Theory of a transient opposed four-wave interaction in resonant media subjected to fields of arbitrary intensity

A theory is developed of an opposed degenerate four-wave interaction in resonant two-level media subjected to fields of arbitrary intensity. An allowance is made for the transient nature of the response of a relaxing medium. An infinite chain of equations is used to describe the interaction in such fields, the cases of steady-state and transient interactions are discussed separately, and the results of numerical calculations illustrating the theory are given. It is shown that in the steady-state case the equations derived in the present study reduce directly to the familiar equations of a small-signal theory. A qualitative analysis of the equations for the transient degenerate four-wave interaction shows clearly that in strong fields this interaction may be more effective than the steady-state interaction.