Complex Dielectric Measurements of Materials at Q- Band, V- Band and W- Band Frequencies with High Power Sources

In this paper we present a systematic study of complex dielectric permittivity of various semiconductor and dielectric materials, including highly absorbing substances, in Q-, V- and W-band frequencies. The measurements have been done using broadband quasi-optical millimeter wave spectrometer with a backward-wave oscillator (BWO) as a non-destructive high power tunable source of coherent radiation. Values of real and imaginary parts of dielectric permittivity of materials are calculated from the transmittance spectra. Refractive index data, obtained using both unbalanced waveguide bridge technique and free space measurements have been compared with previously published results. Millimeter wave and terahertz imaging and spectroscopy with high power BWO tubes as sources of coherent radiation for security applications have been briefly discussed