Abstract

Nonlinear optical phase conjugation in photorefractive crystals and other dynamic recording media have generated tremendous interest because of potential applications in restoration of distorted images. Self-pumped phase conjugation has been observed in several photorefractive crystals including BaTiO₃, KNbO₃, Sr_1-xBa_x Nb₂O₆ (SBN), Ba_2-xSr_xK_1-yNa_yNb₅O₁₅ (KNSBN), and Bi₁₂TiO₂₀ (BTO). Phase conjugation reflectivity of up to 30% has been reported. In this work we report we believe for the first time self-pumped phase conjugation in Fe doped (K_xNa_1-x)_0.4(Sr_yBa_1-y,)_0.8Nb₂O₆ (KNSBN) crystals using the external ring geometry. The phase conjugation reflectivity has been measured as a function of the light wavelength, light intensity, and the angle between the incident beam and the crystal c-axis. Larger phase conjugation reflectivities are observed for higher light intensity and shorter light wavelength. Phase conjugation reflectivity of up to 37% has been measured. Phase conjugated images of high quality are observed. The rise time and decay time of the phase conjugate image are measured. Fast rise (decay) followed by a much slower rise (decay) is observed. These two time constants indicated that two photorefractive gratings are involved in the phase conjugation process.

© 1989 Optical Society of America