Yasuaki ITAKURA¹, Akihiro TOMIOKA^1,2,*, Sinji KINOSITA¹ and Tooru MOTOKUBOTA¹

¹Graduate School of Engineering, Osaka Electro-Communication University, 18-8 Hatucho, Neyagawa, Osaka 572-8530, Japan
²Academic Frontier Promotion Center, Osaka Electro-Communication University, 18-8 Hatucho, Neyagawa, Osaka 572-8530, Japan

(Received November 15, 2005; Accepted March 28, 2006)

We prepared transparent polymer films doped with π-conjugated organic dyes around a multimode silica fiber and observed very narrow fluorescence peaks as compared with the fluorescence in solution. The peak position showed no dependence on the excitation wavelength, indicating that it could not be explained by a whispering gallery mode. The peaks can be explained by amplified spontaneous emissions (ASEs) because the intensity depended linearly on the excitation intensity with a threshold. When the excitation laser was directly coupled to the fiber core, we observed ASE peaks of the optical fiber itself. These fiber ASE peaks shifted to longer wavelength when we varied the excitation to shorter wavelength, which clearly ruled out the possibility of silicate Raman scattering as the origin.

Key words: pi conjugated dye, dye doped, polymer film, photoluminescence

^*Corresponding author. E-mail address: tomioka@isc.osakac.ac.jp