We have developed anisotropically etched low-loss artificial dielectric birefringent quarter-wave plates (QWPs) for use at 1.5 and 2.8 THz. The grating period for both QWPs is 20 ¿m. We etched 46- and 30- ¿m-deep gratings to obtain a ¿/2 phase retardance between transverse-magnetic and transverse-electric polarization propagating through the QWPs at 1.5 and 2.8 THz, respectively. A SU8 antireflection coating is used to further improve the transmission coefficient by up to 21%. The measured results from Fourier transform infrared spectroscopy show a good agreement with designed specifications.
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Saha et al. (2009) studied this question.
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