We propose and demonstrate a type of high-performance transverse magnetic (TM) multimode interferometer (MMI) in Z-cut thin film lithium niobate (TFLN). Both 1 × 2 and 4 × 4 MMI designs are demonstrated. Simulation results show that the insertion losses (ILs) are nominally about 0.157 and 0.297 dB for the 1 × 2 and 4 × 4 MMI, respectively, with wide fabrication tolerances. Based on the designed structure, the MMIs are fabricated using an argon based induced coupled plasma (ICP) etching method in Z-cut TFLN. The measured ILs are 0.268 and 0.63 dB for these two kinds of devices. The presented TM mode MMI featuring compact size and low loss can be used for both multifunctional devices and on-chip integrated circuits on a Z-cut TFLN platform.

中文翻译：

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铌酸锂薄膜中高性能多模干涉仪的设计与制造

我们提出并演示了一种在Z形切割薄膜铌酸锂（TFLN）中的高性能横向磁（TM）多模干涉仪（MMI）。演示了1×2和4×4 MMI设计。仿真结果表明，对于1×2和4×4 MMI，插入损耗（IL）的标称值分别约为0.157和0.297 dB，具有宽的制造公差。基于设计的结构，在Z形TFLN中使用基于氩的感应耦合等离子体（ICP）蚀刻方法制造MMI。对于这两种设备，测得的IL分别为0.268和0.63 dB。所呈现的TM模式MMI具有紧凑的尺寸和低损耗，可用于Z-cut TFLN平台上的多功能设备和片上集成电路。