Reflection-grating based photorefractive phase conjugator and ring resonator

Abstract

Photorefractive materials, such as BaTiO3, KNbO3, SBN, etc. are known to exhibit high nonlinearity at low optical intensities. High fidelity optical phase conjugation and various optical resonators have been demonstrated in a variety of photorefractive crystals.1 Most of these phase conjugators and oscillators are based on the transmission type of gratings, which are relatively slow depending on the kind of crystal and optical intensity used. Reflection gratings, on the other hand, have the potential to respond faster than the transmission grating because the photo-induced charges move much shorter distances in the photorefractive materials. Recently, a self-pumped phase conjugator based on the reflection gratings in KNbO3 has been demonstrated to achieve a millisecond response time.2 In this paper, we present a systematic study on the reflection-grating based two beam coupling, self-pumped phase conjugation and, for the first time, unidirectional ring oscillations in the Fe-KNbO3 crystal. Fast response time has been observed experimentally in both two beam coupling and unidirectional ring oscillation. Good phase conjugate fidelity has been achieved from the self-pumped phase conjugators.