Enhanced-Raman scattering from organic thin films in an attenuated total reflection geometry mediated by half-leaky guided modes

In an attempt to achieve enhanced Raman scattering without metallic thin fi lms, an attenuated total reflection (ATR) arrangement consisting of a prism , amorphous SiO2 gap layer, copper phthalocyanine (CuPc) thin film and fuse d quartz substrate was constructed. The ATR spectra exhibited sharp dips co rresponding to the excitation of electromagnetic normal modes of the multil ayer system. Under the excitation of thr modes, Raman scattering from the C uPc film was found to be enhanced by a factor of similar to 10(2) over the normal Raman scattering. Detailed analyses based on electromagnetic theorie s suggest that the presently observed Raman enhancement is caused by strong electromagnetic fields induced in the CuPc film upon excitation of half-le aky guided modes. The electromagnetic field associated with the HLGM is lea ky in the prism, a guided-wave type inside the gap layer and exponentially decays inside the substrate. (C) 1999 Elsevier Science S.A. All rights rese rved.