Optical waveguide techniques for structural and chemical analysis in thin film and interfacial systems

This review considers some of the problems with which analytical chemists interested in thin-film and interfacial structures must deal. It is advocated that the types of classical spectroscopies which have served so well for so long in the solution regime are not particularly well suited to attacking these problems and that entirely new approaches are required. One such approach uses the generation of resonant optical waveguide modes in thin-film structures as the basis for spectroscopic excitation. The details of the waveguiding process are discussed and the properties important for spectroscopic experiments emphasized. The power of the technique for generating qualitative spectroscopic information is demonstrated by considering some specific Raman and resonance Raman experiments, and the implementation of an optical depth profiling capability is discussed. Finally, some recent four-wave mixing experiments are detailed to demonstrate both the breadth of capabilities and the vitality of research in the area. It should be noted that several fairly extensive efforts have not been covered. Notable among these is the use of resonant optical modes for thin-film absorption spectroscopy in which active research is ongoing (D. A. Stephens and P. W. Bohn, unpublished results).