High-efficiency grating couplers for pixel-level flat-top beam generation

TL;DR

This paper presents a novel silicon-based grating coupler design that efficiently generates high-quality flat-top beams with small pixel-level size from photonic integrated circuits, suitable for free-space applications.

Contribution

The paper introduces a dual-etch grating and Bragg reflector design enabling pixel-level flat-top beam generation with high efficiency and mode matching on silicon photonic chips.

Findings

Achieved 6.6 um pixel-level flat-top beam with -0.5 dB vertical radiation

Mode match of 97% at 1550 nm wavelength

Designed multiple high-efficiency couplers for various beam scales

Abstract

We demonstrate a kind of grating coupler that generates high quality flat-top beam with a small beamwidth from photonic integrated circuits into free-space. The grating coupler is designed on a silicon-on-insulator wafer with a 220 nm-thick silicon layer and consists of a dual-etch grating (DG) and a distributed Bragg reflector (DBR). By adjusting the structural parameters of DG and DBR, a pixel-level (6.6 um) flat-top beam with the vertical radiation of -0.5 dB and the mode match of 97% at 1550 nm is realized. Furthermore, a series of high-efficiency grating couplers are designed to create flat-top beam with different scales.