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We simultaneously observed both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a thin-foil target. The maximum proton energy of ∼2.3 MeV and an intense THz radiation were observed at the pulse duration of ∼30 fs. We also measured the proton beam and UV harmonics from a thin-foil target by changing the laser pulse duration. In the case of the ∼500 fs, peaks of UV harmonics up to fourth order appeared. This unique combination of the multiple beams will provide useful applications such as pump-probe experiments.

We demonstrate laser-ion acceleration from a near-critical density plasma, using amplified spontaneous emission (ASE) to convert a solid foil target into a lower-density target. In order to investigate the target density dependence of the laser-ion acceleration, two cases were investigated for which the ASE intensity differed by three orders of magnitude. In the low contrast case the beam centre for higher energy protons is shifted closer to the laser-propagation direction of 45○, while the centre of lower-energy beam remains near the target normal direction. We show that a near-critical density plasma can be used to control proton beam direction based on its energy.

We have demonstrated highly efficient broadband amplification by an optical parametric chirped pulse amplifier (OPCPA) system that uses high energy seed pulses. The OPCPA consists of three type I B-barium borate (BBO) crystals pumped by a Q-switched Nd:YAG laser. We successfully amplified the microjoule level seed pulses to 78 mJ with a pump-to-signal optical conversion efficiency of 26% at a 10 Hz repetition rate. To our knowledge these results represent the most optically efficient OPCPA to date pumped by a typical Q-switched laser.