Low-power nonlinear Fabry-Perot reflection in CdHgTe at 10 µm

Measurements of the intensity dependence of CO
2
laser radiation reflected from a polished Cd
0.23
Hg
0.77
Te etalon at 77 K results in nonlinear features at power levels on the order of 1 mW, in good agreement with a theory which includes bandgap resonant nonlinearities and Auger carrier recombination. A high-reflectivity rear coating enhances these features, giving a characteristic which demonstrates differential optical gain. The effects of heating are discussed in this unusual case in which the electronic and thermal contributions to the intensity dependence have the same sign.