A NEW CLASS OF FAR INFRARED FILTERS.

Author Institution: Department of Physics, The Ohio State UniversityThe structure of metallic mesh may be considered as to be generated by multiple reflections of a square iris at the walls of a square waveguide. Starting with other ``unit cells'' for the two-dimensional grid than the iris, more general types of metallic mesh have been produced and their optical properties measured. These structures are the free space equivalents of the corresponding waveguide obstacles. Their filter characteristics can be considerably enhanced by stacking several filters, thus forming the equivalent of multi-cavity waveguide filters. Examples of lowpass, high-pass, and bandpass filters are reported. They show high passband transmission and steep transition to stopband. They are useful for spectroscopic work in the 100-1000 micron wavelength region where good restrahlen filters are lacking