Low Divergence Structured Beam In View Of Precise Long-Range Alignment

¹ Technical University of Liberec, 46117 Liberec, Czech Republic
² Institute of Plasma Physics of the Czech Academy of Sciences, Toptec Department, 51101 Turnov, Czech Republic
³ CERN – European Organization for Nuclear Research, 1211 Geneva 23, Switzerland

^* Corresponding author: miroslav.sulc@tul.cz

Published online: 13 October 2022

Abstract

A new method of generation of a Structured Laser Beam (SLB) with non-diverging central core was proposed and is promising for creating long distance multipoint alignment systems. This beam is generated by a set-up consisting of two convex lenses in Kepler telescope arrangement. The first one is a high refractive index ball lens, second one is a standard lens. The beam, in cross-section consisting of light and dark concentric circles, propagates over a large distance. The central core of the SLB has a very small divergence which can be tuned. A divergence of 10 μrad was proven experimentally. In this experiment, the small initial beam core diameter of 10 μm, and its diameter of 1.5 mm at a distance of 150 m, show its ability for use as a multipoint fiducial reference line. This small beam divergence seemingly lies beyond the diffraction limit for laser beams.