Beam wander of J 0- and I 0-Bessel Gaussian beams propagating in turbulent atmosphere (original) (raw)
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Atmospheric and Oceanic Propagation of Electromagnetic Waves IV, 2010
In this paper we review our work done in the evaluations of the root mean square (rms) beam wander characteristics of the flat-topped, dark hollow, cos-and cosh Gaussian, J 0 -Bessel Gaussian and the I 0 -Bessel Gaussian beams in atmospheric turbulence. Our formulation is based on the wave-treatment approach, where not only the beam sizes but the source beam profiles are taken into account as well. In this approach the first and the second statistical moments are obtained from the Rytov series under weak atmospheric turbulence conditions and the beam size are determined as a function of the propagation distance. It is found that after propagating in atmospheric turbulence, under certain conditions, the collimated flat-topped, dark hollow, cos-and cosh Gaussian, J 0 -Bessel Gaussian and the I 0 -Bessel Gaussian beams have smaller rms beam wander compared to that of the Gaussian beam. The beam wander of these beams are analyzed against the propagation distance, source spot sizes, and against specific beam parameters related to the individual beam such as the relative amplitude factors of the constituent beams, the flatness parameters, the beam orders, the displacement parameters, the width parameters, and are compared against the corresponding Gaussian beam.
We investigate the propagation characteristics of truncated Bessel-modulated Gaussian beams in turbulence. Based on the extended Huygens-Fresnel integral formula in the paraxial approximation, an approximate analytical axial intensity of the considered beams family is formulated. By using our theoretical results, numerical examples are given to illustrate the axial intensity distribution in turbulence which is compiled numerically for different beam parameters and for different values of the turbulence strength. Our result is very accurate in the far field, because the use of the paraxial approximation and by using the expression of the hard-edge aperture function expanded as a sum of finite-term complex Gaussian function.
Long-distance Bessel beam propagation through Kolmogorov turbulence
Journal of the Optical Society of America A, 2015
Free space optical communication has the potential to transmit information with both high speed and security. However, since it is unguided it suffers from losses due to atmospheric turbulence and diffraction. To overcome the diffraction limits the long distance propagation of Bessel beams is considered and compared against Gaussian beam properties. Bessel beams are shown to have a number of benefits over Gaussian beams when propagating through atmospheric turbulence.
Beam wander analysis for focused partially coherent beams propagating in turbulence
Optical Engineering, 2012
We extend the theory of beam wander for propagation through atmospheric turbulence to the case of a focused partially coherent beam (PCB). In addition to investigating the beam wander expression, we restate expressions for the beam size, long-and short-time average beam intensity profile, and the on-axis scintillation index of tracked and untracked beams. A wave optics simulation is implemented and the numerical results are compared with corresponding analytic results. The cases examined involve turbulence strengths ranging from C 2 n ¼ 10 −16 to 10 −14 m −2∕3 and for various horizontal paths ranging from 1 to 10 km. Although the extended analytic theory stems from a study of coherent beams, the simulation results show good agreement with the analytical results for PCBs in fluctuation regimes ranging from weak to intermediate.
2010
Laser beam propagation in maritime environment is particularly challenging, not only for scattering and absorption due to high humidity, but also for a different behavior of atmospheric turbulence with respect to terrestrial propagation. Recently, a new power spectrum for the fluctuations of the refractive index in the Earth's atmosphere has been introduced to describe maritime atmospheric turbulence. This maritime power spectral model shows a characteristic bump, similar to Hill's bump, that appears when the product between the wavenumber and the inner scale is around unity, 0 1 l N. In this paper, under weak turbulence conditions, we use the mentioned maritime power spectrum to analyze long term beam spread, beam wander and Strehl ratio of a Gaussian beam wave propagating through maritime atmospheric turbulence.
Bessel Gaussian Beam Propagation through Turbulence in Free Space Optical Communication
Optical Memory and Neural Networks, 2018
This paper investigated the experimental demonstration of jitter analysis for Bessel Gaussian beam propagation through the atmospheric turbulence conditions using two different wavelength lasers such as red and green laser. Axicon lens is used to generate Bessel Gaussian beam experimentally and different modulation schemes such as PAM, PPM, PWM, ASK, BPSK and QPSK are used to analyze the phase and time jitter. The Plano-Convex type Axicon is used to create a ring shaped approximation of a Bessel Gaussian beam which increases in diameter over distance while retaining a constant ring thickness. In this BG beam propagation, for red laser the noted phase jitter value is 45.196 radians in ASK and for green laser 36.955 radians in with turbulence conditions. Hence the lower wavelength BG laser beam (green laser) is more energetic than the lower wavelength BG laser beam (red laser).
Average intensity and spreading of an elegant Hermite–Gaussian beam in turbulent atmosphere
Optics Express, 2009
The propagation of an elegant Hermite-Gaussian beam (EHGB) in turbulent atmosphere is investigated. Analytical propagation formulae for the average intensity and effective beam size of an EHGB in turbulent atmosphere are derived based on the extended Huygens-Fresnel integral. The corresponding results of a standard Hermite-Gaussian beam (SHGB) in turbulent atmosphere are also derived for the convenience of comparison. The intensity and spreading properties of EHGBs and SHGBs in turbulent atmosphere are studied numerically and comparatively. It is found that the propagation properties of EHGBs and SHGBs are much different from their properties in free space, and the EHGB and SHGB with higher orders are less affected by the turbulence. What's more, the SHGB spreads more rapidly than the EHGB in turbulent atmosphere under the same conditions. Our results will be useful in long-distance free-space optical communications.
Optical Engineering, 2007
Failure of the first-order Rytov approximation to properly predict the scintillation index of a large-aperture focused beam, or an uplink collimated ͑or focused͒ beam, has been discussed in several recent publications, which cite beam wander effects as the main reason for this failure. We use computer simulations to examine several aspects of beam wander phenomena on a propagating convergent beam in the weak-fluctuation regime over a horizontal path at high altitude for which the refractive index structure parameter is on the order of C n 2 = 1.39 ϫ 10 −16 m −2/3. Simulation results are presented at various ranges up to 10 km for ͑1͒ the beam wander centroid displacement, ͑2͒ the kurtosis excess of the irradiance profile, ͑3͒ the irradiance profile, ͑4͒ the meansquare hot spot displacement from the boresight and from the centroid, and ͑5͒ the scintillation index at the optical axis of the beam. In addition, simulation results are compared with theoretical models.
Propagation characteristics of higher-order annular Gaussian beams in atmospheric turbulence
Optics Communications, 2006
The propagation characteristics of higher-order annular Gaussian (HOAG) beams in turbulence are investigated. From a HOAG source plane excitation, the average intensity of the receiver plane is developed analytically. This formulation is verified against the previously derived HOAG beam solution in free space. The graphical outputs indicate that, upon traveling in turbulent atmosphere, the HOAG beam will undergo different stages of evolution. At intermediate propagation distances, it will attempt to concentrate the energy near the origin. In this process, the appearance of the single higher-order primary beam will be encountered. Eventually HOAG originated beam will become a pure Gaussian beam after propagating an excessive distance in the turbulent medium.