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

Alexander Mamrashev,Valery Antsygin,Nazar Nikolaev,Fedor Minakov

doi:10.3390/photonics8060213

Alexander Mamrashev, Valery Antsygin + Show 2 more

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https://doi.org/10.3390/photonics8060213

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Journal: Photonics	Publication Date: Jun 10, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: Institute of Automation and Electrometry

Abstract

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 (THz-TDS). 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.

Highlights

Terahertz time-domain spectroscopy (THz-TDS) is a mature technique that allows for measuring the optical, dielectric, and conductivity properties of materials in the terahertz spectral range
It occurs because a polarizer is used to rotate the polarization of generated terahertz radiation by an angle of 45◦ and the electro-optic detection sensitivity is lower for terahertz radiation that is polarized at 45◦
We analyzed the sensitivity of electro-optic detection systems of terahertz time-domain spectrometers based on (110)-cut and (111)-cut zincblende crystals and its dependence on the polarization of terahertz and probe laser radiation

Summary

Introduction

Terahertz time-domain spectroscopy (THz-TDS) is a mature technique that allows for measuring the optical, dielectric, and conductivity properties of materials in the terahertz spectral range It is commercially available and has a wide range of applications spanning various domains of science, technology, and art. The inherent dependence of electro-optic detection sensitivity on the polarization of terahertz and probe laser radiation can be employed [12,13] In this case, a detector crystal [14,15,16], the probe pulse polarization [17], or the polarization of the generated terahertz radiation [18] is steadily rotated and the signal is measured using lock-in techniques at the rotation frequency or its harmonics. Setups with a steady rotation of polarizers at 5−15 Hz with lock-in measurements at twice the rotation frequency are suggested [20,21,22]

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