Propagation of Surface Polaritons at Optical Frequencies over Macroscopic Distances along Semi-Infinite Interfaces.

摘要

We have recently reported the observation of surface polariton propagation at metal-air interfaces over macroscopic distances (centimeters) at optical frequencies (10.6 micrometers). A prism coupling technique was used both to excite and detect the surface polaritons. The propagation length of the surface mode was found by measuring the intensity of the output coupled EM radiation with a pyroelectric detector as a function of the separation between the input and output prism couplers. Radelin thermographic phosphor paper was also used for the direct visual observation of both the surface and EM modes. We present here further experimental data on the generation, propagation, and detection of surface polaritons at various metal-air interfaces and a more detailed theoretical discussion of their nature. In the absence of surface roughness, the attenuation of surface modes at a metal-air interface arises from electronic relaxation in the metal. In the case of metal-dielectric interfaces, the attenuation arises from losses in the surface active (metal) and surface inactive medium. Information about the real and imaginary parts of the dielectric constant can be obtained by combining measurements of the dispersion relation. (Author)