Band-To-Band Optical Pumping in Solids and Polarized Photoluminescence

Band-to-band optical pumping of spin-polarized conduction electrons is demonstrated in $p$-type GaSb at 4.2°K by measurement of the degree of polarization of the photoluminescence. Significant electronic polarization [42 (±8)%] is achieved, and experiments with a weak transverse magnetic field yield the electronic lifetime $\tau =6.0(\pm 0.7)\times {10}^{-9\mathrm{}}$ sec of the photocreated electrons.