Complex Dielectric Permittivity Measurements of Glasses at Millimeter Waves and Terahertz Frequencies

Accurate complex dielectric permittivity of several new glass specimens are reported for the first time using free-space dielectric measurement techniques in the millimeter-wave and terahertz region. Quasi-optical W-band (70-118 GHz) spectrometer with a backward-wave oscillator as a high power tunable source of coherent radiation and dispersive Fourier transform spectrometer are outlined. Results indicate that the quasi-optical spectrometer is a versatile system to produce broad band data for medium and highly absorbing materials with a large range of insertion loss at millimeter wave frequencies. However, above 120 GHz dispersive transform spectrometer is more preferable to provide high resolution continuous spectra of dielectric permittivity up to 800 GHz. Complex dielectric permittivity data for several high purity fused silica glass and sheet glasses are presented