Laser Pulse Effects in Two-level Systems Driven by Coherent and Fluctuating Radiation Fields

Abstract

Abstract We reconsider the problem of a two-level system interacting with a radiation field in order to study some new features suggested by the actual experimental conditions. Pulse shape and duration effects are included in the formalism and the counter-rotating terms are retained. The criterion of validity of the rotating wave approximation (RWA) for pulsed fields is investigated; generalizing results well known in RWA, we establish some new formal results, including non-RWA contributions to all orders and for any pulse shape. The analysis is then carried out for fluctuating fields, by developing a method based on the theory of multiplicative stochastic differential equations. For short pulses, the non-Markovian character of the stochastic field parameters is expected to affect the process and, for broadband fields, the RWA has to be checked ab initio. Thus, a formalism is proposed which allows the study of both features. A wide range of numerical calculations are presented, clarifying the role of both...