Temperature effects in photodetection

We present a theoretical study of photodetection with coupling of the photosensitive atoms to a reservoir. We investigate the effects of nonzero detector temperature, where the initial thermal-equilibrium occupation of the atomic levels and the thermalization of the radiation field interfere with the measurement of the photon statistics. We derive formulas exhibiting the temperature dependence of the field dynamics, the relationship between field and atomic moments, and the photocounting probability. We present examples illustrating how the coherence properties of the incoming field are affected by the detection process in the presence of thermal noise.