Physical origin of laser frequency scanning induced by photorefractive phase-conjugate feedback

Abstract

We present numerical simulations of the complex grating structure that is generated when several longitudinal modes from a laser induce a self-pumped phase conjugator in a photorefractive barium titanate crystal. The results of the numerical analysis clearly show that the detuning curve of the generated grating structure is asymmetric with respect to the center wavelength of the laser that induced it. The asymmetric feedback to the laser, which is generated by diffraction in the gratings of the structure, initiates the frequency scanning of the laser. It is found that the material frequency dispersion of the barium titanate crystal causes the asymmetry and is the origin that initiates the scanning process. The theoretical predictions are in agreement with the reported experimental observations.