Fig. 2.

Concepts for on-chip silicon-based lasers using group-IV materials. a Silicon Raman racetrack ring laser Adapted with permission from [31], copyright 2022, WILEY. b Micromachining-based GOI structure realizes direct-bandgap light-emitting under tensile strain. Adapted with permission from [37], copyright 2012, NPG. c The first electrically pumped Ge laser at room temperature (combination of tensile strain and n-type doping). Adapted with permission from [38], copyright 2012, OPG. d Lasing in a direct-bandgap group IV system created by alloying GeSn without mechanically introducing strain. Adapted with permission from [40], copyright 2012, AIP. e Light emission from direct-bandgap hexagonal Ge and SiGe alloys. Adapted with permission from [26], copyright 2020, NPG