Optimization of prism coupling efficiency for surface electromagnetic wave excitation in the infrared

The ir SEW coupling efficiency of a BaF(2) prism has been determined for various gap heights and internal angle configurations, utilizing the two prism coupling technique and a CO(2) laser. Samples consisted of W foil and Ni, Pt, and Cu films deposited on glass substrates by electron beam deposition and vacuum evaporation. Optimum prism coupling gap heights were found to occur for each metal. It was determined that selection of the proper internal prism angle increases coupling efficiency by a factor of 3 over the coupling efficiency of the right angle prism.