Abstract-Terahertz time-domain polarimetry (THz-TDP) based on the spinning E-O sampling technique: determination of precision and calibration

Kuangyi Xu, Elyas Bayati, Kenichi Oguchi, Shinichi Watanabe, Dale P. Winebrenner, and M. Hassan Arbab

 Schematic of the THz Time-Domain Polarimetry (THz-TDP) system. The ZnTe detector is rotating at a constant frequency, ω. BS1-BS2: beam splitters; ND: a variable neutral density filter wheel; GT1-GT2: Glan-Thompson polarizers; QWP1-QWP2: quarter-wave plates; HWP: a half-wave plate; S: position of sample holder; PM1-PM2: off-axis parabolic mirrors; HR-Si: a high resistivity silicon wafer used to block the NIR pulses; L: a plano-convex lens; WP: a Wollaston prism. Inset: configuration of the electro-optic sampling. The polarization direction of the probe beam is set parallel to the x-axis in the laboratory frame. β is the orientation of the [-110] axis of the (110)-cut ZnTe crystal and γ is the polarization angle of the terahertz electric field vector with respect to the probe beam.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-9-13482

We have developed a terahertz time-domain polarimetry (THz-TDP) system by applying frequency modulation to electro-optic sampling detection in a nonlinear crystal. We characterized the precision of this system in determining the polarization angles to be 1.3° for fixed time delay, and 0.5°for complete time-domain waveform. Furthermore, we calculated the Jones matrix of the optical components used for beam propagation to calibrate the induced systematic error. The advantages of employing this calibration approach are demonstrated on a sapphire crystal investigated at different sample test positions in transmission configuration, and using high resistivity Si, AlN and quartz in reflection geometry. The new THz-TDP technique has the advantage of not using any external polarizers, and therefore is not constrained by their optical performance limitations, such as restricted bandwidths and frequency-dependent extinction ratio. Finally, the THz-TDP technique can be easily implemented on existing time-domain spectroscopy (TDS) systems.

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