Extreme Ultraviolet Fractional Orbital Angular Momentum Beams from High Harmonic Generation

Abstract

We investigate theoretically the generation of extreme-ultraviolet (EUV) beams carrying fractional orbital angular momentum. To this end, we drive high-order harmonic generation with infrared conical refraction (CR) beams. We show that the high-order harmonic beams emitted in the EUV/soft x-ray regime preserve the characteristic signatures of the driving beam, namely ringlike transverse intensity profile and CR-like polarization distribution. As a result, through orbital and spin angular momentum conservation, harmonic beams are emitted with fractional orbital angular momentum, and they can be synthesized into structured attosecond helical beams –or “structured attosecond light springs”– with rotating linear polarization along the azimuth. Our proposal overcomes the state of the art limitations for the generation of light beams far from the visible domain carrying non-integer orbital angular momentum and could be applied in fields such as diffraction imaging, EUV lithography, particle trapping, and super-resolution imaging.

Attosecond twisted beams from high-order harmonic generation driven by optical vortices

“…Thus, they are perfect candidates to exchange OAM in situations where not only the phase possesses a helical structure (like standard OAM beams), opening an entire new light-matter interaction regime. New regimes, in which the non-perturbative behavior of HHG imprints a relevant signature in the generated attosecond twisted beams [41] , or where harmonics with both OAM and spin angular momentum are generated [53] , remain to be explored.…”

Comment on Half-Integer Quantum Numbers for the Total Angular Momentum of Photons in Light Beams with Finite Lateral Extensions

“…The findings of Ref. [2] were already used in later papers, for instance on the generation of half-integer orbital angular momentum beams [5] or on fundamentals and applications of conical refraction [6].…”

Generation of light beams with custom orbital angular momentum and tunable transverse intensity symmetries

“…Custom values of OAM, e.g. fractional values [6], have been realized in the optical spectrum using plasmonic vortex elements [7], whereas in the extreme ultraviolet spectrum through high harmonic generation [8]. An application of fractional OAM is shown by Alexeyev et al [9], where they study the propagation of a fractional vortex beam through an optical fiber.…”