Light beams may carry both a spin and an orbital angular momentum (OAM). While the former is associated to their polarization state, the latter stems from the geometrical properties of their wavefront. In their prototypical form, beams with OAM have “donuts-like” intensity profile and helicoidal wavefront, carrying integral multiples of ℏ as angular momenta. Since their “rediscovery” in the late 90’s, beams with OAM of visible wavelengths have found innumerable applications in quantum optics, microscopy or information transfer. A major recent development was the generation of such beams with much smaller wavelengths – in the extreme ultraviolet (XUV) - using synchrotron sources, free electron lasers as well as high harmonic sources (HHG).
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