Optical constants of some commercial microwave materials between 90 and 1200 GHz

The optical constants of three commercial microwave materials have been determined between 90 and 1200 GHz at 290 K by the techniques of dispersive Fourier-transform spectroscopy. The materials studied were a cast microwave absorber known as Ferroflow, a machinable glass ceramic known as Macor and a substrate material for planar microwave circuitry known as Epsilam-10. The former two of these have been shown to be potentially suitable for use as thermal sources for the absolute calibration of radiometric instrumentation. The glass ceramic has also been shown to have a broad absorption band centred on 9 cm¿¿1 that is obscured in the absorption spectrum by its rapid increase to high wave number, but that is clearly seen in the refraction spectrum.