Investigation of Dielectric Deep-Groove-Gratings as a Quarter Waveplate in the Terahertz Range

the diffractive optical elements based on planar high-resistivity silicon gratings are proposed to perform as a quarter waveplate as well as a half waveplate component in the selected band of THz frequencies. As proof of principle quarter waveplates we developed the Si-based quarter waveplate for 0.4 THz frequency demonstrating an operational bandwidth of up to 200 GHz. The finite difference time domain simulations were found in good agreement with THz time domain spectroscopy, frequency domain spectroscopy as well as vector network analyzer experiments measuring transmission amplitude and phase spectra in the range of 0.1-1.0 THz.