Terahertz generation by optical rectification in uniaxial birefringent crystals

TL;DR

This paper investigates how birefringence in uniaxial crystals affects terahertz generation via optical rectification, revealing that crystal cut orientation significantly influences efficiency and angular emission patterns.

Contribution

It provides a detailed analysis of terahertz emission in birefringent uniaxial crystals, extending understanding beyond cubic crystals and predicting more efficient crystal cuts.

Findings

Birefringence causes polarization evolution, altering angular dependence of THz emission.

{114}-cut chalcopyrite crystals show higher conversion efficiency.

Angular emission patterns differ markedly from cubic crystal cases.

Abstract

The angular dependence of terahertz (THz) emission from birefringent crystals can differ significantly from that of cubic crystals. Here we consider optical rectification in uniaxial birefringent materials, such as chalcopyrite crystals. The analysis is verified in (110)-cut ZnGeP_2 and compared to (zincblende) GaP. Although the crystals share the same nonzero second-order tensor elements, the birefringence in chalcopyrite crystals cause the pump pulse polarization to evolve as it propagates through the crystal, resulting in a drastically different angular dependence in chalcopyrite crystals. The analysis is extended to {012}- and {114}-cut chalcopyrite crystals and predicts more efficient conversion for the {114} crystal cut over the {012}- and {110}-cuts.