Observation of amplified reflection through degenerate fourwave mixing at CO(2) laser wavelengths in germanium

We report the first known observation of amplified reflection through degenerate four-wave mixing at 10.6 microm. Reflectivities of over 100% are reported in both n-type and p-type germanium at pump intensities of about 100 MW/cm(2). The maximum reflectivity reported is 800% in p-type Ge.