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Ultrafast Terahertz Metadevices
In article number 2104275, Jiangang Liang, Chunhai Fan, Chao Chang, and co‐workers present a germanium hybrid metallic metasurface under dual‐stimulus control. Photoexcitation of germanium film enables 100% modulation depth of Fano resonance and ultrafast switching time within 10 ps. By adding current‐bias, the pump threshold to modulate the metasurface is greatly reduced...
Arming metasurface with active materials furnishes a feasible solution to dynamically control over terahertz (THz) waves, which is extremely significant for the realization of upcoming sixth generation telecommunications. However, the present active materials are mainly limited to single external driving field, hindering the capability of metasurface for flexible manipulation of THz waves. Besides,...
We establish a one-to-one mapping between the local phase slip and the spatial position near the focus by scanning a thin jet along the propagation direction of laser beams. The measurement shows that the optimal phase of THz can be utilized to characterize in situ the spatially dependent relative phase of the two-color field and the carrier-envelope-phase of the few-cycle pulse. The result is of...
Air-plasma is a common and convenient way to obtain intense and broad-band terahertz (THz) wave in laboratory. However, less attention has been paid on the plasma effect to the generated THz wave. To give a more comprehensive understanding, we characterize the transmitting property of air-plasma at THz frequency range. Resonant absorption of air-plasma is identified. The polarization dependence of...
We demonstrate experimentally that terahertz generation from ionizing gas in the two-color fields with co-rotating circular polarization is five times stronger than that with usually linear polarization.
We present in situ measurements of the relative phase shift induced by Gouy phase shift near the focus in two-color field. The good agreement between the measurement and the theoretical prediction shows that the optimal phase of THz is robust enough as an useful tool to measure the relative phase change.
We experimentally demonstrated that the circularly polarized two-color femtosecond pulses with the same helicity can effectively enhance terahertz intensity by a factor of 5 in comparison with the linearly polarized counterparts. The quantum mechanical simulations confirm this enhancement based on the analysis of residual current calculated by time-dependent Schrödinger equation in three dimensions...
Synchronizing high-harmonics and terahertz-wave spectroscopy (HATS) has been demonstrated as an efficient approach in revealing the information of molecular structure and the underlying electron dynamics. We further investigate the alignment dependent HATS from carbon dioxide at different dual-color relative phases (DRP). We find that the alignment dependence of terahertz generation dose not vary...
We report the joint measurements of terahertz wave and high harmonic spectra generated from aligned nitrogen molecules. Our results show the yields of terahertz wave and high harmonics are sensitive to the alignment angle. This observation clarifies that electronic structure play an important role in the generation of terahertz and high harmonics from molecules.
We demonstrate an enhancement of terahertz wave generation from plasma produced by circularly polarized two-color fields when the laser intensity is high enough to saturately ionize the gas. Comparing to the linear two-color fields, the conversion efficiency of co-rotating circularly polarized two color-fields is about 40% higher.
We study the generation of terahertz (THz) radiation from atoms and molecules driven by an ultrashort fundamental laser and its second harmonic field by solving time-dependent Schrödinger equation. The simulations show that the initial wave-packet and its subsequent acceleration in the laser field, and rescattering with long-range Coulomb potential play key roles on THz generation. We also present...
We perform a joint measurement of terahertz waves, high-harmonics and the second harmonic interference generated by ionizing atomic Argon gas in a thin jet moving along the Releigh range of a phase-locked two-color laser field. The measurements show that the optimal phases for terahertz radiation and even-order harmonics change simultaneously along the focal length but the the relative phase between...
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