Planar Michelson Interferometer Using Terahertz Surface Plasmons

Abstract

Abstract: The optical scheme and technical characteristics of terahertz planar Michelson interferometer based on surface plasmons are presented. A technique for determination of the complex index of refraction of surface plasmons (Formula presented.) from interferograms is described. The paper presents the results of test measurements on flat surfaces with gold sputtering coated by ZnS layers 0 to 3 μm thick with application of the high-power coherent radiation from the Novosibirsk free electron laser at the wavelength λ0 = 141 μm. From the measurement results, the value of the effective permittivity of the sputtered gold surface was found, which turned out to be an order of magnitude lower than that of crystalline gold. Analysis of the energy losses in the plasmonic interferometer made it possible to estimate its dynamic range (106–108 in terms of radiation power) required for measurements on samples with different (Formula presented.). Ways to increase the signal-to-noise ratio via optimization of the elements of the optical scheme and detector have also been proposed.