Broadband modulation of 3-µm light by 10-µm light in p-germanium

High-power CO
2
laser radiation at 1045 cm
^-1
is shown to enhance the room temperature transmission of p-Ge in a spectral region extending at least from 3000 to 4000 cm
^-1
. The interaction arises from radiation-induced changes of the hole populations within the three valence bands. Ultrafast nonradiative relaxation is responsible for the very large interaction bandwidth observed and allows the prediction of a minimum switching time of 1 ps.