Multiple-beam, spatially mode-locked photorefractive oscillator

Abstract : Mutual locking of four Gaussian beams with prescribed relative amplitudes and phases in a resonator ended by a phase-conjugating mirror is shown. Locking is performed thanks to a pair of mutually matched spatial filters located in the Fourier planes of the resonator. Experimental results are obtained in a cw-oscillator using a barium titanate crystal both as phase-conjugating mirror and amplifying medium.