# Optical Waveguide-Pair Design for CMOS-Compatible Hybrid III-V-on-Silicon Quantum Dot Lasers

## TL;DR

This paper studies the design of hybrid III-V-on-silicon lasers for efficient optical integration compatible with CMOS technology.

## Contribution

A novel epitaxial design is proposed to improve III-V/silicon optical coupling in CMOS-compatible waveguides.

## Key findings

- A 220-nm-thick silicon waveguide design enables effective III-V/Si optical coupling.
- The proposed design confines optical modes in the III-V section and transfers them efficiently to silicon.
- The design is robust to fabrication deviations.

## Abstract

The development of compact, energy-efficient integrated lasers operating at 1.3 µm re-mains a critical focus in silicon photonics, essential for advancing data communications and optical interconnect technologies. This paper presents a numerical study of distributed Bragg reflector (DBR) hybrid III-V-on-silicon lasers, analyzing design trade-offs and optimization strategies based on supermode theory. The III-V section of the design incorporates InAs/(Al)GaAs quantum dots (QDs), which offer improved temperature insensitivity at the cost of more complex III-V/Si optical coupling, due to the high refractive index of (Al)GaAs. Consequently, many current laser designs rely on silicon waveguides with a thickness exceeding 220 nm, which helps coupling but limits their compatibility with standard CMOS technologies. To address this challenge, we perform detailed simulations focusing on 220-nm-thick silicon waveguides. We first examine how the mode profiles jointly depend on the silicon waveguide dimensions and the geometry and composition of the III-V stack. Based on this analysis, we propose a novel epitaxial design that enables effective III-V/Si coupling, with the optical mode strongly confined within the III-V waveguide in the gain section and efficiently transferred to the silicon waveguide in the passive sections. Moreover, the final design is shown to be robust to fabrication-induced deviations from nominal parameters.