Tuneable FIR cyclotron resonance laser in p-Ge: New aspects of the influence of the bandstructure

Abstract

p-type Germanium in crossed magnetic and electric fields is used as a continuously tuneable laser source in the far infrared. We are able to achieve laser action in a tuning range from 28 to 76 cm−1 by varying the magnetic field between 1.4 T and 3.7 T. The laser output consists of a single line having a width of 0.25 cm−1 and a maximum power of about 300 mW for a pulsewidth of 1 μsec. We compare the observed emission frequency to light hole Landau level transition energies obtained from the complete version of the Pidgeon and Brown model of the valence band, which accounts for the nonparabolicity and nonsphericity of the Γ8 valence bands in Ge. We conclude that the laser action, for B‖[110], at low magnetic fields (B < 2.7 T) is governed by the 2–3 transition in the b-set of light holes, while the action at high fields (B > 2.8 T) is governed by the light hole transition 0–1 in the same set. This agrees with estimations of the population inversion carried on within a fully quantum mechanical framework.