Anomalous coherence functions of the radiation fields

Abstract

The anomalous coherence functions (ACF) of the radiation fields are studied in detail. The relation of ACF to the source correlation functions is given. Propagation laws for ACF are found. The ACF exhibit a diffractionlike pattern, the nature of which depends on the directions of observation and the spatial extent and initial excitation of the source. If the radiating system is incoherently excited, then ACF vanish. However for any arbitrary system driven by a coherent field ACF are found to be nonzero. ACF are shown to contain information both on the steady-state and transient response of the radiating system. Quantum fluctuations are shown to be important for ACF even when the system is weakly driven, which is in contrast to the ACF for the harmonic oscillator which can be obtained from classical considerations. ACF are also shown to exist in the nonlinear mixing of the electromagnetic fields. The possibility of measuring anomalous coherence functions using phase-conjugation techniques is discussed.