Tensile-Strained GeSn Microbridge Lasers with Lithographically Controllable Emission Wavelengths

Abstract

GeSn alloys are considered a promising solution to long-sought on-chip industry-compatible light sources. Relentless efforts to improve the performance of GeSn lasers include utilizing tensile strain engineering. However, inducing tensile strain in GeSn has been challenging due to residual compressive strain in the GeSn layer, necessitating complex fabrication processes such as multiple deposition of external stressors. Here, we demonstrate tensile-strained GeSn microbridge lasers by harnessing a geometric strain-inversion technique enabled by a single lithography step. Multiple lasers producing different emission wavelengths were fabricated on a single chip by lithographically controlling the tensile strain. Upon the application of tensile strain, the emission wavelength was tuned by more than 45 nm, while the laser threshold was reduced by almost 70%. This work presents a simple, cost-effective way to build a large array of on-chip lasers emitting different colors. This method holds potential for applications such as wavelength division multiplexing with on-chip lasers.