Browsing by Author "Ji, Xiaoling"

Now showing 1 - 7 of 7

Citation - WoS: 9
Citation - Scopus: 10
Changes of the centroid position of laser beams propagating through an optical system in turbulent atmosphere
(Elsevier Sci Ltd, 2013) Ji, Xiaoling; Baykal, Yahya; Jia, Xinhong; 7812; Elektrik-Elektronik Mühendisliği
In this paper, the effects of atmospheric turbulence, initial field amplitude, optical system and thermal blooming on the centroid position of laser beams propagating through the atmosphere are studied in detail. With the average over the ensemble of the turbulent medium, the centroid position is independent of turbulence. However, the centroid position depends on the centroid positions at the source plane and in the far-field, and the elements of ray-transfer-matrix. The physical reason why the centroid position changes on propagation is that the far-field centroid position is not located on the propagation z-axis due to the field phase distortion and the decentred intensity. The centroid position of laser beams with the spherical aberration and the decentred intensity is examined analytically. When laser beams with the decentred intensity propagate through the atmosphere, the effect of thermal blooming on the centroid position is investigated by using the four-dimensional (4D) computer code of the time-dependent propagation of high power laser beams through the atmosphere. (C) 2013 Elsevier Ltd. All rights reserved.
Citation - WoS: 15
Citation - Scopus: 15
Field correlations of annular beams in extremely strong turbulence
(Elsevier Science Bv, 2012) Baykal, Yahya; Cai, Yangjian; Ji, Xiaoling; 7812; Elektrik-Elektronik Mühendisliği
The field correlations of annular beams are formulated when the atmosphere assumes extremely strong turbulence. Thicker and larger ring sized annular beams are found to exhibit larger absolute field correlations. For the same transverse distance at the receiver plane, annular beams attain larger field correlations if the transverse distance starts from the receiver origin. Comparisons of the annular beam absolute field correlations in extremely strong turbulence with the no turbulence results show that the absolute field correlation variations follow similar trends, except that the magnitudes of the absolute field correlations are much smaller in extremely strong turbulence and the annular fields become decorrelated at very short transverse distances. When the inner scale of turbulence becomes smaller, the absolute field correlations of the annular beams in extremely strong turbulence become smaller. (C) 2012 Elsevier B.V. All rights reserved.
Citation - WoS: 66
Influence of turbulence on the effective radius of curvature of radial Gaussian array beams
(Optical Soc Amer, 2010) Ji, Xiaoling; Eyyuboglu, Halil T.; Baykal, Yahya; 7688; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
The analytical formula for the effective radius of curvature of radial Gaussian array beams propagating through atmospheric turbulence is derived, where coherent and incoherent beam combinations are considered. The influence of turbulence on the effective radius of curvature of radial Gaussian array beams is studied by using numerical calculation examples. (C) 2010 Optical Society of America
Citation - WoS: 74
Citation - Scopus: 78
Propagation of an Airy beam through the atmosphere
(Optical Soc Amer, 2013) Ji, Xiaoling; Eyyuboglu, Halil T.; Ji, Guangming; Jia, Xinhong; 7688; Elektronik ve Haberleşme Mühendisliği
In this paper, the effect of thermal blooming of an Airy beam propagating through the atmosphere is examined, and the effect of atmospheric turbulence is not considered. The changes of the intensity distribution, the centroid position and the mean-squared beam width of an Airy beam propagating through the atmosphere are studied by using the four-dimensional (4D) computer code of the time-dependent propagation of Airy beams through the atmosphere. It is shown that an Airy beam can't retain its shape and the structure when the Airy beam propagates through the atmosphere due to thermal blooming except for the short propagation distance, or the short time, or the low beam power. The thermal blooming results in a central dip of the center lobe, and causes the center lobe to spread and decrease. In contrast with the center lobe, the side lobes are less affected by thermal blooming, such that the intensity maximum of the side lobe may be larger than that of the center lobe. However, the cross wind can reduce the effect of thermal blooming. When there exists the cross wind velocity v(x) in x direction, the dependence of centroid position in x direction on v(x) is not monotonic, and there exists a minimum, but the centroid position in y direction is nearly independent of v(x). (C) 2013 Optical Society of America
Citation - WoS: 8
Citation - Scopus: 8
Radius of curvature of Bessel and modified Bessel Gaussian beams
(Elsevier Science Bv, 2013) Eyyuboglu, Halil Tanyer; Ji, Xiaoling; 7688; Elektronik ve Haberleşme Mühendisliği
We analyze the radius of curvature of Bessel Gaussian (BG) and modified Bessel Gaussian (mBG) beams. The study is based on the results of analytic derivation as well as those of the random phase screen approach. Our results are displayed in graphs as variations of radius of curvature against propagation distance at various settings of beam order, width parameter, source focal length, wavelength, refractive index structure constant. Our findings indicate that mBG beams, in general will have larger radius of curvature values than BG beams. It is further observed that increases in beam order will lead to greater radius of curvatures. Rises in the width parameter will reveal more the differentiations between BG and mBG beams. At small focal lengths, the difference between BG and mBG beams is hardly noticeable. Higher wavelengths will initially cause a reduction in the radius of curvature, but at longer propagation distances, the reverse will happen. Increases in the refractive index structure constant will lead to smaller radius of curvature values. A general agreement is found in comparing the analytic results of BG beams with those of phase screen approach. (C) 2013 Elsevier B.V. All rights reserved.
Citation - WoS: 21
Citation - Scopus: 22
Scintillations of higher order laser beams in anisotropic atmospheric turbulence
(Optical Soc Amer, 2016) Baykal, Yahya; Luo, Yujuan; Ji, Xiaoling; 7812; Elektrik-Elektronik Mühendisliği
The scintillation index of higher order laser beams is examined when such beams propagate in anisotropic atmospheric turbulence. Anisotropy is introduced through non-Kolmogorov atmospheric turbulence. The scintillation index results are obtained by employing the Rytov method solution; thus the results are valid for weak anisotropic atmospheric turbulence and for horizontal links. Variations in the scintillations are shown for various higher order laser modes against the changes in the optical source size, power law exponent of anisotropic non-Kolmogorov spectrum, anisotropic factors, and link length. Our results can be used in the design of optical wireless communication systems used between airplanes. (C) 2016 Optical Society of America
Citation - WoS: 108
Citation - Scopus: 124
Wave structure function and spatial coherence radius of plane and spherical waves propagating through oceanic turbulence
(Optical Soc Amer, 2014) Lu, Lu; Ji, Xiaoling; Baykal, Yahya; 7812; Elektrik-Elektronik Mühendisliği
The analytical formulae for the wave structure functions (WSF) and the spatial coherence radius of plane and spherical waves propagating through oceanic turbulence are derived. It is found that the Kolmogorov five-thirds power law of WSF is also valid for oceanic turbulence in the inertial range. The changes of the WSF and the spatial coherence radius versus different parameters of oceanic turbulence are examined. (C) 2014 Optical Society of America.