Implementation of Tapered Multimode Interference Lightwave Combiner on Silicon-on-Insulator Substrate with Negligible Back-Reflection

Abstract

We fabricated and experimentally evaluated 2×1 tapered multimode interference (MMI) combiners on silicon-on-insulator (SOI) substrates. The tapered MMI combiner we previously proposed is expected to be free from the reflection problem usually existed in a conventional rectangular MMI coupler, and such a negligible back-reflection property was actually verified. As one of its applications, we implemented a Mach–Zehnder (MZ) modulator using the tapered MMI combiner, which is often equipped with semiconductor optical amplifiers (SOAs) for ultrahigh-speed photonic switching devices and those SOAs are quite sensitive to the back-reflection.