Abstract-Terahertz Time-Domain Polarimetry for Principal Optical Axes of Anisotropic Crystals

 

Alexander Mamrashev, Fedor Minakov, Nazar Nikolaev, Valery Antsygin, 

https://www.mdpi.com/2304-6732/8/6/213/pdf

We propose a method for measuring the terahertz properties for two principal optical axes of anisotropic crystals without optical activity using terahertz time-domain spectroscopy (THzTDS). The method put forward in this paper utilizes the inherent polarization sensitivity of the THz-TDS electro-optic detection system. We demonstrate the practical application of the method by measuring the temperature dependence of the refractive index and the absorption coefficient of a lithium triborate crystal for three optical axes.

Abstract-Optical Properties of KTP Crystals and Their Potential for Terahertz Generation

Alexander Mamrashev, Nazar Nikolaev, Valery Antsygin, Yury Andreev,  Grigory Lanskii,  Arkady Meshalkin

http://www.mdpi.com/2073-4352/8/8/310

High nonlinearity, wide transparency range and optical quality allowed potassium titanyl phosphate (KTiOPO₄, KTP) crystals to be used in a wide range of nonlinear applications. The success of KTP usage in the visible and infrared (IR) ranges drives interest in applying it at longer wavelengths, that is, in the terahertz (THz) range. We use THz optical properties of KTP crystals measured by terahertz time-domain spectrometer (THz-TDS) and refractive index approximated in the form of Sellmeier equations to investigate KTP application possibilities for IR-to-THz and THz-to-THz wave conversion. As a result, phase matching for s − f → f and s − f → s types of difference frequency generation (DFG) of Ti:Sapphire laser (at the wavelengths of 0.65, 0.8 and 1.1 µm) is found possible, as well as second harmonic generation (SHG) of THz waves by f + s→f type of interaction in the XZ principle plane of the crystal. Terahertz wave generation by phase-matched parametric processes in KTP demonstrates evident advantages in comparison with that of widely used MgO-doped LiNbO₃ crystals