Controllable Spatial Array of Bessel-Like Vortical Optical Needles With Different Topological Charges and Locations in the Transverse Plane

Abstract

Bessel vortices generated via axicons are widely used for various applications like optical tweezers or laser microfabrication of transparent materials. The specific intensity profile having high aspect ratios of beam width and length, in turn, generates a high aspect ratio void that resembles an optical needle or an optical bottle. In contrast to commonly generated Bessel vortices, which have a fixed axial intensity distribution. We present a novel method for engineering Bessel vortices that can have an arbitrary axial intensity distribution via superposition of different cone-angle Bessel vortices. We analytically describe spatial spectra of optical needle-like vortices having an arbitrary axial intensity distribution. We also demonstrate a superposition of independent optical Bessel-like vortices and analyze the physical limitations to observe well-separated optical needles as they are influenced by mutual interference of the individual beams. To verify our theoretical and numerical results, we generate controllable spatial arrays of individual beams with various numbers and spatial separations by altering the spectrum of the incoming laser beam via the spatial light modulator. Lastly, we numerically examine distortions caused by propagation through the planar air-dielectric interface and show the compensation method by appropriately modifying the spectral masks.