Orbital angular momentum from semiconductor high-order harmonics

TL;DR

This paper demonstrates the transfer of orbital angular momentum from a laser to high-order harmonics generated in semiconductor crystals, enabling the creation of nanoscale optical vortices with potential applications in quantum technologies.

Contribution

It verifies OAM transfer in semiconductor HHG and introduces a method to generate focused optical vortices using etched spiral structures on zinc oxide crystals.

Findings

OAM is conserved from laser to harmonics in solids.

Spiral etching creates nanoscale optical vortices.

Potential for nanoscale optical trapping and quantum manipulation.

Abstract

Light beams carrying orbital angular momentum (OAM) have led to stunning applications in various fields from quantum information to microscopy. In this letter, we examine OAM from the recently discovered high-harmonic generation (HHG) in semiconductor crystals. HHG from solids could be a valuable approach for integrated high-flux short-wavelength coherent light sources. The solid state nature of the generation medium allows the possibility to tailor directly the radiation at the source of the emission and offers a substantial degree of freedom for spatial beam shaping. First, we verify the fundamental principle of the transfer and conservation of the OAM from the generation laser to the harmonics. Second, we create OAM beams by etching a spiral zone structure directly at the surface of a zinc oxide crystal. Such diffractive optics act on the generated harmonics and produces focused optical vortices with nanometer scale sizes that may have potential applications in nanoscale optical trapping and quantum manipulation.