Cadmium sulfide semiconductor nanoparticles along with terbium ions were incorporated in silica xerogels through sol-gel route. The optical absorption and emission spectra confirmed the formation of CdS nanoparticles along with terbium ions in the silica gel. The optical bandgap and size of the CdS nanoparticle were calculated from the absorption spectrum. The TEM measurement was also used to evaluate the average size of the CdS nanoparticles. The fluorescence spectra reveal that the intensity of characteristic emission of terbium ions increases considerably in the presence of CdS nanoparticles even in the gel stage itself and this avoids the need of heating gels at high temperatures. The branching ratios were calculated from the emission spectra using the standard procedure.

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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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