Multilayer Thickness Measurements below the Rayleigh Limit Using FMCW Millimeter and Terahertz Waves

Quarter-wavelength multilayer interference filter for terahertz waves

This work presents a multilayer interference filter, suitable for operation with terahertz waves (T-rays). An analysis of the effect of the number of layers on the spectral response is given, with full measurement data including time-resolved signals, transmittances, and phase spectra. The silicon–air structure with a submillimeter thickness shows a stop-band between 0.2 and 0.5 THz, and the at...

Engineering the properties of terahertz filters using multilayer aperture arrays.

We experimentally demonstrate the ability to create additional transmission resonances in a double-layer aperture array by varying the interlayer gap spacing. In the case of periodic aperture arrays, these additional resonances are sharply peaked, while for random aperture arrays the resonances are broad. Surprisingly, these additional resonances only occur when the interlayer gap spacing is gr...

Terahertz Imaging, Millimeter-wave Radar

The millimeter wave (MMW) band of frequencies extends from 30 GHz to 300 GHz, with some fuzziness on both ends of this spectrum. The terahertz (THz) band extends from about 200 GHz to about 30 THz, despite the fact that the lower frequencies in this range are not strictly 10 Hz or higher. These bands are also variously called submillimeter, far-infrared, and near-millimeter. In recent years, th...

Generation of ultra-narrow, stable and tunable millimeter- and terahertz- waves with very low phase noise.

The interference between two spectral lines of the frequency comb of a fiber femtosecond laser is used to generate millimeter-wave and terahertz tones. The two lines are selected by stimulated Brillouin scattering (SBS) amplification. All other modes are strongly rejected based on polarization discrimination, using the polarization-pulling effect that is associated with SBS. The inherent high s...

First Density Profile Measurements Using FMCW Reflectometry on JET