Vertical Injection and Wideband Grating Coupler Based on Asymmetric Grating Trenches

TL;DR

This paper presents a novel silicon-on-insulator vertical fiber-to-chip grating coupler utilizing engineered subwavelength structures to achieve high directionality, efficiency, and bandwidth through asymmetric diffraction and effective index variation.

Contribution

The paper introduces a new design of a vertical grating coupler based on asymmetric gratings and subwavelength structures, enhancing coupling efficiency and bandwidth.

Findings

Achieves 76% coupling efficiency

Provides 39 nm 1-dB bandwidth

Uses 2D FDTD for analysis

Abstract

A Silicon-on-insulator (SOI) perfectly vertical fibre-to-chip grating coupler is proposed and designed based on engineered subwavelength structures. The high directionality of the coupler is achieved by implementing step gratings to realize asymmetric diffraction and by applying effective index variation with auxiliary ultra-subwavelength gratings. The proposed structure is numerically analysed by using two-dimensional Finite Difference Time Domain (2D FDTD) method and achieves 76% (-1.19 dB) coupling efficiency and 39 nm 1-dB bandwidth.