Germanium microlasers on metallic pedestals

TLDR: In this paper, a tensile-strained germanium microdisks have been fabricated with metallic pedestals, and the transferred tensile strain leads to a thin film with a direct bandgap.

Abstract: Strain engineering is a powerful approach in micro- and optoelectronics to enhance carrier mobility, tune the bandgap of heterostructures, or break lattice symmetry for nonlinear optics. The dielectric stressors and bonding interfaces used for strain engineering in photonics can however limit thermal dissipation and the maximum operation temperature of devices. We demonstrate a new approach for enhanced thermal dissipation with stressor layers by combining metals and dielectrics. The method is applied to the germanium semiconductor. All-around tensile-strained germanium microdisks have been fabricated with metallic pedestals. The transferred tensile strain leads to a germanium thin film with a direct bandgap. Under continuous wave optical pumping, the emission of the whispering gallery modes is characterized by a threshold and an abrupt linewidth narrowing by a factor larger than 2. The occurrence of stimulated emission is corroborated by modeling of the optical gain. This demonstrates lasing with pure germanium microdisks.