From partial to complete optical erasure of azobenzene–polymer gratings: effect of molecular weight

We demonstrate complete all-optical erasure of high-modulation-depth azopolymer surface patterns at ambient conditions. Applying selective optical erasure and rewriting can be translated into complex surface patterns with spatially varying grating vector directions.

Mixed phase and absorption thin gratings diffraction

The coupled wave theory of Raman and Nath diffraction is extended to the case of thin anisotropic holographic media with grating vector parallel to the medium boundaries. Solutions for the wave amplitudes, diffraction efficiencies, and angular mismatch sensitivities are given in transmission geometries for the case of mixed dielectric and absorption modulations. For an apparent distinction, the results are given only for dielectric modulation. The main difference of the new results, with respect to the expressions valid for isotropic media, arises due to the walk-off between the wave-front and energy propagation directions. The difference is particularly important in materials with large birefringence, such as organic crystals, ordered polymers, and liquid crystalline cells.