Stimulated emission from p-Ge due to transitions between light-hole Landau levels and excited states of shallow impurities

We investigate the far infrared emission spectra obtained from the so-called p-Ge light-heavy-hole laser. The occurrence of a frequency gap between the observed low-frequency and high-frequency range is for the first time explained by self-absorption due to impurity transitions. In the high-frequency range we find evidence of transitions between light-hole Landau levels and excited states of shallow impurities to be responsible for the lasing transitions.