A series of FIR bandpass filters which consist of two resonant grids with resonant wavelengths lambda //m greater than 200 mu m were constructed. The dependence of the spectral characteristics of the filters on the separation between grids was studied experimentally in separation range of 0 to 80 mu m by means of the FIR Fourier transform spectrometer in the wavenumber region of 40 to 200 cm-**1 . It is found that the resonant wavelength and bandwidth of the filter vary with the separation between grids. The rejection in the stopband is greatly increased, and the maximum transmission coefficient in the passband is as high as 75%.
|Published - 1985
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