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

Optical low coherence reflectometry is applied to measure with mum pre cision the type, position and length of gratings inside a barium-titan ate crystal producing self-pumped phase conjugation. In this particula r crystal it shows the presence of an internal resonator due to reflec tions on faces of the crystal. Moreover, it was possible to measure th e simultaneous presence of transmission and reflection gratings with c onjugation efficiencies of 40% and 3%, respectively. The spectral refl ectivity of the transmission grating is Gaussian-like with a full widt h at half-maximum = 1.5 nm. The six reflection gratings, each with a l ength of 116+/-6 mum, are due to the multimode spectrum of the writing laser.