Studies of powerful terahertz radiation from laser-produced plasmas

Recently Terahertz (THz) radiation from laser-produced plasmas has attracted much interest since plasmas can work at an arbitrarily high laser intensity. We will present the generation of strong THz radiation from femtosecond and picosecond relativistic laser-plasma interactions. THz pulses with energies up to >200 μJ/sr have been demonstrated. The temporal waveform, polarization, and angular distribution are measured. We find that the radiation depends on the preplasma density scale length. The THz radiation is probably attributed to the self-organized transient fast electron currents formed along the target surface when the plasma density profile is steep, while, the linear mode conversion when a large preplasma is formed.