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

GeSn alloys have been regarded as a potential lasing material for a complementary metal–oxide–semiconductor-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 nanobeam with a very small device footprint of 7 μm2 and a compact active area of ∼1.2 μm2 on a high-quality GeSn-on-insulator 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 quenching of lasing at a temperature of 70 K. Our demonstration offers an avenue toward developing practical group-IV light sources with high-density integration and low power consumption.