About the Atomic Correlation Functions in Higher Order Coherence

C. L. Mehta, L. Mandeļ

Andrei N. Weiszmann

The concept of coherence is analyzed in a system of interacting radiation and matter. Using the projection technique, the reduced field density operator is found, and with it the first and higher order field correlation functions are computed. It is proved that the inelastically scattered field is, for the most part, incoherent in any order at any time interval after collision with an atomic ensemble, except some specific time intervals and positions, where the order of coherence is determined by the atomic correlations considered.

Ravinder Nath

Andrei N. Weiszmann

Considering the coherence properties of an inelastically scattered quantum radiation by an ensemble of N identical three level atoms in a solid-like array, we addressed the question whether this process is actually mediated by a series of multipole interactions and/or a series of virtual intermediate-exciton transitions and how the type of the considered mediation is reflected in the higher order coherence properties of the scattered radiation. Using a projector technique the reduced field density operator, the atomic and field correlation functions were found, the higher order coherence properties were studied and the arrival-time and phase correlation conditions of the light quanta were obtained and analysed. The results suggest that not only the arrival-time and phase correlation conditions are mathematically independent from the type of the considered mediating process, but that the multipole interaction approximation of a resonant Raman scattering, in the above considered system, is physically equivalent with the virtual intermediate-exciton transitions too.

Ravinder Nath, Pradumn Kumar

G. S. Agarwal, E. Wolf

Some years ago a new coherence theory in the space-frequency domain was formulated. Subsequent research has revealed some difficulties regarding the representation, in this theory, of the higher-order correlation functions. In the present paper the origin of these difficulties is discussed and a new representation of the higher-order correlation functions is introduced, in terms of the coherent modes of the second-order theory.