Influence of impurities on broadbandp-type-Ge laser spectra under uniaxial stress

We have investigated the stimulated emission of a broadband p-type-Ge laser (light- to heavy-hole laser) with uniaxial stress up to 500 bars. The emission spectra can be divided into two ranges, the low- and the high-frequency ranges. Between these ranges a region without emission occurs (emission gap) which is explained by impurity absorption. This emission gap vanishes for stress values larger than 400 bars. The structure of the stimulated emission in the low-frequency range is explained by impurity absorption lines. The spectral features of the stimulated emission in the high-frequency range with applied stress suggest that the emission of the p-type-Ge laser is not caused by transitions between the light- and the heavy-hole subbands. Rather, the emission is generated by optical transitions between Landau levels of the light holes and excited impurity states.