Optical vortices in brief: introduction for experimentalists Lyubomir Stoyanov, Suzana Topuzoski, Gerhard G. Paulus and Alexander Dreischuh Eur. Phys. J. Plus, 138 8 (2023) 702 Published online: 10 August 2023 DOI: 10.1140/epjp/s13360-023-04227-3