Archimedes spiral beam: composite of a helical-axicon generated Bessel beam and a Gaussian beam

Abstract

This paper introduces a structured beam with Archimedes spiral intensity distribution. The Archimedes spiral (AS) beam is the composite of a helical-axicon generated (HAG) Bessel beam and a Gaussian (GS) beam. We observed the spiral intensity patterns using computational holography, achieving the tuning over spiral arms number and spiral spacing. Analyzing the propagation dynamics of AS beams, we present that the spiral intensity will reverse beyond the maximum diffraction-free distance. Before and after the beam reverse, the spiral spacing remains constant, but the spiral direction is opposite. In addition, we obtain the Archimedes spiral equations to describe the spiral intensity patterns. Unlike the beams with Fermat and hyperbolic spiral patterns, the intensity distributions of AS beams are isometrically spiral. The isometric spiral intensity makes it possible to form particle isometric channels. AS beams have potential application prospects in particle manipulation, microscopic imaging, and laser processing.