Grid polarizers for infrared fourier spectrometers

Infrared grid polarizers consisting of copper lines with a 3.6 μm grid constant on a 4 μm thick mylar polyester substrate have been prepared by the techniques of photolithography and sputter-etching. Their polarization properties have been measured and found to be suitable for use at infrared frequencies below 700cm⁻¹. The polarizers have been used to extend the useful frequency range of a Martin-Puplett polarizing interferometer designed for Fourier transform spectroscopy. The efficiency of the interferometer has been measured over a frequency range from 50 to 700cm⁻¹ and compared to that of a conventional Michelson interferometer. The results are shown to be consistent with the measured properties of the polarizers. Methods are suggested for improving the efficiency of a Martin-Puplett interferometer which employs these polarizers.