Effects of cooling on surface em wave propagation and diffraction

The use of cooling to extend the range of wavelengths of surface electromagnetic waves (SEW) and the types of metals which will support SEWs is discussed, along with methods of improving the diffraction efficiency of metal gratings. Experimental results are cited to show that the propagation distances in lead and tin can be drastically increased if the metals are cooled to cryogenic temperatures. The cooling also permits the propagation of shorter wavelengths. Furthermore, cooling increases the Bragg diffraction efficiency by 100-300 percent, particularly when the distance between the gratings is equal to or greater than the mean free path of the SEW over an unrippled surface. If coupling occurs, then the propagation distance may also increase if the surface is heated.