CHARACTERIZATION OF A PHOTOREFRACTIVE PHASE CONJUGATOR BY OPTICAL LOW-COHERENCE REFLECTOMETRY

Optical low coherence reflectometry is applied to measure with mum precision the type, position and length of gratings inside a barium-titanate crystal producing self-pumped phase conjugation. In this particular crystal it shows the presence of an internal resonator due to reflections on faces of the crystal. Moreover, it was possible to measure the simultaneous presence of transmission and reflection gratings with conjugation efficiencies of 40% and 3%, respectively. The spectral reflectivity of the transmission grating is Gaussian-like with a full width at half-maximum = 1.5 nm. The six reflection gratings, each with a length of 116+/-6 mum, are due to the multimode spectrum of the writing laser.