Time, space, and spectral multiplexing for radiation balanced operation of semiconductor lasers

Radiation balanced lasing (RBL) is an attractive pathway towards the development of high power and good beam quality lasers because heat removal via anti-Stokes luminescence (optical refrigeration) does not require additional connections and components and the heat is dissipated away from the active medium. Optical refrigeration had been demonstrated in the rare-earth doped laser medium but is far more difficult to achieve it in semiconductors laser medium. The main obstacle to achieve RBL in semiconductors is that the most efficient cooling occurs at relatively low carrier densities, while the gain required to sustain laser operation occurs at much higher densities. In this study, we explore the means of resolving this conundrum by separating the optical refrigeration and lasing in temporal, spatial, and/or spectral domains. Time multiplexing involves modulating the pump and operating the laser in pulse modes with lasing and cooling intervals. Space multiplexing involves having separate regions (quantum wells and dots) for lasing and cooling. The spectral multiplexing involves operating with two separate pumps - one for lasing and one for cooling. These methods will be compared in the study with the goal of selecting the optimal path RBL in semiconductor lasers.