Many-photon processes with the participation of squeezed light

Abstract

The description of an electromagnetic field of complicated statistics with noise, coherent, and squeezed features are discussed using the nondiagonal coherent-state representation of the density matrix and the normally ordered characteristic function derived therefrom. The quantity 〈($a^{\mathrm{°}}$ ${)}^n$ $a^n$〉 which plays a central role in the theory of many-photon processes is found for this field. Particular cases with dominant coherent signal, noise, or squeezing are discussed. It is found that the ratios 〈($a^{\mathrm{°}}$ ${)}^n$ $a^n$〉/(〈$a^{\mathrm{°}}$a〉${)}^n$ for the coherent, the chaotic, and the strongly squeezed vacuum states are 1, n!, and (2n-1)!!, respectively. The value of 〈($a^{\mathrm{°}}$ ${)}^n$〉 related to the anomalous coherence function is considered. It is found that the noise does not influence 〈($a^{\mathrm{°}}$ ${)}^n$〉.