Application of a binary curved fork grating for the generation and detection of optical vortices outside the focal plane
Svetlana N. Khonina, Andrey V. Ustinov, Mikhail S. Kirilenko, Aleksandr A. Kuchmizhak, Alexey P. Porfirev
Abstract
In this paper, we consider using a binary curved fork grating not only for the simultaneous formation of several Bessel vortex beams but also for detecting the presence of angular harmonics (optical vortices) in an analyzed beam outside the focal plane. In this case, we use the effect of a longitudinal shift of focus (or correlation peak) when the lens is supplemented with an axicon. The combination of a lens and an axicon provides, in the focal plane, the generation of narrow light rings whose radii do not depend on the vortex phase component. Thus, the detection of an optical vortex cannot be carried out in the focal plane, but only at a certain distance from it, which provides additional security for information transmission. In addition, the use of these gratings makes it possible to simultaneously manipulate microparticles in various planes, and they can be used for fabricating complex three-dimensional metastructures as well as the single-shot pulse laser processing of transparent materials or polymers.