Volume holograms in photochromic materials.

Theoretical expressions are derived describing the process of writing volume (or thick) hologram gratings in photochromic materials. The theory includes the effects of the saturation of the material response, scattering of the writing beams by the partially written hologram, and the refractive index changes that accompany the photoinduced absorption changes. Results of representative numerical calculations are presented and interpreted in terms of simpler models and approximations. Use of the results is illustrated by the calculation of the holographic characteristics of an actual material. The results are also related to model photochromic systems to estimate the range of achievable holographic characteristics and to obtain an approximate procedure to estimate the absorption spectra of materials that would give specified holographic characteristics.