Photon avalanche effect in doped quantum wells

A system of n-doped quantum wells is considered. The system is illuminated by IR radiation with frequency ω resonant to the transition between the second and third size-quantized subbands. At low light intensities j, the excitation does not induce any intersubband transitions. At higher j, however, a photon avalanche process can develop due to Auger-like transitions. The threshold light intensities for the effect, jth, are tens or hundreds of kW/cm2. The equilibration times of the effect, τeq, are extremely short: τeq∼10–100 ps. The energy necessary for ultrafast switching between the states, when the second and third subbands are empty or populated, can be estimated at 10–100 fJ/μm2.