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Observation of Unexpected Phase Deviation of Photo-Induced Dynamic Grating Formed in Azo-Carbazole Doped Polymer
Kazuhiro Tada, Kodai Fukuzawa, Toshio Yoshikawa, Toshiro Imai and Yutaka Kawabe

Some azobenzene derivatives have shown unusual asymmetric energy transfer in symmetric two-wave coupling alignment, although its mechanism is unknown. As a method to investigate the problem, we employed an ‘in situ’ technique to determine simultaneously the amplitude modulation of optical constants and its phase deviation induced under sinusoidal excitation light pattern. By applying an analytical approach based on volume grating theory, we succeeded to evaluate the temporal evolution of the constant modulation and phase deviation continuously in azo-carbazole dye NACzEtOH embedded in an inert polymer PMMA. The results revealed that the energy transfer was caused by a phase deviation of less than 90 degree at 633 nm, contrary to conventional photorefractive process. Comparison with experiments done at 532 nm suggests that the effect was caused by the motion of polymer matrix triggered by optical realignment of the azo-carbazole dye.

Keywords: photorefractive polymer, photo-induced orientation, azo dye, nonlinear optics, photochromism, photoisomerization

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