Abstract

We present and experimentally demonstrate a new method for enhancing the signal-to-background ratio of two-wave mixing in photorefractive crystals. The method uses a mutually incoherent third beam to suppress the fanning in a dark ring-shaped region in which the amplified signal is located. A 20-fold improvement of the signal-to-background ratio is measured in BaTiO₃ at λ = 514 nm. The extension of this principle to wide-field-of-view heterodyne detection is discussed.

© 1994 Optical Society of America

Low-noise photorefractive amplification and detection of very weak signal beams

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