Enhanced-Raman scattering from organic thin films mediated by half-leaky guided modes

ill order to achieve enhanced-Raman scattering without a metallic thin film s, an attenuated total reflection (ATR) arrangement consisting of a prism, an amorphous SiO2 gap layer, a copper phthalocyanine (CuPc) thill film and a fused quartz substrate was constructed. The ATR spectra exhibited sharp d ips corresponding to the excitation of half-leaky guided modes, which are l eaky in the prism, guided waves inside the SiO2 gap layer and exponentially decay inside the substrate. Under excitation of the modes, Raman scatterin g from the CuPc film was found to be enhanced by a factor of similar to 10( 2) over the normal Raman scattering. The present Raman enhancement can be w ell explained by strong electromagnetic fields induced in the CuPc film upo n excitation of the half-leaky guided modes. (C) 1999 Elsevier Science B.V. All rights reserved.