Optimization of extreme ultraviolet vortex beam based on high harmonic generation

In high harmonic generation (HHG), Laguerre-Gaussian (LG) beams are used to generate extreme ultraviolet (XUV) vortices with well-defined orbital angular momentum (OAM), which have potential applications in fields such as microscopy and spectroscopy. An experimental study on the HHG driven by vortex and Gaussian beams is conducted in this work. It is found that the intensity of vortex harmonics is positively correlated with the laser energy and gas pressure. The structure and intensity distribution of the vortex harmonics exhibit significant dependence on the relative position between the gas jet and the laser focus. The ring-like structures observed in the vortex harmonics, and the interference of quantum paths provide an explanation for the distinct structural characteristics. Moreover, by adjusting the relative position between the jet and laser focus, it is possible to discern the contributions from different quantum paths. The optimization of the HH vortex field is applicable to the XUV, which opens up a new way for exploiting the potential in optical spin or manipulating electrons by using the photon with tunable orbital angular momentum.