Investigation of the pumping mechanism of the p-GE cyclotron resonance laser

An Inversion between Landau levels (LL's) of the light hole (lh) subband of germanium is achieved when the crystal is subjected to crossed electric and magnetic fields /1,2/. This leads to stimulated far infrared (FIR) emission at the cyclotron resonance (CR) frequency. The emission spectrum consists of a single line linearly tunable with magnetic field /3/. Lasing was found to depend critically on the orientation of the electric and magnetic field with respect to the crystallographic axes. Characteristically the laser emission is observed in two field regimes - which we call here low field (1) and high field (2) - depending on conditions of sample doping and external stress. In general, low concentration samples (N A − N D e 8 × 10 12 cm -3 ) oscillate in region (1) giving frequencies between 30 cm -1 and 50 cm -1 , and high concentration samples (N A − N D e 6 × 10 13 cm -3 ) oscillate in region (2) with frequencies between 65 cm -1 and 85 cm -1 . The latter samples howerver can be made to oscillate also in range (1) by applying uniaxial stress /4/.