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RESEARCH PRODUCT

<title>Angular selectivity of thin gratings</title>

subject

description

The angular selectivity of thin gratings is studied both experimentally and theoretically. The concepts of thick and thin gratings are analyzed. Thin holographic gratings recorded in a-As-S-Se films have exhibited pronounced and oscillatory diffraction efficiency angular dependences. These results are explained by the obliquity factor in Fresnel-Kirchhof diffraction integral and by finite beam and grating sizes. It is also shown that oscillatory diffraction efficiency angular dependences, most probably, arise due to the interference of diffracted waves of different orders because dephasing can be significant for small grating strengths and large enough readout angles. Fabry-Perot resonator effect can contribute as well. Thick gratings in a-As2S3 and a-As-S-Se films are also studied for comparison. The conclusion is made that normally all gratings possess angular selectivity and existing criterions underestimate the angular selectivity of thin gratings because they neglect factors other than dephasing.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.