Optically induced intervalence-band transitions in germanium by the absorption of 1.06 μm picosecond pulses

The intervalence-band adsorption coefficient in germanium is calculated as a function of the hole density and temperature for light with a wavelength of 1.06 μm. This adsorption mechanism is normally negligible compared to the interband absorption; however, for a sufficiently dense electron-hole plasma, the free-hole intervalence-band adsorption can become comparable to the interband adsorption. Furthermore, the interaction of intense 1.06 μm light can alter the distribution of resonantly-coupled hole states and lead to an intensity dependence in the intervalence-band absorption cross section. For a fixed hole density, the intervalence-band cross sections due to free-hole transitions between the heavy- and split-off hole bands and between the light- and split-off hole bands are found to decrease with increasing intensity in a manner closely approximated by an inhomogeneously broadened two-level model. Values for the saturation intensity of each resonant transition are calculated as a function of the hole density and temperature. The intensities required to begin to saturate the direct free-hole transitions are easily attainable using picosecond pulses. 31 references, 4 figures