The excitation of terahertz-range surface plasmons by frustrated total internal reflection through the substrate

A method of exciting surface plasmons in the terahertz range using the Kretschmann layout of the frustrated total internal reflection method is proposed and tested. The method involves making the illuminated part of the metallic layer transparent, with its thickness smoothly increasing in the direction in which the radiation propagates. This makes it possible to excite terahertz-range surface plasmons without the incident radiation simultaneously generating parasitic diffraction satellites of these plasmons. The SNR in terahertz surface spectroscopy and plasmon sensor devices is increased by using this method. Experiments to test the method have been carried out on gold, using the radiation of the Novosibirsk free-electron laser. (C) 2010 Optical Society of America.