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Neodymium-doped polyvinyl alcohol films were prepared and the optical properties of the films were investigated. By applying Judd-Ofelt theory, the X parameters were obtained from the absorption spectrum. Various radiative parameters like transition probability for each level (A J ), total transition probability (A T ), branching ratio (b R ), radiative lifetime (s rad ), and absorption cross-section (r A ) were calculated. The theoretically obtained branching ratio and integrated absorption cross-section are found to be greater for the transition 4 F 3/2 ! 4 I 11/2 . From the emission spectrum peaked at 1064-nm stimulated emission cross-section (r E ), the line width (Dk eff ) is calculated to be 6.21 Â 10 À21 cm 2 and 41 nm, respectively. Further the variation of the optical gain with the length of the film was studied and the slope efficiency (g ¼ 8.5%) was determined from laser measurements. These results clearly support the potentiality of the Nd 3þ : polyvinyl alcohol films in realizing optical amplification and stimulated emission.

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The propagation of laser beam in a flow aligned nematic liquid crystal (NLC) and its interaction with liquid are illustrated in this letter. The effect of polarization and scattering on the transmitted power through the NLC under external perturbation flow is demonstrated here. It is found that the flow rate has a significant role in the modulation of refractive index of the medium leading to scattering and change in polarization. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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