Diffraction characteristics of general dielectric planar (slab) gratings and surface-relief (corrugated) gratings are reviewed. Applications to laser-beam deflection, guidance, modulation, coupling, filtering, wavefront reconstruction, and distributed feedback in the fields of acoustooptics, integrated optics, holography, and spectral analysis are discussed. An exact formulation of the grating diffraction problem without approximations (rigorous coupled-wave theory developed by the authors) is presented. The method of solution is in terms of state variables and this is presented in detail. Then, using a series of fundamental assumptions, this rigorous theory is shown to reduce to the various existing approximate theories in the appropriate limits. The effects of these fundamental assumptions in the approximate theories are quantified and discussed.

Analysis and applications of optical diffraction by gratings

Holography, coherent light amplification and optical phase conjugation with photorefractive materials

The development of a theory of four-wave mixing in photo-refractive crystals is described. This theory is solved in the undepleted pumps approximation with linear absorption and without using the undepleted pumps approximation for negligible absorption. Both the transmission and reflection gratings are treated individually. The results are used to analyze several photorefractive phase conjugate mirrors, yielding reflectivities and thresholds. The use of photorefractive crystals as optical distortion correction elements and experimental demonstrations of several of the passive phase conjugate mirrors are described.

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Theory and applications of four-wave mixing in photorefractive media

The real-time information processing and manipulation of electromagnetic waves using nonlinear Qptical techniques has resulted in a myriad of new applications in diverse fields such as quantum electronics, image processing, optical computing, adaptive optics, and nonlinear spectroscopy. In this paper, we review and explore the field, provide a historical perspective, analyze several of the nonlinear interactions useful for the generation of phase-conjugate replicas, and conclude with a brief survey of potential applications and suitable nonlinear media.

Nonlinear Optical Phase Conjugation

The polarization properties of diffraction from volume phase gratings in photorefractive sillenite crystals such as bismuth silicon oxide (Bi12SiO20), bismuth germanium oxide (Bi12GeO20), and bismuth titanium oxide (Bi12TiO20) are strongly modified by the presence of concomitant natural optical activity and electric-field-induced linear birefringence. A set of coupled-wave equations that characterize the Bragg regime has been derived for the 〈110〉 and the 〈001〉 crystallographic orientations typically employed in volume holographic storage and multiwave-mixing applications. The predicted anisotropic behavior of the grating diffraction is experimentally confirmed, and a significant efficiency improvement is shown to occur for proper choice of the operating mode and the probe beam polarization in a given configuration.

Polarization properties of photorefractive diffraction in electrooptic and optically active sillenite crystals (Bragg regime)

Photoconductive eiectrooptic crystals such as Bi12SiO20 (BSO) are attractive materials for read-write volume phase hologram recording. As reported in Ref. 1 the recording and erasure energy (S 1 ) with an external applied field have been found to be equivalent to that of high resolution photographic plates (S ≃ 130 μJ/cm η = 1%; λ = 488 nm). In addition, excellent quality reconstructed images and no fatigue effects to reversibility were reported. Physical mechanisms for ho­ logram recording and erasure are drift and trapping of photoelectrons under fringe illumination with a transverse eiec­ trooptic configuration. This gives rise to a space-charge field which modulates the refractive index via the linear eiec­ trooptic effect. Hologram erasure is achieved by space-charge relaxation under uniform illumination with the reference beam. A typical experimental recording-erasure cycle with a 6-kV applied field is given in Fig. 1. More precise analyses of the space-charge build-up and relaxation in photosensitive

J. P. Herriau

Papers

Time average holographic interferometry with photoconductive electrooptic bi12sio20 crystals

Time average holographic interferometry with photoconductive electrooptic Bi(12)SiO(20) crystals.