Compact light couplers for lateral III–V membrane devices grown on SOI platforms

Abstract

Compact light couplers between III–V devices and Si waveguides are crucial for advancing the scalability of Si photonics. Here, we present a compact light coupling strategy for lateral III–V membrane lasers and PDs directly grown on SOI platforms. Benefiting from the coplanar configuration of epitaxial III–V membranes and Si device layer, we designed novel, to our knowledge, butt couplers to achieve both small footprint and high efficiency coupling. We employed sub-wavelength grating structures to gradually bridge the effective refractive index between the III–V membranes and Si waveguide and obtained a coupling loss of less than 0.5 dB across the entire telecom band in a length of less than 10 μm. Our work here offers a fresh perspective for future densely integrated Si photonics.