Phase-conjugation property of one-photon pumped backward stimulated emission from a lasing medium

Optical phase-conjugation properties of the backward stimulated radiation from a one-photon pumped lasing medium have been studied. The gain medium is a dye solution (pyrromethene 597 in ethanol) or the same dye doped poly(methyl methacrylate) (PMMA) rod pumped with ∼7-ns and 532-nm laser pulses. A highly directional and phase-conjugate backward stimulated emission at ∼573 nm wavelength could be obtained with a conversion efficiency of ∼42% by using a 1-cm-long dye solution sample at the concentration level of d₀= 0.000 15 mol/L. The spectral, temporal, output/input, and phase-conjugation properties of this backward stimulated emission are presented in detail. The induced aberration influence, which is much larger than the divergence angle of the input pump beam, can be basically removed by the backward stimulated emission; however, the fidelity of the near-field detail for the backward stimulated emission is relatively poor. A quasi-collinear holographic interaction model and a mathematical analysis are presented to explain the basic experimental results.