ABSTRACT
The quasi-optical modulation of linear polarization at millimeter and sub-millimeter wavelengths can be achieved by using rotating half-wave plates (HWPs) in front of polarization-sensitive detectors. Large operational bandwidths are required when the same device is meant to work simultaneously across different frequency bands. Previous realizations of half-wave plates, ranging from birefringent multi-plates to mesh-based devices, have achieved bandwidths of the order of 100%. Here we present the design and experimental characterization of a reflective HWP able to work across bandwidths of the order of 150%. The working principle of the novel device is completely different from any previous realization, and it is based on the different phase-shift experienced by two orthogonal polarizations reflecting, respectively, off an electric conductor and an artificial magnetic conductor.
ABSTRACT
Characterization of the topography of materials by interferometry in the visible or near-IR wavelength regime becomes difficult or impossible if the surface is rough on the length scale of a tenth of the wavelength and more. In this case, THz radiation can provide an interesting alternative. We demonstrate heterodyne profilometry at 600 GHz as a method for the accurate determination of surface topography with an achievable expanded standard uncertainty of 0.5 mum.
