Wide bandwidth THz emission based on two color chirped laser plasma interaction

Abstract

This study examined the impact of chirping the input pulses on the amplification of a wide bandwidth THz wave emitted from a plasma slab within a range of input wavelengths from 800 nm to 3.9 µm. It was found that in a normal case of interaction when the injected pulses are highly chirped, flowerthorn-like fluctuations raised in the transverse current density of the plasma, and a THz emission with a higher amplitude within a wide band of 50 THz could be reached. Employing the cross-focusing scheme, the amplitude of the THz wave at 3.9 µm is further enhanced to about 43 times the ones obtained at 800 nm when the two-color pulses are weakly chirped down to 3 × 10−4 rad/s2. A significant increase of 233 times received in THz radiation when a weakly-chirped regime of delayed cross-focusing interaction is established and the intensity of the delayed pulse is increased to 1015 W/cm2, beyond the ionization threshold of Argon gas. The profile change of the fundamental and its second-harmonic waves indicated that a flat-top form is capable of enhancing the THz amplitude approximately by 8 times compared to the case when an ordinary Gaussian profile is used. The obtained results have confirmed that a combination of the type of interaction, chirp value, and the profile of inputs is crucial for enlarging the THz magnitude and domain.