High-speed photorefractive phase conjugator with large dynamic range and wide field of view

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Photorefractive materials have been used for demonstrating optical phase conjugation in a wide variety of configurations.1 A self-pumped photorefractive phase conjugator using internal reflection at the crystal faces (the CAT conjugator)2 has exhibited high fidelity. In this paper we describe a simple technique that uses the CAT conjugator to achieve optical phase conjugation with high speed (a few milliseconds to a fraction of a second), wide dynamic range of probe-beam intensities (less than a microwatt to tens of milliwatts), wide field of view (larger than ±50°), and a nearly uniform phase-conjugate reflectivity of approximately 15% throughout the entire range of intensities and angles. The "blackbox" consists of a CAT conjugator with a stabilized self-pumping beam and its phase-conjugate (of uniform or Gaussian intensity profile) of tens of milliwatts or higher. When a probe beam (from the same laser as the pumped beam) is properly injected into this black box, a phase-conjugate replica of the probe beam with the properties described above is generated by means of photorefractive four-wave mixing. Characterizations of this technique using a barium titanate crystal and potential applications for real-time image processing will be discussed.