Analysis of Wire-Grid Polarisers in Terahertz Spectral Range

Polarisers are important components in many optical applications working with polarised radiation, therefore it is need to know their behaviour at specified spectral range. Interest in terahertz (THz) radiation and its application in science, where we need polarisers was our motivation for study of commonly used polarisers this spectral range. In our paper we present THz measurement of free standing wire-grid (5 mu m tungsten wire, 12.5 mu m period) and polyethylene foil wire-grid (0.5 mu m metallic stripes, 1.2 mu m period) polariser. Measurements were performed by terahertz time domain spectroscopy in the range from 60 GHz to 3 THz (2-100 cm(-1)) at different rotation of azimuth angle. For quality evaluation was from measured data calculated extinction ratio and phase shift. Both polarisers were compared and their suitability for THz application is discussed. Results show better properties of free standing wire-grid polariser in the range up to 60 cm(-1) while properties of polyethylene polariser are better at higher wavenumbers. Polarisers are described in the frame of Jones matrix calculus.