Subcycle Extreme Nonlinearities in GaP Induced by an Ultrastrong Terahertz Field

Abstract

We report on the experimental observation of extreme laser spectral broadening and a change in optical transmission in gallium phosphite induced by 25 MV/cm terahertz (THz) single-cycle internal field. Such intense THz radiation leads to twofold transient modifications of the optical properties in the electro-optical crystal. First, the electric field provokes extensive cross-phase modulation via the χ^{(2)} and χ^{(3)} nonlinearities on a copropagating 50 fs near infrared laser pulse which turns into 500% spectral broadening. Second, we observe an instantaneous change of the optical transmission occurring at the THz field which is alleged to interband Zener tunneling and charge carrier density modification by impact ionization turning the semiconductor in a metal-like transient state. The presented scheme displays a pathway to coherently control the optical properties of semiconductors on an ultrafast time scale by a strong THz field.

Observation of extremely efficient terahertz generation from mid-infrared two-color laser filaments

“…To illustrate the strength of the THz fields generated by the mid-infrared filaments, we conducted a pump-probe experiment on nonlinear cross-phase modulation (XPM) of a THz pump and a visible probe pulse inside a 1 mm zinc telluride (ZnTe) crystal. Previously, similar XPM experiments were reported by Shen et al 55,56 in ZnTe and by Vicario et al 57 in GaP crystals.…”

“…6c shows that the central frequency of the probe pulse initially undergoes a red shift which then gives way to a blue shift, both about 12 nm. These shifts are proportional to the first derivative of the THz field 55,57 (see the blue line in Fig. 6c).…”

High Kerr nonlinearity of water in THz spectral range

“…Despite the growing interest to this issue, the observations of nonlinearities in THz region were carried out without using direct measurements of material properties in most cases. The latter ones can be nonlinearity and dispersion in the wave propagation, nonlinear optical response caused by intense ultrashort THz pulses [10], absorption bleaching by means of pump-probe technique [11,12], nonlinear free-carrier response [13,14], field-induced transparency [15], spin response [16], giant cross phase modulation and THz-induced spectral broadening of femtosecond pulses [17], quadratic THz optical nonlinearities by measuring the quadratic THz Kerr effect [18].…”

Artificial Generation of High Harmonics via Nonrelativistic Thomson Scattering in Metamaterial

“…With a Gaussian pulsed plane wave at 2.0 THz incident from the top, the temporal response of the metamaterial was then simulated. The peak amplitude of the incident electric field was set as 1×10 7 V/m, corresponding to the power density of 1.3×10 7 W/cm 2 , which is orders of magnitude lower than the general requirement of the conventional nonlinear [28,31,32]. As shown in Figure 3(a), we examined a y polarized transmission spectrum in frequency domain, which is transformed from the time response of the metamaterial by Fourier transformation ( Figure S2).…”