High-Performance Silicon MMI Switch Based on Thermo-Optic Control of Interference Modes

Abstract

We demonstrate a compact and high-performance $1\times 2$ silicon MMI switch by thermo-optic control of symmetric interference modes using local and direct heating of the mode-peak regions. The direct heater is formed with n-i-n-i-n resistors whose $i$ -regions are placed at the peak regions of the first two-folded image. Three electrodes are separately formed on each $n$ -doped region for alternative heating of the two $i$ -regions. Using a symmetric $1\times 2$ MMI designed as a 50:50 splitter under no bias, path switching is attained by inducing a phase difference of ± $\pi$ /2 between the two modes, applying a bias to either n-i-n heater. From this switching scheme, we achieve a low crosstalk of less than −30 dB with a compact active area of 3 $\mu \text{m}\times40~\mu \text{m}$ . We also observe a fast switching response with a rising time of $1.04~\mu \text{s}$ and a falling time of $0.89~\mu \text{s}$ .