Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDigital sorting perturbed laguerre-gaussian beams by radial numbers via high order intensity moments
146
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Thus, the results of our studies lie in developing and implementing the basic principles of digital sorting the Laguerre-Gauss modes by radial numbers both for a non-degenerate and a degenerate state of a vortex beam subject to perturbations in the form of a hard-edged aperture of variable radius. The digital sorting of LG beams by the orthogonal basis involves the use of higher-order intensity moments, and subsequent scanning of the modulated beam images at the focal plane of a spherical lens. As a result, we obtain a system of linear equations for the squared mode amplitudes and the cross amplitudes of the perturbed beam. The solution of the equations allows one to determine the amplitudes of each LG mode and restore both the real mode array and the combined beam as a whole. First, we developed a digital sorting algorithm, and then two types of vortex beams were experimentally studied on its basis: a single LG beam and a composition of single LG beams with the same topological charges(azimuthal numbers) and different radial numbers . The beam was perturbed by means of a circular hard-edged aperture with different radii R. As a result of the perturbation, a set of secondary LG modes with different radial numbers k is appeared that is characterized by an amplitude spectrum . The spectrum obtained makes it possible to restore both the real array of LG modes and the perturbed beam itself with a degree of correlation not lower than. As a measure of uncertainty induced by the perturbation we measured the informational entropy (Shannons entropy)
rate research
Read More
We found that small perturbations of the optical vortex core in the Laguerre-Gaussian (LG) beams generate a fine structure of the Hermite-Gauss (HG) mode spectrum. Such perturbations can be easily simulated by weak variations of amplitudes and phases of the HG modes in the expansion of the LG beam field. We also theoretically substantiated and experimentally implemented a method for measuring the topological charge of LG beams with an arbitrary number of ring dislocations. Theoretical discussion and experimental studies were accompanied by simple examples of estimating the orbital angular momentum and the topological charge of perturbed LG beams.
We have investigated the generation of highly pure higher-order Laguerre-Gauss (LG) beams at high laser power of order 100W, the same regime that will be used by 2nd generation gravitational wave interferometers such as Advanced LIGO. We report on the generation of a helical type LG33 mode with a purity of order 97% at a power of 83W, the highest power ever reported in literature for a higher-order LG mode.
Laguerre-Gaussian (LG) beam has orbital angular momentum (OAM). A particle trapped in an LG beam will rotate about the beam axis, due to the transfer of OAM. The rotation of the particle is usually in the same direction as that of the beam OAM. However, we discovere that when the LG beam is strongly focused, the rotation of the particle and the beam OAM might be in the opposite direction. This anomalous effect is caused by the negative torque on the particle exerted by the focused LG beam, which is similar to the optical pulling force in the linear case. We calculated the scattering force distribution of a micro-particle trapped in an optical tweezers formed by the strongly focused LG beam, and showed that there exist stable trajectories of the particle that controlled by the negative torque. We proposed several necessary conditions for observing the counter-intuitive trajectories. Our work reveals that the strongly trapped micro-particle exhibits diversity of motion patterns.
A generalized family of scalar structured Gaussian modes including helical-Ince--Gaussian (HIG) and Hermite--Laguerre--Gaussian (HLG) beams is presented with physical insight upon a hybrid topological evolution nature of multi-singularity vortex beams carrying orbital angular momentum (OAM). Considering the physical origins of intrinsic coordinates aberration and the Gouy phase shift, a closed-form expression is derived to characterize the general modes in astigmatic optical systems. Moreover, a graphical representation, Singularities Hybrid Evolution Nature (SHEN) sphere, is proposed to visualize the topological evolution of the multi-singularity beams, accommodating HLG, HIG and other typical subfamilies as characteristic curves on the sphere surface. The salient properties of SHEN sphere for describing the precise singularities splitting phenomena, exotic structured light fields, and Gouy phase shift are illustrated with adequate experimental verifications.
The transverse structure of light is recognized as a resource that can be used to encode information onto photons and has been shown to be useful to enhance communication capacity as well as resolve point sources in superresolution imaging. The Laguerre-Gaussian (LG) modes form a complete and orthonormal basis set and are described by a radial index p and an orbital angular momentum (OAM) index l. Earlier works have shown how to build a sorter for the radial index p or/and the OAM index l of LG modes, but a scalable and dedicated LG mode sorter which simultaneous determinate p and l is immature. Here we propose and experimentally demonstrate a scheme to accomplish complete LG mode sorting, which consists of a novel, robust radial mode sorter that can be used to couple radial modes to polarizations, an l-dependent phase shifter and an OAM mode sorter. Our scheme is in principle efficient, scalable, and crosstalk-free, and therefore has potential for applications in optical communications, quantum information technology, superresolution imaging, and fiber optics.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
