Towards room temperature polariton amplification in semiconductor microcavities

Summary form only given. We show that engineering the sample structure and constituent materials in order to maximize the exciton-photon coupling greatly improves the gain of the amplifier and its operating temperature. We set-up an angle-resolved pump-probe experiment in the reflection geometry, shining on to the sample 250 fs long pulses from a titanium doped sapphire laser. We report peak gain on the weak probe beam of up to 5000 in GaAs-based microcavities and demonstrate that the stimulation effect survives above liquid nitrogen temperatures, up to 120 K.