On-Chip High Extinction Ratio Single-Stage Mach-Zehnder Interferometer based on Multimode Interferometer

TL;DR

This paper presents a novel single-stage on-chip Mach-Zehnder interferometer with a record high extinction ratio of 61.2 dB, achieved by using cascaded multimode interferometers and a bend-based TM filter to suppress noise.

Contribution

The study introduces a high extinction ratio single-stage MZI based on cascaded MMIs and a TM filter, surpassing previous multi-stage approaches in performance.

Findings

Achieved a 61.2 dB extinction ratio in a single-stage MZI.

Implemented a bend-based TM filter to suppress TM noise.

Demonstrated thermal tunability with low insertion loss and wide bandwidth.

Abstract

On-chip high extinction ratio Mach-Zehnder interferometers (MZI) have always attracted interest from researchers as it can be used in many applications in astrophotonics, optical switching, programmable photonic circuits, and quantum information. However, in previous research studies, ultra-high extinction ratio on-chip MZIs have only been achieved by using a multi-stage MZI approach. In this paper, we investigate a high extinction ratio single-stage MZI based on two cascaded multimode interferometers (MMI). We determine that TM noise is an important factor that can prevent us from achieving a high extinction ratio MZI. By introducing a bend-based TM filter without additional loss, we experimentally demonstrate that such a TM filter can improve the maximum extinction ratio of the MMI-MZI by more than 10 dB. With the TM filter, we report a record high 61.2 dB extinction ratio in a single stage, thermally tunable MMI-MZI with only 1.5 dB insertion loss and more than 60nm bandwidth. These results pave the way for many interesting applications.