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

The diffusion equation is solved in the low-order harmonic approximation, in order to describe the grating formation process in dry photopolymer materials. We describe how the ratio between diffusion and polymerization rates controls the process of grating formation. Nonlinearity and reciprocity failure are predicted. Experimental results are also shown which are in qualitative agreement with the theory.

Diffusion Model of Hologram Formation in Dry Photopolymer Materials

Thin and thick gratings: terminology clarification

Coupled wave description of the diffraction by zone plates with high aspect ratios

Volume phase holograms are formed by a standard process in commercially available photographic emulsion. The material is characterized before recording, and initial experimental results are presented for reconstruction under index-matched conditions. An initial comparison is made using two-wave coupled-wave theory and a technique of curve fitting with experimental measurements of transmission and diffraction efficiency. The model works well close to the Bragg condition, but several differences are noted between theory and experiment away from the Bragg condition. An anomalous absorptive effect is noted in transmission. An improved model is then formulated, again using coupled-wave theory, and capable of analytic solution, taking into account phase and absorption modulation, a second harmonic in the grating profile and the appearance of some higher diffraction orders. Using this model, all the initial experimental results are satisfactorily explained, and the effect of spurious gratings in the hologram response is noted. The model is then used with an extensive set of experimental results to deduce the major characteristics of the material, including saturation of the modulation with exposure. The formulation of a mixed grating and possible dispersion of the modulation are also investigated. Suggestions are made for the design of more complicated components using this material and for material improvement.

Planar volume phase holograms formed in bleached photographic emulsions.

The appearance of higher order diffracted modes is investigated for thick one-dimensional phase gratings. The criteria, determining the significance of the higher modes, are discussed and their validity illustrated by means of computer calculations.

D. J. Cooke

Papers

Higher Order Modes in Thick Phase Gratings

A two-dimensional theory of higher order modes in volume phase holograms