Fig. 1. Schematic of THz radiation driven by space charge field induced by pondermotive force

Fig. 2. Calculations and experimental results^[25]. (a) FIR radiation calculated according to Eq. (1) when n= 10¹⁹ cm^-3; (b) transformation relationship between electronic scintillator detector signal and terahertz radiation

Fig. 3. Schematic of the model and experimental results^[26]. (a) Schematics of the experimental setup; (b) relationship between two laser pre pulses and main laser pulse; (c) maximum proton energy and THz radiation signal for ASE durations of 0, 2 ns, and 4 ns; (d) current radiation terahertz waves formed by the movement of electrons along the target surface

Fig. 4. Experimental setup and experimental results^[23]. (a) Schematics of the experimental setup; (b) measured THz time-domain and frequency-domain signals in the experiment; (c) relationship between THz energy and pump laser energy; (d) electron current distributions at the target surface at the time of 50, 60, and 70 laser cycles obtained from 2D PIC simulations

Fig. 5. Schematic of THz radiation from the self-organized transient fast electron currents

Fig. 6. Experimental setup and experimental results^[9]. (a) Schematics of the experimental setup; (b) measured THz time-domain signal in the experiment; (c) THz spectrum

Fig. 7. Schematic of THz radiation generated by the transient electrostatic sheath field

Fig. 8. Schematic of the model and experimental results. (a) Schematic of the linear mode conversion model^[27]; (b) schematic of the experimental setup^[27]; (c) dependence of the THz radiation pulse energy on target laser energy in experimental results^[28]; (d) experimental results and PIC simulation results on relationship between THz energy and the preplasma scale length^[28]

Fig. 9. Schematic of linear mode conversion model^[28]

Fig. 10. Experimental setup and experimental results^[33]. (a) Schematic of the experimental setup; (b) THz spectral distribution measured with band-pass filters (blue circles) and the theoretically fitted spectrum; (c) comparison between measured (blue circles) and calculated (red curve) angular distributions of THz radiation; (d) dependence of THz energy and electron temperature T_e measured by changing the target laser energy on the charge Q of the escaping electron beam behind the target

Fig. 11. Schematic of the THz-generation scenarios at the rear side of a laser-irradiated foil ^[34]

Fig. 12. Experimental setup and experimental results. (a) Schematic of the experimental setup; (b) dependence of the THz energy on the wire length; (c) spectra and temporal waveforms of the THz pulses when the wire diameter was varied from 50 μm to 90 μm; (d) angular distribution of THz emission from a 50 μm-diameter wire in the horizontal plane^[42]