Terahertz birefringence and dichroism of kta crystal

Abstract

For the first time, we present the spectra of all three components of the refractive index and absorption coefficient of the KTiOAsO4 (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 ΔnZ-X ≈ 0.76 and dichroism which is attributed to a strong absorption peak in the vicinity of ~1.23–1.25 THz for the Z-axis. However, the crystal can be considered as almost uniaxial due to a close value of nX and nY as well as αX ≈ αY in the region below 0.5 THz. Moreover, KTA crystals can satisfy the phase-matching condition in principal XZ-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.