Multilevel axicon for perfect optical vortex generation

Rebeca Tudor,Andrei Avram,Cristian Kusko,Mihai Kusko,O Fähnle,A Vasdekis

doi:10.1051/epjconf/201921502003

Abstract

We present the fabrication of a beam shaper with 32 levels for the generation of nondiffractive optical fields representing quasi-Bessel beams of order zero. This optical element is designed for visible light (λ=633 nm) and fabricated using standard photolithography and a fine calibrated reactive ion etching process. A large number of levels approximates a continuous conical surface so that the optical quality of the element is very good. It is investigated the possibility of generating perfect optical vortices with this class of optical elements.

Highlights

Ideal Bessel beams are nondiffractive optical fields described by invariant intensity profiles along an infinite propagation distance
One can generate only quasi-Bessel beams characterized by finite focal extensions and intensity profiles that vary along the propagation axis but only after a specific distance called focal length
We investigated the optical quality of the fabricated axicon with the optical microscope

Summary

Introduction

Ideal Bessel beams are nondiffractive optical fields described by invariant intensity profiles along an infinite propagation distance. One can generate only quasi-Bessel beams characterized by finite focal extensions and intensity profiles that vary along the propagation axis but only after a specific distance called focal length. Quasi-Bessel beams can be generated with conical lens, planar Pancharatnam-Berry phase elements, spatial light modulator, Fresnel lens-based elements [1,2,3,4]. Nondiffractive unique beams are widely exploited in fields like optical trapping [5], beam shaping [6,7,8,9] optical communications [10,11], microscopy [12]

Fabrication process

Structural characterization

Conclusions