Open AccessGeneration of an optical needle beam with a laser inscribed Pancharatnam-Berry phase element under imperfect conditions
Author(s) -
Pavel Gotovski,
Paulius Šlevas,
Sergej Orlov,
Orestas Ulčinas,
Antanas Urbas
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.438709
Subject(s) - optics , optical axis , conical surface , axicon , perpendicular , grating , bessel beam , polarization (electrochemistry) , physics , laser , beam (structure) , materials science , laser beams , lens (geology) , geometry , chemistry , mathematics , composite material
Beams exhibiting long focal lines and small focal spot sizes are desired in a variety of applications and are called optical needles, with Bessel beams being a common example. Conical prisms are regularly used to generate Bessel beams, however, this method is usually plagued by an appearance of on-axis oscillations. In this work, we consider an optical element based on the space-domain Pancharatnam-Berry phase (PBP) to generate a high-power optical needle with a smooth and constant on-axis intensity profile. The phase in PBP elements is not introduced through optical path differences but results from the geometric phase that accompanies space-variant polarization manipulation. Our implementation is based on a type 2 modification of bulk transparent glass material, resulting in the formation of nanogratings with slow axes aligned perpendicular to the grating corrugation. We investigate both numerically and experimentally the stability of an optical needle generation under imperfect conditions. Influences of misalignments in the optical schema are investigated numerically and experimentally.