LINEAR AND NONLINEAR SPECTROSCOPY OF SURFACE ELECTROMAGNETIC-WAVES WITH A FREE-ELECTRON LASER

We present a set of problems that can be solved by using a novel highl y sensitive method of investigation of surface layers - spectroscopy o f surface electromagnetic waves. The field of application of this meth od was considerably extended with the use of a high-intensity FELIX fr ee-electron laser, which can be tuned within a broad spectral range. W e investigated CaF2 and LiNbO3 crystals in the far-IR range and studie d spectra of a selectively absorbing silicon-oxide-silver film in the spectral range of 900-1440 cm(-1). Nonlinear phenomena were observed o n crystal surfaces, including second-harmonic excitation on crystallin e quartz involving counterpropagating surface electromagnetic waves an d the generation of periodic surface structures on a LiNbO3 crystal.