Multi-millijoule terahertz emission from laser-wakefield-accelerated electrons

Abstract

High-power terahertz radiation was observed to be emitted from a gas jet irradiated by 100-terawatt-class laser pulses in the laser-wakefield acceleration of electrons. The emitted terahertz radiation was characterized in terms of its spectrum, polarization, and energy dependence on the accompanying electron bunch energy and charge under various gas target conditions. With a nitrogen target, more than 4 mJ of energy was produced at <10 THz with a laser-to-terahertz conversion efficiency of ~0.15%. Such strong terahertz radiation is hypothesized to be produced from plasma electrons accelerated by the ponderomotive force of the laser and the plasma wakefields on the time scale of the laser pulse duration and plasma period. This model is examined with analytic calculations and particle-in-cell simulations to better understand the generation mechanism of high-energy terahertz radiation in laser-wakefield acceleration.

Generation of High-Power Terahertz Waves in a Collisional and Magnetized Plasma by Two-Color Femtosecond Laser Beams

“…To fully harness the benefits of simultaneous forward and backward THz radiation, it is essential to achieve precise control and optimization of the laser and plasma parameters. To implement the theoretical results presented in previous section and for simulations runs, the experimental parameters listed in references [21][22][23] were considered. A short laser pulse (> ‫)ݏ݂72‬ at ߣ = 800 ݊݉ wavelength with energy parameter < ‫ܬ7.2‬ was taken into consideration.…”

Toward high-power terahertz radiation sources based on ultrafast lasers

“…For gas plasma, direct THz generation is attributed to electron acceleration by laser ponderomotive force and wakefield effects. 49,58,59 In the case of liquid media, THz generation is interpreted through the formation of electric dipoles between electrons and ionized liquid molecules under laser ponderomotive force and space charge field. 60–62 In solid plasma, THz generation is explained by transient dipoles induced by transient currents of sideband electrons at the incident surface and forward transient electron bunch currents, 63–65 as well as ion acceleration in the plasma sheath formed by electron bunches exiting the rear side.…”

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

“…All these applications demand strong THz sources, and various methods have been developed to produce high-energy and/or high-intensity THz radiation. These include difference-frequency generation (DFG) 11 – 13 or optical rectification (OR) 14 – 17 of ultrafast laser pulses in nonlinear crystals, two-color laser mixing in gases 18 – 21 , laser-plasma interaction in liquids and solids 22 – 24 , coherent transition radiation (CTR) by ultrashort electron bunches 25 , laser-plasma accelerated electrons 26 , 27 , and more 28 , 29 .…”