Coherent Elegant Laguerre-Gaussian Beam Research Articles

Channel capacity of orbital-angular-momentum-based wireless communication systems with partially coherent elegant Laguerre-Gaussian beams in oceanic turbulence.

For practical wireless communication links, one of the critical challenges is the random fluctuation of turbulence that will impair link performance. Here a transmission model of partially coherent elegant Laguerre-Gaussian (ELG) beams in oceanic turbulence is established. An analytical formula for channel capacity of a partially coherent ELG beam propagating through a turbulent ocean is derived. The effects of oceanic turbulence on the evolution of channel capacity performance are studied quantitatively in a series of numerical simulations. Research results show that decreasing the rate of dissipation of mean-square temperature and ratio of temperature to salinity, as well as increasing the dissipation rate of turbulent kinetic energy per unit mass of fluid of a turbulent ocean can significantly improve communication channel capacity. Furthermore, choosing optimum beam source parameters is favorable to mitigate the influence of oceanic turbulence. Results also show that in the underwater turbulence, the partially coherent ELG beams are more affected by turbulence as compared to the fully coherent ELG beams. These study results may provide potential help in designing the free-space optical vortex communication systems.

Performance analysis of the OAM based optical wireless communication systems with partially coherent elegant Laguerre–Gaussian beams in oceanic turbulence

The transmission model of partially coherent elegant Laguerre–Gaussian (ELG) beams in oceanic turbulence is established by employing the spatial power spectrum of the refractive index of sea-water and the optics approximation. The mathematical expressions of mode probability, energy content, and orbital angular momentum (OAM) state detection probability for partially coherent ELG beams are obtained. The influences of beam and turbulence parameters on the propagation properties of light beam are illustrated in detail with numerical simulations. Results indicate that partially coherent ELG beams with smaller azimuthal mode, smaller OAM state difference, longer blue–green incident wavelength, and appropriate beam waist are less affected by turbulent ocean. Moreover, the evolution characteristics of laser beam may be able to keep a better quality under the condition of lower rate of dissipation of mean-square temperature, higher rate of dissipation of turbulent kinetic energy per unit mass of fluid, and smaller ratio of temperature to salinity for maritime environment. In addition, the partially coherent ELG beams exhibit more robust resistance to turbulence than the partially coherent standard Laguerre–Gaussian beams. These results are expected to be potential helpful in understanding the optical transmission process in turbulent media and designing the optical vortex communication systems.

Measuring topological charge of partially coherent elegant Laguerre-Gaussian beam.

The partially coherent elegant Laguerre-Gaussian (ELG) beam is of importance and exhibits extraordinary characteristics in many fields, such as optical communications and optical trapping. Here, we show a method to measure the topological charge of a partially coherent ELG beam. We find that the number of ring dislocations in the far-field complex degree of coherence is equal to the topological charge |l| of a partially coherent ELG beam, and which is confirmed experimentally. Our results will be useful for applications using partially coherent ELG beams.

Propagation of partially coherent Laguerre Gaussian beams through inhomogeneous turbulent atmosphere.

Analytical formulas for the root-mean-square (rms) spatial width, the rms angular width, and the M2-factor of partially coherent standard Laguerre Gaussian beams (PC-SLGBs) and partially coherent elegant Laguerre Gaussian beams (PC-ELGBs) in inhomogeneous turbulent atmosphere have been derived. The propagation properties of PC-SLGBs and PC-ELGBs in inhomogeneous atmospheric turbulence are studied numerically and comparatively. It can be found that the propagation of laser beams in inhomogeneous turbulence is different from that in homogeneous turbulence. It is also shown that relative rms spatial widths and M2-factors of PC-ELGBs are more affected by inhomogeneous turbulence than those of PC-SLGBs. Moreover, the relative rms spatial widths and M2-factors of PC-SLGBs and PC-ELGBs in inhomogeneous turbulent atmosphere are closely related with waist widths, coherence widths, zenith angles, inner scales, and beam orders. Furthermore, the saturation propagation distance of the relative M2-factor and rms angular width with zenith angles of π/6 are 20 km and 0.5 km, respectively.

Trapping two types of particles using a focused partially coherent elegant Laguerre–Gaussian beam

The radiation forces on a Rayleigh dielectric sphere induced by a focused partially coherent elegant Laguerre-Gaussian (ELG) beam are investigated by using the Rayleigh scattering theory. It is found that a focused partially coherent ELG beam with suitable mode orders can be used to trap a Rayleigh particle whose refractive index is larger or smaller than that of the ambient by varying its initial spatial coherence width. Therefore, one can use one optical-trap system to trap two types of particles with different refractive indices.