Measurement of optical two-photon gain in electrically pumped AlGaAs at room temperature

We demonstrate experimentally two-photon gain in semiconductor structures, shown previously only in dilute atomic systems. Two-photon gain is directly observed and characterized in electrically pumped room-temperature semiconductor devices, in good agreement with theory. The semiconductor structure was designed to enhance the two-photon interaction and reduce parasitic effects. The nonlinear two-photon amplification is studied directly by examining the current dependence of the optical intensity growth, and indirectly by monitoring the reduction in one-photon emission due to two-photon transitions above transparency.