metal strip width variation of -200 nm<Δw(m)<0.
提出了一种基于具有硅混合等离子体波导的多模干涉（MMI）耦合器的新型小尺寸偏振分束器（PBS）。部分覆盖金属条的 MMI 部分设计用于实现 TE 偏振的镜像成像。另一方面，对于 TM 偏振，由于混合等离子体效应几乎不会激发高阶 TM 模式，因此几乎没有 MMI 效应。通过这种设计，整个 PBS 包括 1.1μm 长的 MMI 部分以及输出部分，其足迹小至约 1.8μm×2.5μm。此外，由于波导尺寸相对较大（例如，输入/输出波导宽度 w≥300nm 且 MMI 宽度 w（MMI）=800nm），制造工艺简单。数值模拟表明，设计的 PBS 在 ER>10dB 时具有较宽的带宽约为 80nm，并且具有较大的制造容差，允许硅芯宽度变化为-30nm<Δw<50nm 以及金属条宽度变化为-200nm<Δw（m）<0。
