Impact of dispersion, free carriers, and two-photon absorption on the generation of intense terahertz pulses in ZnTe crystals

Abstract

We study the evolution of the energy and the spectrum of a terahertz wave generated by optical rectification of an ultrashort laser pulse in ZnTe crystals with different thicknesses. As the pump intensity increases, we observe a shift in the terahertz spectrum toward lower frequencies. Moreover, at high pump intensities, in disagreement with common sense, thin crystals have a better conversion efficiency than thicker ones. These phenomena are accounted for by the pump depletion induced by two-photon absorption, pulse broadening and the impact of the photoinduced free carriers on the complex refractive index of the crystal in the terahertz range.

Mechanisms of THz generation from silver nanoparticle and nanohole arrays illuminated by 100 fs pulses of infrared light

“…For OR one might expect a second-order dependence. For OR a strict second-order dependence is usually only observed for very low incident intensities, as processes such as two-photon absorption lead to a lower-order dependence as the incident intensity is increased [36].…”

Indication of Te segregation in laser-irradiated ZnTe observed by in situ coherent-phonon spectroscopy

“…[15][16][17] The 3.6-THz resonance was also observed in coherent-phonon spectroscopy, 18-20 but its origin is still a matter of debate. [16][17][18][19][20] Note that ZnTe has a relatively large cross section for twophoton absorption (TPA), 21,22 which limits its efficiency for THz wave generation. 23 This drawback, however, might turn into a benefit in terms of material modification using femtosecond laser pulses.…”

Second‐Harmonic and Terahertz Generation in a Prussian‐Blue Analogue

“…We have also evaluated the capability of this material to generate terahertz (THz) waves. Indeed, like ZnTe, a crystal widely used to generate THz pulses, [12][13][14] this material belongs to the 43m space group. Accordingly, one may wonder if THz generation cannot be recorded in Rb 0.94 Mn[Fe(CN) 6 ] 0.98 ·0.3H 2 O.…”