THz Waveplates

THz Waveplates

Polarimetry technique is very important for analyzing the THz radiations (divergence, spatial or frequency modes, and profiles). The key instrument in polarimetry is polarization modulator which identifies and measures polarized signal.

Plano-plano plates, made of birefringent material, are used for modifying polarization state of radiation. A waveplate works by shifting the phase between two perpendicular polarization components of the wave. The most common types of waveplates are a half-wave plate (λ/2 plate) and a quarter-wave plate (λ/4 plate). λ/2 plate gives phase delay π and λ/4 plate — π/2. A half-wave plate changes the polarization direction of linear polarized light. A quarter-wave plate changes linearly polarized light to circular and vice versa. Waveplate will not change the polarization of linearly polarized beam if the polarization direction is along one of waveplate axes.

Operating principle of half-wave and qurter-wave plates is shown below:

Half-wave plate



Quarter-wave plate

Tydex offers the THz waveplates for single operation wavelength: 

Common specification:

Segmented waveplate consisting of several specially oriented half-wave plates allows getting radiation with radial and azimuthal polarization from linearly polarized one. Operating principle of such waveplates is shown below.

Radial polarization can be changed to azimuthal one by rotating segmented waveplate at 45 degrees. Direction of radial polarization becomes the opposite one by rotating the waveplate at 90 degrees. Combination of segmented waveplate with positive lens gives radiation polarized along to its propagation direction.

Segmented waveplates are manufactured upon request.