Photorefractive Beam Coupling in BaTiO3

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Phase conjugation in photorefractive materials has been shown to be a useful technique for coupling two separate laser input beams(1,2). Recently Eason and Smout(2) have demonstrated that two mutually incoherent beams could be coupled in BaTiO3. We have extended these studies by carrying out beam coupling experiments in BaTiO3 designed specifically to examine phase locking and to investigate the mechanisms responsible. Our results indicate that two beams co-pump one another in a manner similar to that of self pumping for a single input beam (3). When co-pumping occurs the relative phases of the two conjugate returns are locked in phase to better than λ/10. In the co-pumping mechanism each input beam forms one of the two counter–propagating pump beams in the self-generated four wave mixing (FWM) regions. In this way each conjugate has a common phase reference (Figure 1).