Mode Splitter Without Changing the Mode Order in SOI Waveguide

Abstract

We proposed a mode splitter based on directional coupler (DC), which is capable of splitting the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> modes without changing the mode order. It is found that high coupling efficiency (higher than -1 dB), low mode crosstalk (less than -16 dB), wide bandwidth (~100 nm), and large fabrication tolerance (±10 nm) can be obtained by a 24.4 μm coupling length DC structure, which is composed of a strip and a slot silicon waveguide. This design represents a first step toward mode splitter without changing the mode order, which can find important potential applications, such as optical isolation and mode division multiplexing (MDM), in large-scale photonic integrated circuits (PICs).