THz wave generation from air plasma induced by vortex beam

In recent years, the technology of terahertz (THz) source has developed rapidly. Due to the advantages of long-distance generation and non-damage thresholds, THz wave generation from the air plasma excited by femtosecond laser attracted global attention. Since the first time the method was proposed, it has experienced many tremendous developments and leaps. In this letter, we propose a new method to generate THz wave with higher intensity. We demonstrate that the energy of THz wave can be effectively enhanced when the air plasma excited by a vortex beam. The energy of THz wave induced by two-color laser field generated through a 100-mm-thick BBO crystal is recorded by using a Golay detector. By comparing the intensity and spatial distribution of THz wave generated by different orders of vortex beams, we find that the energy of THz wave generated from low-order vortex beams is stronger than that from Gaussian beams with the invariant laser energy. To understand the effect of the vortex beam on the generation of THz wave, we compared the distribution of the focal plane between the Gaussian beam and the vortex beam. We believe this method can pave the way for finding the type of laser beam which can produce a stronger THz wave.