Focused-laser-beam scintillations in the turbulent atmosphere

Banakh, V. A.; Krekov, G. M.; Миронов, В. Л.; Khmelevtsov, S. S.; Tsvik, Ruvim Sh.

doi:10.1364/josa.64.000516

Cited by 63 publications

(17 citation statements)

References 4 publications

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“…These include Gaussian [1][2][3][4][5][6], flat-topped [7][8][9], annular [11], sinusoidal-Gaussian [11][12][13], dark hollow [14], laser array [15], Bessel [16][17][18] and astigmatic [19,20] beams. Comprehensive presentations of scintillation results can be found in [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Partially coherent off-axis Gaussian beam scintillations

Baykal

Eyyuboğlu

Cai

2010

Journal of Modern Optics

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The scintillation index at the receiver origin is formulated for a partially coherent off-axis Gaussian beam in atmospheric turbulence by employing the extended Huygens-Fresnel principle. Our formula correctly reduces to the existing coherent and partially coherent Gaussian beam scintillation indices in the limiting cases. For off-axis Gaussian beams with imaginary, real and complex displacement parameters, the scintillation index reduces when the incidence becomes more incoherent. When the source size of the off-axis Gaussian beam increases, the scintillations increase for partially coherent sources and decrease for incoherent sources, the tendency being observed for imaginary, real and complex displacement parameters. For the fully coherent off-axis Gaussian beams, increase in the source size first causes an increase in the scintillations, eventually reaching saturation at large source sizes, the increase is not monotonic and may exhibit a peak around the Fresnel zone sized off-axis Gaussian sources. For all degrees of partial coherence, off-axis beams possessing imaginary displacement parameters exhibit larger scintillations when the displacement parameter increases for large sized incidences, however, for small sized incidences, scintillations stay at the same level when the imaginary displacement parameter increases, the fixed scintillation value being lower for more incoherent sources. For off-axis Gaussian sources possessing real displacement parameters, this behavior is reciprocal with respect to the source size, i.e. for all degrees of partial coherence, off-axis beams possessing real displacement parameters exhibit larger scintillations when the displacement parameter increases for small sized incidences, and for large sized incidences, scintillations stay at the same level when the real displacement parameter increases, the fixed scintillation value again being lower for more incoherent sources. For all degrees of partial coherence, off-axis Gaussian beams possessing imaginary displacement parameters exhibit larger scintillations than the off-axis Gaussian beams possessing real displacement parameters when the absolute value of displacement parameter increases for large sized incidences.

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Section: Introductionmentioning

confidence: 99%

Partially coherent off-axis Gaussian beam scintillations

Baykal

Eyyuboğlu

Cai

2010

Journal of Modern Optics

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“…(5), and calculating phase in the geometrical optics approximation along the straight lines connecting the source and observation points [33][34][35]:…”

Section: Other Versions Of the Ehfmentioning

confidence: 99%

Extended Huygens–Fresnel principle and optical waves propagation in turbulence: discussion

Charnotskii¹

2015

J. Opt. Soc. Am. A

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Extended Huygens-Fresnel principle (EHF) currently is the most common technique used in theoretical studies of the optical propagation in turbulence. A recent review paper [J. Opt. Soc. Am. A31, 2038 (2014)JOAOD60740-323210.1364/JOSAA.31.002038] cites several dozens of papers that are exclusively based on the EHF principle. We revisit the foundations of the EHF, and show that it is burdened by very restrictive assumptions that make it valid only under weak scintillation conditions. We compare the EHF to the less-restrictive Markov approximation and show that both theories deliver identical results for the second moment of the field, rendering the EHF essentially worthless. For the fourth moment of the field, the EHF principle is accurate under weak scintillation conditions, but is known to provide erroneous results for strong scintillation conditions. In addition, since the EHF does not obey the energy conservation principle, its results cannot be accurate for scintillations of partially coherent beam waves.

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“…10,11 Some of these work cover focused beams. 2,3,9 It is known that focused beam scintillations yield favourable results over the collimated counterparts for Gaussian beams. 4 By employing the log-amplitude correlation functions of general-type beams 12 , we have developed a formula to express the scintillation index of general-type beams in weak turbulence and reported results that cover cos-Gaussian, annular 13 and cosh-Gaussian beam scintillations.…”

Section: Introductionmentioning

confidence: 99%

Intensity fluctuations of focused general-type beams in atmospheric optics links

Baykal

Eyyuboğlu

2007

SPIE Proceedings

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The intensity fluctuations of focused general-type beams in weakly turbulent atmospheric links are formulated and numerically evaluated. Focused general-type beams in general cover very large range of beams, however in this work we concentrate specifically on the focused sinusoidal-Gaussian, annular and flat-topped beams. The behavior of the scintillations for these beams is examined versus the focusing distance, wavelength of operation and the source size. In our formulation, atmospheric turbulence is introduced through the Rytov method where the free space field (i.e., in the absence of turbulence) at the receiver plane for the general-type focused beam is found by utilizing the Huygens-Fresnel principle. Figures are presented showing the scintillation index for focused general-type beams and collimated generaltype beams. To find out the source and medium parameters that will yield favourable scintillation levels, the intensity fluctuations of the focused sinusoidal-Gaussian, annular and flat-topped beams are compared. Within the range of selected source and medium parameters, our observations indicate that the intensity fluctuations in weak turbulence tend to be the smallest for the focused flat-topped Gaussian beams and the largest for the focused cos-Gaussian beams. Gaussian, cosh-Gaussian and annular beams experience interim level fluctuations. The comparison of the scintillation levels for the mentioned types of focused beams follow the same tendency for all the propagation distances. Also, the intensity fluctuations of the focused general-type beams in turbulence are compared with their collimated counterparts. Such a comparison reveals that for all the beams at a selected source size, the scintillations are nearly the same for both the focused and the collimated cases at all the propagation distances, except for the flat-topped Gaussian beams. When focused flat-topped Gaussian beams are employed, the intensity fluctuations seem to be lower as compared to the equivalent collimated flat-topped Gaussian beam at shorter link lengths.

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Focused-laser-beam scintillations in the turbulent atmosphere

Cited by 63 publications

References 4 publications

Partially coherent off-axis Gaussian beam scintillations

Partially coherent off-axis Gaussian beam scintillations

Extended Huygens–Fresnel principle and optical waves propagation in turbulence: discussion

Intensity fluctuations of focused general-type beams in atmospheric optics links

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