Polarization dynamics of a two-photon laser

Abstract

The high degree of temporal coherence of laser light arises from a complex interplay between the fundamental light-matter interactions of absorption, spontaneous emission, and stimulated emission. The coherence properties of the generated light can be altered significantly, and often in a surprising manner, by modifying the type of light-matter interaction on which the laser is based. As an example, the two-photon laser [1,2] is based on the higher-order two-photon stimulated emission process, whereby two incident photons stimulated emission process, wherby two incident photons stimulated atom to a lower energy state and four photons are scatted, as shown schematically in Fig. 1. While replacing the standard one-photon stimulated emission process by a high-order one might be expected to give rise to subtle differences observable only at the quantum level, it has been predicted that there will be dramatic changes in both the microsopic laser behavior even when many atoms participate in the lasing process . The reason for these differences is that the two-photon stimulated emission rate depends quadratically on the incident phton flux, resulting in an inherently nonlinear light-matter interaction.