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Photochem Photobiol Sci. 2013 Oct;12(10):1780-6. doi: 10.1039/c3pp50065a.

Azo doped polymer thin films for active and passive optical power limiting applications.

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Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prashanti Nilayam, Andhra Pradesh 515134, India.


Two novel optical power limiters, 2-[ethyl-(4-phenylazo-phenyl)-amino]-ethanol (E4PA) and 2-[ethyl-(4-trifluoromethyl-phenylazo-phenyl)-amino]-ethanol (E4TPA) were synthesized using a diazotization reaction. The purified azo material was made into thin films in a poly(methyl methacrylate) matrix using a gravity settling technique. The electronic nonlinearities of these films were investigated using an open aperture Z-scan technique in the fs excitation regime, resulting in nonlinear absorption due to a two-photon absorption (2PA) process. The 2PA coefficient for these films is of the order 10(-12) m W(-1) and the limiting threshold values are 1.1 J cm(-2) each. A non-degenerate pump probe set-up was employed with CW lasers to study the nonlinear behaviour arising from photo-induced anisotropy and excited-state absorption. The present study shows that these azo thin films are potential candidates for active and passive optical power limiting applications.


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