We provide a frequency-domain picture of the electro-optic (EO) detection of elliptically polarized terahertz radiation utilizing the crystal angle dependence of the EO effect using zinc blende crystal symmetry. In contrast to EO detection of a linearly polarized terahertz pulse, the measured EO signal would not be a replica of the terahertz pulse, even though the phase-matching condition is completely fulfilled. However, the rotation of the EO crystal reduces the complexity, and the ellipticity and the angle of rotation of each frequency component of the elliptically polarized terahertz pulse can be determined irrespective of what kind of zinc blende crystals are used for the EO detection. We experimentally show that the ellipticity and angle of rotation are reproducibly obtained by using three different crystals with different thicknesses and compositions. Direct detection of the elliptically polarized terahertz radiation enables us to precisely determine the optical axis and retardation of a quartz crystal using the Poincare sphere representation of the state of polarization. (C) 2014 Optical Society of America
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