TY - JOUR

T1 - Generation of high-OAM ultraviolet twisted light for RF-photoinjector applications

AU - Dyatlov, A. S.

AU - Dolgintsev, D. M.

AU - Gerasimov, V. V.

AU - Kobets, V. V.

AU - Nazmov, V. P.

AU - Nozdrin, M. A.

AU - Sergeev, A. N.

AU - Shokin, D. S.

AU - Yunenko, K. E.

AU - Karlovets, D. V.

N1 - This study was supported by the Russian Science Foundation, Russia (Project No. 23-62-10026).

PY - 2026/11

Y1 - 2026/11

N2 - The generation of relativistic vortex electron beams via photoemission requires ultraviolet (UV) laser beams with well-controlled orbital angular momentum (OAM) compatible with radio-frequency (RF) photoinjector drive-laser systems. However, achieving high-OAM beam generation in the deep UV with sufficient efficiency, stability, and mode control remains technically challenging. Here, we experimentally demonstrate the generation of high-OAM (up to ℓ=64ħ) UV vortex beams at 266 nm using three types of fabricated diffractive optical elements integrated into an operational photoinjector drive-laser system: a reflective fork grating, a high-topological-charge spiral phase plate, and binary axicons. The spiral phase plate produces a high-purity Laguerre–Gaussian mode with a conversion efficiency of 80%, while fork gratings provide flexible access to lower-order OAM states and enable robust modal diagnostics. In contrast, binary axicons generate low-divergence quasi-Bessel beams that can be interpreted as controlled superpositions of multiple OAM states with a finite OAM bandwidth. The generated beams are characterized using cylindrical-lens mode conversion and radial intensity analysis, demonstrating controlled generation of both near-pure OAM eigenstates and broadband OAM distributions in the UV regime. These results provide a comparative, application-driven framework for selecting UV-compatible OAM generation techniques and establish a practical route toward structured photocathode illumination in high-brightness RF photoinjectors.

AB - The generation of relativistic vortex electron beams via photoemission requires ultraviolet (UV) laser beams with well-controlled orbital angular momentum (OAM) compatible with radio-frequency (RF) photoinjector drive-laser systems. However, achieving high-OAM beam generation in the deep UV with sufficient efficiency, stability, and mode control remains technically challenging. Here, we experimentally demonstrate the generation of high-OAM (up to ℓ=64ħ) UV vortex beams at 266 nm using three types of fabricated diffractive optical elements integrated into an operational photoinjector drive-laser system: a reflective fork grating, a high-topological-charge spiral phase plate, and binary axicons. The spiral phase plate produces a high-purity Laguerre–Gaussian mode with a conversion efficiency of 80%, while fork gratings provide flexible access to lower-order OAM states and enable robust modal diagnostics. In contrast, binary axicons generate low-divergence quasi-Bessel beams that can be interpreted as controlled superpositions of multiple OAM states with a finite OAM bandwidth. The generated beams are characterized using cylindrical-lens mode conversion and radial intensity analysis, demonstrating controlled generation of both near-pure OAM eigenstates and broadband OAM distributions in the UV regime. These results provide a comparative, application-driven framework for selecting UV-compatible OAM generation techniques and establish a practical route toward structured photocathode illumination in high-brightness RF photoinjectors.

KW - Diffractive optical elements

KW - Orbital angular momentum

KW - Rf-photoinjector

KW - Structured light

KW - Vortex electron beams

UR - https://www.scopus.com/pages/publications/105039869109

UR - https://www.mendeley.com/catalogue/8b5d6807-3a5d-3cc7-859d-b84ad6f13bf6/

U2 - 10.1016/j.optcom.2026.133388

DO - 10.1016/j.optcom.2026.133388

M3 - Article

VL - 617

JO - Optics Communications

JF - Optics Communications

SN - 0030-4018

M1 - 133388

ER -