Millimeter wave complex refractive index and dielectric permittivity measurements of crystalline sapphire between 4 and 300 k

Mohammed Nurul Afsar

doi:10.1117/12.2297938

1 October 1991 Millimeter wave complex refractive index and dielectric permittivity measurements of crystalline sapphire between 4 and 300 k

Mohammed Nurul Afsar

Author Affiliations +

Proceedings Volume 1576, 16th International Conference on Infrared and Millimeter Waves; 157669 (1991) https://doi.org/10.1117/12.2297938
Event: 16th International Conference on Infrared and Millimeter Waves, 1991, Lausanne, Switzerland

Abstract

Broadband complex refractive index and complex dielectric permittivity spectra are measured at several cryogenic temperatures for crystalline sapphire over the frequency range 100 - 450 GHz. The dispersive Fourier transform spectroscopy was employed together with a special interferometer for low temperature operation. At 180 GHz the absorption coefficient value only reduced to about one half for both 76 K and 5.8 K compared to its value at 300 K. At 280 GHz the absorption value at 76 K remains to about one half of its value at 300 K but drops to about 20 percent at 5.8 K. The earlier reported temperature squared dependence (decrease) in the absorption coefficient value is totally absent in our data at frequencies below 300 GHz. The average value of the real part of the dielectric permittivity decreases with decreasing temperature.

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Mohammed Nurul Afsar "Millimeter wave complex refractive index and dielectric permittivity measurements of crystalline sapphire between 4 and 300 k", Proc. SPIE 1576, 16th International Conference on Infrared and Millimeter Waves, 157669 (1 October 1991); https://doi.org/10.1117/12.2297938

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