Electrically pumped terahertz SASER device using a weakly coupled AlAs/GaAs superlattice as the gain medium

We describe an electrically pumped sound amplification by stimulated emission of radiation (SASER) device for terahertz frequencies. The gain medium of the device is a weakly coupled AlAs/GaAs superlattice (SL). It is incorporated into a multimode acoustic cavity formed between the top (free) surface of the structure and a second SL acting as a phonon reflector. We report measurements on a prototype device using bolometers to detect the emitted phonons. An enhancement of the phonon emission parallel to the SL growth direction is observed when the energy drop per period of the gain SL matched the cavity phonon energy. This was accompanied by a small increase in device current. We argue that these results provide evidence that the device is operating as a SASER.