This chapter reviews different suggestions for applications of PRCs. Due to the high sensitivity, high diffraction efficiency, reversibility, and the ease of handling, these dynamic photosensitive media attracted the attention of researchers working in different areas of coherent optics. Early proposals on the use of photorefractive crystals and SLMs for holographic interferometry and 2D image processing are still interesting. Recently, a number of new ideas on PRC applications based on various phase-conjugate geometries have appeared, too.

http://iopscience.iop.org/article/10.1088/0034-4885/57/1/002/pdf

Applications of photorefractive crystals

We report the real-time direct interference-term measurement for a two-wave-mixing experiment in photorefractive crystals. Knowledge of the interference term may provide information concerning diffraction efficiency, interference pattern-to-recorded hologram phase shift, and optical activity and anisotropic diffraction properties of these materials. This method comprises phase modulation of one of the interfering beams and synchronous detection of the first and second harmonics in the resulting output irradiance modulation. Simultaneous detection of both harmonics enables the measurement to be made even in strongly perturbed conditions, since one harmonic is used for measuring and the other is used for operating an active stabilization system. Experimental results for Bi12TiO20 are reported.

Interference-term real-time measurement for self-stabilized two-wave mixing in photorefractive crystals.

We theoretically analyze a two‐wave mixing interaction in photorefractive Bi12SiO20 crystals in which the amplitude of the signal beam is time modulated at high frequency. Calculations of the photoinduced space‐charge field are derived for a sinusoidal modulation of the input signal. Due to the time‐integrating properties of the nonlinear crystal, the transmitted signal exhibits a differential gain when the modulating frequency is much greater than the inverse of the material response time. Application to coherent homodyne detection of wave fronts carrying spatial and temporal information is also presented.

Two‐wave mixing with time‐modulated signal in Bi12SiO20 theory and application to homodyne wave‐front detection

Nonstationary holographic recording for efficient amplification and phase conjugation

We report a new nearly degenerate two‐wave mixing interaction in photorefractive Bi12SiO20 crystals in which the signal beam is time modulated at high frequency. The beam coupling phenomena and the time integration properties of the crystal allow us to achieve a differential gain γdiff on the transmitted signal beam. The dependence of γdiff versus the duty cycle of the modulated signal is analyzed. Amplification and regeneration of periodic, or random sequences of information bits are experimentally demonstrated.

Amplification of high bandwidth signals through two‐wave mixing in photorefractive Bi12SiO20 crystals

During the erasure of a photorefractive grating in Bi12SiO20, the space-charge field moves at a constant velocity and its amplitude exponentially decays. The experiment confirms that the diffracted beam is frequency-shifted and the amount of frequency shift is equal to that required for optimum beam coupling in nearly degenerate two-wave mixing.

B. Loiseaux

Papers

Amplification of high bandwidth signals through two‐wave mixing in photorefractive Bi12SiO20 crystals

Moving grating during erasure in photorefractive Bi12SiO20 crystals