Broadband wave plates in the terahertz region
We have demonstrated the fabrication of broadband half wave (l/2) and quarter wave (l/4) plates in the terahertz (THz) frequency region. The l/2-plate consisting of a rooftop-mirror and a plane mirror. The operation principle of l/4 wave plate is based on the phase shift difference in the total-reflection for s and p polarization at the bottom of a dove-prism made of high resistivity silicon. Both of the wave plates have clear apertures of 15 mm, and are thus made possible to install in commercially available optics, such as using lens tubes. We have carried out evaluation experiments by using a THz time-domain spectroscopy (THz-TDS) system, and found that they have satisfactory performance as broadband wave-plates in the terahertz region.