Extreme-Ultraviolet Vortices of very high Topological Charge

With widespread applications in optical trapping, super-resolution microscopy, quantum communications & information, and material processing, there is an ever-mounting interest in the generation and characterization of light beams carrying topological singularities [1] . An emblematic situation of this singular-optics is the Laguerre-Gauss laser modes presenting an azimuthal phase dependence: φ(r,θ)=l θ [2] . The integer l also called the topological charge of the singularity, is the number of 2π phase shifts along the azimuthal coordinate of the beam. This phase structure corresponds to a helicoidal wavefront and is often named an optical vortex. These helically phased beams are known to carry Orbital Angular Momentum (OAM). Besides, high-harmonic generation (HHG) in rare gases has proven to be an effective way to extend singular light beams to the extreme-ultraviolet (EUV) spectral range [3] , [4] . During HHG with a driver of charge l 1 , the momentum conservation results in a linear upscaling of the topological charge with harmonic order [2] : l q = ql 1 , where l q is the topological charge of q tℎ harmonic. In this work, we will present our recent results on the generation, and amplitude, phase, and modal content characterization of EUV vortices until l =100. Furthermore, we will support our experimental findings with simulation results [5] .