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Diffraction efficiency measurements of a He–Ne laser probe for three samples with spatial frequencies of 556, 1135, and . Left column [(a)–(c)] show temporal evolution of grating efficiency under Bragg condition during and after holographic exposure. The gray region in (a)–(c) indicates the exposure time interval, with the recording beams present. Right column [(d)–(f)] show the experimental results for the angular selectivity associated with each grating (dots) and the fits to Kogelnik’s theory (solid lines). Thickness of the grating , recording time, writing beam irradiance, Klein-Cook parameter , incident angle of the reading beam inside the material, and corresponding to efficiency are also shown.
Evolution of refractive index modulation in darkness. exposure of irradiance for three gratings with spatial frequencies of 556 (a), 1135 (b), and (c). Dots represent the experimental results and solid, dash, and dot lines are fits using expression (1) for the codirectional (I) and counterdiffusion (II and III), respectively. The parameters have been used as in Table I with the following signs: , , and for curves (I), (II), and (III), respectively.
Parameters used to fit experimental results displayed in Fig. 2 for codirectional diffusion.
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