Influence of Two-Photon Absorption Anisotropy on Terahertz Emission Through Optical Rectification in Zinc-Blende Crystals

• DOI: 10.1007/s10762-018-0468-4
• Publication Date: 2018-01-29T04:38:53Z
• Authors: Federico Sanjuan; Gwenaël Gaborit; Jean-Louis Coutaz
• Keywords: [SPI.ELEC]Engineering Sciences [physics]/Electromagnetism; [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics]; [SPI.PLASMA]Engineering Sciences [physics]/Plasmas; [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic; 0202 electrical engineering, electronic engineering, information engineering; 02 engineering and technology

We report for the first time on the observation of an angular anisotropy of the THz signal generated by optical rectification in a ZnTe crystal. This cubic (zinc-blende) crystal in the orientation exhibits both transverse isotropy for optical effects involving the linear χ(1) and nonlinear χ(2) susceptibilities. Thus, the observed anisotropy can only be related to χ(3) effect, namely two-photon absorption, which leads to the photo-generation of free carriers that absorb the generated THz signal. Two-photon absorption in zinc-blende crystals is known to be due to a spin-orbit interaction between the valence and higher-conduction bands. We perform a couple of measurements that confirm our hypothesis, as well as we fit the recorded data with a simple model. This two-photon absorption effect makes difficult an efficient generation, through optical rectification in zinc-blende crystals, of THz beams of any given polarization state by only monitoring the laser pump polarization.