Observation of terahertz nonlinear absorption activity in AlO.

We investigate the terahertz (THz) nonlinear absorption characteristics in a thin AlO crystal using nonlinear THz spectroscopy. A THz saturable absorption performance with a high modulation depth (27.5%) and a relatively low saturable intensity (6.

Terahertz-triggered ultrafast nonlinear optical activities in two-dimensional centrosymmetric PtSe.

The nonlinear mechanisms of polarization and optical fields can induce extensive responses in materials. In this study, we report on two kinds of nonlinear mechanisms in the topological semimetal PtSe crystal under the excitation of intense terahertz (THz) pulses, which are manipulated by the real and imaginary parts of the nonlinear susceptibility of PtSe. Regarding the real part, the broken inversion symmetry of PtSe is achieved through a THz-electric-field polarization approach, which is characterized by second harmonic generation (SHG) measurements.

Gigahertz electromagnetic pulse emission from femtosecond relativistic laser-irradiated solid targets.

The interactions between high-intensity laser and matter produce particle flux and electromagnetic radiation over a wide energy range. The generation of extremely intense transient fields in the radio frequency-microwave regime has been observed in femtosecond-to-nanosecond laser pulses with 10-10-W/cm intensity on both conductive and dielectric targets. These fields typically cause saturation and damage to electronic equipment inside and near an experimental chamber; nevertheless, they can also be effectively used as diagnostic tools.