Phase conjugation of CO2 laser radiation in a mediumwith thermal nonlinearity

An investigation of reflectivity and quality of phase conjugation of CO₂ laser radiation by four-wave mixing in a medium with thermal nonlinearity is discussed. High reflectivity produced by four-wave mixing in CCl₄ was demonstrated both for pulsed radiation (180%) and for CW radiation (20%). A self-pumped phase-conjugate mirror based on four-wave mixing with feedback was realized. Energy, spatial, spectral, temporal, and polarization characteristics of radiation generated by four-wave mixing with feedback in CCl₄ were investigated. The minimum threshold energy of the input signal was ≃8 mJ; the maximum energy reflectivity was about 5. The spatial structure of radiation generated in the scheme of four-wave mixing with feedback was investigated theoretically, and the conditions for phase conjugation, both for regular and for speckled signal beams, were determined