Phase conjugation of a speckle-inhomogeneous beam by an Nd glass oscillator based on four-wave mixing with feedback

A study is reported of a system, making use of four-wave mixing with feedback (FWMF), for high-quality phase conjugation of speckle-inhomogeneous radiation. The system includes a hologram formed on the basis of nonlinearity of gain saturation. A theoretical analysis is made of selective capabilities of a ‘short’ hologram, whose length is less than the longitudinal correlation lengths of the ‘write’ waves used to form it. The statistical-average values of the parameters of modes in an FWMF cavity are determined. The experimental results obtained for a neodymium glass system show that the fidelity of phase conjugation of speckle beams with a divergence (5 — 25)θ_diffr is 80%. The maximum energy of the phase-conjugated component is 0.35 J and the maximum energy reflection coefficient of an FWMF mirror is 20.