Laser Beam Coupling via Optical Phase Conjugation in BaTiO3

Abstract : The nonlinear crystal barium titanate was used to couple mutually incoherent argon-ion laser beams using a co-pumped four-wave mixing mechanism which transfers photons from each beam into the phase-conjugate outputs of the others. The four-wave mixing geometry which was used has been described in the literature as the mutually incoherent beam coupler. The beams, all incident on the same crystal a face, form coupling loops as they internally reflect into each other at the opposite crystal corner. Coupling between two and three beams was investigated. Coupling between two beams resulted in phase-conjugate returns which were both self-pumped and co-pumped. Reflectivities of 9% to 42% were obtained for all angles of incidence greater than 50 degrees. (The angle between beams was less than 7 degrees). Keywords: Phase conjugation, Barium titanate, Four-wave mixing, Laser beams, Coupling, Theses.