Time-delayed four-wave mixing: the interplay between laser field fluctuations and the atomic memory time

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Description/Abstract

Coherent signals induced by fundamentally incoherent phenomena through a four-wave mixing process are among the most intriguing and subtle effects in nonlinear spectroscopy. These effects were initially observed by Bloembergen and his co-workers in the form of pressure-induced extra resonances in four-wave mixing. Using standard perturbance techniques based on the optical Bloch equations, they suggested that these collision induced resonances were the result of a "destruction of the destructive interference" existent between two alternate time-ordered pathways. Subsequently, Prior et al realised that fluctuations in the incident radiation fields could play essentially the same role as the collisionally induced dephasing. In practice, of course, both collisional dephasing and field fluctuations are present in a typical atomic vapor pulsed four-wave mixing experiment. If the timescales governing these two effects approach one another, one can expect to gain valuable new insight into this fascinating process of "incoherently" inducing a coherent signal