Thermally induced optical bistability in CdHgTe

We report optical bistability in a room temperature, uncoated Cd_0.185Hg_0.815Te etalon using a cw CO₂ laser at 10.6 μm. The results are consistent with a band gap resonant, dispersive nonlinearity induced by a thermal shift of the band gap energy through interband and free carrier absorption. A refractive index temperature coefficient, dn/dT ～ ? 1 × 10^-3K^-1 was measured, and bistability was observed at incident powers of 20 mW.