Design of a waveguide-coupled GeSn disk laser

TL;DR

This paper presents a novel waveguide-coupled GeSn microdisk laser design that efficiently transfers optical power and achieves high outcoupling efficiency in a compact geometry, advancing integrated photonics.

Contribution

It introduces a new design leveraging the GeSn virtual substrate for both laser cavity and waveguides, with mode engineering to enhance power transfer and efficiency.

Findings

Waveguide outcoupling efficiency up to 27%

42% of optical power recycled in the laser cavity

Compact 7 μm radius resonator demonstrated

Abstract

We report on the design of a waveguide coupled GeSn microdisk-laser cavity in which the germanium virtual substrate serving as a template for GeSn growth is repurposed for the definition of passive on-chip interconnection waveguides. A main challenge resides in transferring the optical power from the upper (Si)GeSn gain stack to the underlying virtual substrate layer and is solved with laser mode engineering. Designs are based on experimentally realized layer stacks and waveguide outcoupling efficiencies as high as 27% are shown in compact resonator geometries with a small, 7 $\mu$m radius, with 42% of the power being recycled in the laser cavity.