Four-photon parametric oscillation in thallium vapor

An effort was made to optimize the coherent anti-Stokes scattering four-photon parametric oscillation process in thallium vapor in the 277 nm range. The dependence of the stimulated emission power on the thallium vapor pressure, confocal parameter, detuning from two-photon resonance, and pump power was investigated. The considerable saturation of the parametric oscillation power observed both with respect to the pump power and the vapor pressure was attributed to the breakdown of the wave interaction as a result of the strong high-frequency Kerr effect under two-photon resonance conditions.