Frequency Shifts Of Self-Pumped Phase Conjugators

Abstract

The reflection from most photorefractive, self-pumped phase conjugators differs in frequency from the incident beam by a small amount (Δω/ω ≈ 10^-15). A theory and the supporting experiments which explain such frequency shifts are presented. In our theory, four-wave mixing is responsible for the generation of the conjugated wave where a self-oscillation arising from photorefractive coupling provides the customary pumping beams. The frequency of these pumping beams is determined by a resonance cavity geometry and may be slightly different from that of the incident beam. Nondegenerate four-wave mixing using these self-oscillating pumping beams give rise to the frequency shift of the phase-conjugate reflection. Experimental results are in good agreement with theory.