Optical Constants of Far Infrared Materials I: Analysis of Channeled Spectra and Application to Mylar

A method is presented for analyzing channeled spectra to determine optical constants, using fourier spectroscopy. The use of fourier spectroscopy is integral to the method, for a single signature of the channeled spectrum in the interferogram may be used to yield both real and imaginary parts of the refractive index. The method employed for handling the data permits use of the position of zero crossings to calculate the real refractive index rather than maxima and minima which cannot be located with the same precision. Determination of the order number of the zero crossings is discussed, as is the correction for the convergence of the illumination. Results are given for Mylar, a birefringent material, in the 50-250 cm(-1) region.