Enhancing electromagnetic radiations by a pre-ablation laser during laser interaction with solid target

Ultra-short untraintense laser interacting with solid targets can produce significant electromagnetic pulses (EMPs), which are strongly pertinent to laser and target parameters. In this study, EMPs' generation due to pulsed laser (30 fs, 6×1019 W/cm2) irradiating aluminum foils are recorded and analyzed. The experimental results indicate a pre-ablation pulse (200 ps, 1×1012 W/cm2) that tends to enhance the electromagnetic emission inside the target chamber and the diagnostic cavity. The largest EMP signal is obtained when the pre-ablation pulse is incident on the target at 100 ps prior to the main laser beam. Meanwhile, the frequencies of EMPs are broadened up to 2 GHz in the diagnostic cavity in the 100 ps delayed case, indicating that EMPs with higher frequencies can be generated if the most energetic electrons are accelerated. The simulating results verify expansion of the pre-plasmas induced by the pre-ablation laser, which is beneficial to lift both the energy and quantity of hot electrons escaping from the target, accounting for the ehancement of EMPs. The resulting conclusions offer a new avenue to generate intense EMPs, which can be potentially used in nondestructive examination, high-power microwave source, and energy transfer.