High efficiency and collimated terahertz pulse from ultra-short intense laser and cone target

We propose a new, to the best of our knowledge, method to radiate a high-efficiency and collimated terahertz (THz) pulse from a relativistic femtosecond laser and cone target. Particle-in-cell simulations demonstrate that a THz source of 40 mJ, pointing at an angle of ∼20 ^∘, can be generated from a laser pulse of 1.9 J by using a cone target whose open angle is 10 ^∘. The peak power of the THz pulse is 10^11 W. This method, which manipulates the divergence angle and the energy conversion efficiency of the THz source, should promote THz science into the extra strong region with a compact laser system.