A Model of a Degenerate Two-Photon Amplifier

Abstract

This paper is concerned with the propagation of an electromagnetic pulse through a two-photon amplifier medium pre-pared in a state of inversion between two levels of the same parity, the carrier frequency of the incident pulse being approxi-mately one half of the atomic transition frequency. Upon neglecting competing effects which can cause emission at a frequency other than that of the incident pulse, we describe the coupled evolution of the atom-field system in terms of the usual self-consistent approach. In the coherent limit, i.e., when atomic relaxation effects are negligible, we derive an area equation for the total pulse energy, characterize the threshold condition for power amplification, and classify the multiple steady state solutions of the area equation.

After introducing incoherent atomic relaxation effects into the model, we describe the propagation of the input pulse through the amplifier with the help of a hybrid computer simulation. We analyze the transition between coherent and rate equation propagation by varying the ratio T₂/τ_p between the transverse atomic relaxation time and the pulse duration. As expected, the pulse envelope modulation and pulse break-up, which are typical manifestations of coherent interaction, gradually disappear as the rate equation limit is approached.

Work partially supported by the Army Research Office Grant number DAAG29-76-G-0075 and by the Office of Naval Research contract number N0014-76-C-1082.