1D photonic crystal direct bandgap GeSn-on-insulator laser

TL;DR

This paper demonstrates a highly compact GeSn-on-insulator nanobeam laser with improved efficiency and higher operational temperature, enabling dense integration of low-power, CMOS-compatible on-chip light sources.

Contribution

It introduces a 1D photonic crystal nanobeam laser with a small footprint and active area on GeSnOI, showing enhanced directness, lower threshold, and higher temperature operation compared to previous GeSn lasers.

Findings

Threshold density of 18.2 kW/cm² at 4 K

Lasing persists up to 90 K

Compact device footprint of 7 μm²

Abstract

GeSn alloys have been regarded as a potential lasing material for a complementary metal-oxide-semiconductor (CMOS)-compatible light source. Despite their remarkable progress, all GeSn lasers reported to date have large device footprints and active areas, which prevent the realization of densely integrated on-chip lasers operating at low power consumption. Here, we present a 1D photonic crystal (PC) nanobeam with a very small device footprint of 7 ${\mu}m^2$ and a compact active area of ~1.2 ${\mu}m^2$ on a high-quality GeSn-on-insulator (GeSnOI) substrate. We also report that the improved directness in our strain-free nanobeam lasers leads to a lower threshold density and a higher operating temperature compared to the compressive strained counterparts. The threshold density of the strain-free nanobeam laser is ~18.2 kW cm$^{ -2}$ at 4 K, which is significantly lower than that of the unreleased nanobeam laser (~38.4 kW cm$^{ -2}$ at 4 K). Lasing in the strain-free nanobeam device persists up to 90 K, whereas the unreleased nanobeam shows a quenching of the lasing at a temperature of 70 K. Our demonstration offers a new avenue towards developing practical group-IV light sources with high-density integration and low power consumption.