Optically pumped intersubband laser: Resonance positions and many-body effects

Intersubband transition (IT) between confined states in quantum wells (QW's) is a fully collective phenomenon displaying distinct many-body effects. These effects are seen in an optically pumped ITQW laser. The strong pump, needed to achieve population inversion, ``undresses'' the depolarization effect, leading to a redshift in the absorption peak position. The emission wavelength is also redshifted due to a combination of Hartree, exchange-correlation, and depolarization effects. The depolarization shift is in the opposite direction for the emission between population inverted levels than for the usual absorption case.