Diffraction of relativistic vortex harmonics with fractional average orbital angular momentum

Vortex harmonics with fractional average orbital angular momentum are genera ted when a relativistic fractional vortex beam is incident on and reflected from an over-dense plane plasma target. A two-step model is presented to explain the far-field patterns of the harmonics. In the Erst step, a fundamental spot-shaped hole is produced during the hole-boring stage, and harmonics are genera ted simultaneously. In the second step, differen t oTder harmonics are diffracted by the hole and propagate to the far field. This process can be accurately described by the Fraunhofer diffraction theory. This work facilitates a basic recognition of fractional vortex beams.

Vortex harmonics with fractional average orbital angular momentum are generated when a relativistic fractional vortex beam is incident on and reflected from an over-dense plane plasma target. A two-step model is presented to explain the far-field patterns of the harmonics. In the first step, a fundamental spot-shaped hole is produced during the hole-boring stage, and harmonics are generated simultaneously. In the second step, different order harmonics are diffracted by the hole and propagate to the far field. This process can be accurately described by the Fraunhofer diffraction theory. This work facilitates a basic recognition of fractional vortex beams.