  In the field of spin-controlled semiconductor lasers, massive effort has been
focused upon materials with long spin relaxation times (~ns). In contrast, we
demonstrate room-temperature spin-polarized ultrafast pulsed lasing in InGaAs
quantum wells (~10 ps) embedded within a GaAs microcavity. The microcavity
studied here is similar to vertical-cavity surface-emitting lasers (VCSEL) used
in optical communication. Unlike a VCSEL, the present polariton laser has
nonlinear output and energy shifts owing to the mixing of the free-carrier
polarization and cavity light field. At room temperature, we observe features
resembling those in exciton-polariton condensates at cryogenic temperatures,
including the spontaneous build-up of spatial coherence, macroscopic
occupation, and spin polarization. Our results should stimulate activities to
exploit spin-orbit interaction and many-body effects for fundamental studies of
quantum light-matter fluids and developments of spin-dependent optoelectronic
devices.
