Absorption of СО2 laser radiation by photocarriers in a germanium crystal

The absorption of СО₂ laser radiation in a germanium crystal, excited previously by a pulse from an Nd laser, was investigated experimentally and numerically. An analytic dependence of the optical transmission coefficient on the intensity of the exciting radiation was derived for a semiconductor in its transparency range. This analytic dependence was in good agreement with the experimental data obtained for a germanium crystal in the investigated range (of practical importance) of the photoexcitation rates. A high density of free carriers in photoexcited germanium demonstrated that this material is suitable for modulators of СО₂ laser radiation.