Dielectric characterization of glasses at millimeter wavelength and terahertz frequencies

Abstract

Dielectric characterization of glasses and amorphous materials has been done with two terahertz time-domain spectroscopies at millimeter wavelength and terahertz frequencies. A quasi-optical free-space spectrometer is equipped with a backward-wave oscillator as a high power tunable source of coherent radiation and utilized in this research. The measurement technique is based on the transverse magneto-optical effect to enable the determination of the real and imaginary parts of complex dielectric permittivity of various glass specimens from 70 to 120 GHz. Above 120 GHz dispersive Fourier transform spectrometer is more effective to provide high resolution continuous spectra of dielectric permittivity up to 800 GHz. The real part of permittivity can be reproduced to 1 part in 100,000. The complex dielectric spectra of high purity fused silica glasses clearly show the existence of boson peaks at terahertz frequencies.