Propagation Length of Surface Plasmon Polaritons Propagating along Air-Metal Interface

We have experimentally measured the propagation length L of surface plasmon polaritons propagating along an air-copper and an air-copper on a CaF 2 film interfaces by using a CO 2 laser of wavelength 10.6 µ m. It is found that the CaF 2 film produces a change in the dielectric constant of copper and leads to a decrease of L . It is also shown that L varies with the evaporation speed of the copper film. In order to know the effect of surface roughness on L in the visible region, where various SP experiments have been carried out, we have investigated a roughness effect on the SP propagating along an air-silver interface at wavelength of 0.6328 µ m.