| Summary: | For the first time, we present the spectra of all three components of the refractive index and absorption coefficient of the KTiOAsO<sub>4</sub> (KTA) crystal measured by the means of terahertz time-domain spectroscopy in the range of 0.3–2.1 THz. The dispersion of the refractive index is approximated and presented in the form of the Sellmeier equation. We observe a large birefringence Δ<i>n<sub>Z-X</sub></i> » 0.76 and dichroism which is attributed to a strong absorption peak in the vicinity of ~1.23–1.25 THz for the <i>Z</i>-axis. However, the crystal can be considered as almost uniaxial due to a close value of <i>n<sub>X</sub></i> and <i>n<sub>Y</sub></i>as well as α<sub>X</sub> » α<sub>Y </sub>in the region below 0.5 THz. Moreover, KTA crystals can satisfy the phase-matching condition in principal <i>XZ</i>-plane for THz emission on difference frequency generation mechanism. Therefore, the crystal could be considered as an efficient candidate for terahertz wave generator under intense laser pump.
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