Terahertz polarization conversion with quartz waveplate sets.

We present the results of calculation and experimental testing of an achromatic polarization converter and a composite terahertz waveplate (WP), which are represented by sets of plane-parallel birefringent plates with in-plane birefringence axis. The calculations took into account the effect of interference, which was especially prominent when plates were separated by an air gap. The possibility of development of a spectrum analyzer design based on a set of WPs is also discussed.