Interference filters for the millimeter and submillimeter spectral region

The properties of a Fabry-Perot interferometer (FPI) with mirrors in the form of metal gratings are discussed. For obtaining filters for the submillimeter and millimeter spectral region we suggest the use of an interferometer with crossed gratings, each grating being enclosed between dielectric plates. Our studies have shown that the half-width of the transmission band of such a filter amounts to 0.6 mm at =8.4 mm, the transmissivity being 77%.In conclusion, the authors wish to express their gratitude to M. A. Leontovich for valuable discussions and to V. D. Rusanov and V. M. Plekhov for their collaboration in the work.