1D Photonic Crystal GeSn-on-Insulator Nanobeam Laser

Abstract

A CMOS-compatible light source has long been pursued to realize photonic-integrated circuits. Relentless efforts have been made to realize Ge-based lasers with various methods including heavy n-type doping and mechanical tensile strain. Recently, GeSn alloys have emerged as a promising material for realizing a CMOS-compatible laser. However, the GeSn lasers reported to date have large device footprints and active areas, which limit achieving high-density integration of lasers and energy-efficient lasers, respectively. 1D photonic crystal nanocavities may provide new opportunities to achieve densely integrated GeSn lasers operating at extremely low power consumption owing to their intrinsically small device footprints and active areas. However, there has been no demonstration of a 1D photonic crystal laser in GeSn. Here, we demonstrate a 1D photonic crystal nanobeam GeSn-on-insulator laser that achieves a very small device footprint (similar to 7 mu m(2)) and a compact active area of similar to 1.2 mu m(2). We also improved the lasing characteristics in our nanobeam lasers in terms of the threshold and operating temperature by releasing the harmful compressive strain while offering adequate thermal management and strong optical confinement simultaneously. The strain-free nanobeam showed a lower threshold of similar to 18.2 kW cm(-2) at 4 K compared to the compressively strained counterparts (similar to 38.4 kW cm(-2) at 4 K). The strain-free nanobeam showed clear lasing up to 90 K, whereas the compressively strained nanobeam only shows a broad spontaneous emission spectrum at a temperature of 70 K. Our demonstration paves the way toward CMOS-compatible lasers with high-density integration and low-power consumption.