Electrically Injected Exciton-Polariton Lasers.

Exciton-polaritons or polaritons, which are part-light, part-matter hybrid quasiparticles, offer an entirely new physics for realizing semiconductor lasers. These relatively new solid-state devices, which are more commonly known as polariton lasers, can generate coherent light output at two to three thousand times lower input power than that required for an equivalent photon laser. Practical applications of polariton lasers require electrically pumped devices which can operate at high temperatures, if not at room temperature. The operation of GaAs-based electrically pumped polariton lasers, which are usually designed using the vertical cavity surface emitting geometry, has remained limited to cryogenic temperatures. Though a room temperature electrically pumped polariton laser has been recently demonstrated, several important aspects and characteristics of polariton laser diodes have hitherto remained unexplored. In the present study, GaAs- and GaN-based polariton laser diodes have been experimentally realized which can operate at 155K and 300K, respectively. A novel edge-emitting device configuration, in contrast to the more commonly used surface surface-emitting one, has been employed. The polariton lasing threshold of these devices are ~20-250 times smaller than comparable conventional semiconductor photon lasers. Steady-state output polarization and small-signal modulation response of the polariton lasers have been measured and analyzed for the first time. The role of defects on the performance characteristics of polariton lasers has also been investigated and elucidated. Finally, the possibility of realizing a low power optical amplifier based on strong coupling has been studied experimentally.