Terahertz Birefringence and Dichroism of KTA Crystal

• Main Authors: Jingguo Huang, Yang Li, Yanqing Gao, Zhiming Huang, Nazar Nikolaev, Alexander Mamrashev, Grigory Lanskii, Yury Andreev
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Crystals
• Subjects: KTA; nonlinear crystal; terahertz time-domain spectra; optical properties; phase-matching condition
• Online Access: https://www.mdpi.com/2073-4352/10/9/730

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 Δ<i>n_Z-X</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_X</i> and <i>n_Y</i>as well as α_X » α_Yin 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.