Polarization sensitive terahertz time-domain spectroscopy for birefringent materials

Recent Advances in Birefringence Studies at THz Frequencies

“…The orientation of the optical axis of a LiNbO 3 crystal was determined for a 45°orientation of the THz emitter, where the ratio of E y /E x evaluated at a single frequency exhibited maxima when the THz polarization coincided with the ordinary (o) or extraordinary (e) axis of the rotating sample. Also in [83], two orthogonal polarization components were detected, in that case by rotating a (110) ZnTe detection crystal by 90°. Maxima in the one and correspondingly minima in the other polarization component of the peak spectral amplitude as a function of the azimuthal angle were found for a quartz crystal sample when the e-or o-axis was aligned along the detection axes.…”

“…In [81], a wire-grid polarizer was rotated after the sample to selectively measure the horizontal and vertical THz electric field components, respectively, not giving any details about the detection principle. Alternatively, the polarization sensitivity of the EO effect was directly exploited: by an appropriate rotation of the crystallographic axes of an EO (110) ZnTe detection crystal, only the desired polarization component produced a signal [82,83]. A rotation of the detector can also be implemented with PCAs, where the use of fibercoupled antennas facilitates this procedure [84].…”

Terahertz polarization imaging with birefringent materials

“…Meanwhile, the polarization property variation, which carries important information about the anisotropy, nonhomogeneity or intrinsic structural changes of the target material, has also been widely studied as features in THz inspection modalities [9][10][11]. Some techniques have been developed to enable polarization characterization in THz imaging systems, either by measuring the two orthogonal components of the output THz signal or varying the polarization of the incident THz beam [10][11][12].…”

“…Recently, some THz birefringent materials were studied using THz time domain spectroscopy (TDS) [9][10][11][12]. The polarization sensitive properties of THz birefringent materials provide the possibility of a new approach toward THz polarization imaging.…”

“…In electro-optical sampling THz detection configuration, when the (001) axis of the (110)-oriented ZnTe is fixed at the vertical direction and the polarization of the probe beam is horizontal, one can measure the horizontal component of the incoming THz electric field amplitude [12]. When a predominantly horizontally polarized THz waveê in t ð Þ is normally incident on a birefringent crystal with its optical axis oriented at 45°, two separate pulse maxima can be detected if the crystal has a difference in the optical path lengths for ordinary (o) and extraordinary (e) rays larger than the THz pulse width.…”