Intensity distribution properties of Gaussian vortex beam propagation in atmospheric turbulence

By using wave optics numerical simulation, the intensity-hole effect, beam spreading and wandering properties of Gaussian vortex beam propagation in atmospheric turbulence are investigated quantitatively. It is found that an intensity hole in the center of the beam pattern appears gradually as a Gaussian vortex beam propagates. The size of the intensity hole increases with the increase of the topological charge of the vortex phase. However, the intensity hole could to some extent be filled with optical energy by atmospheric turbulence, especially in strong turbulence. The radius of the intensity hole first decreases and then increases with the growth of turbulence strength. The effective radius of vortex beam with larger topological charge is greater than with a smaller topological charge. But the topological charge has no evident influence on beam wandering.

Propagation of the Bessel-Gaussian Beams Generated by Coherent Beam Combining in Oceanic Turbulence

Coherent beam combining(CBC)is recently used to generate high power vortex beams which are strongly required in specific applications.In this paper,based on the extended Huygens-Fresnel principle,the exact theoretical forms for the intensity distribution of CBC Bessel-Gaussian beams(BGBs)in turbulent ocean are derived.To show the superiority of CBC BGBs in turbulent channels,the comparison in the intensity evolution of CBC BGBs with ideal BGBs is performed.It is found that the beam spreading of CBC BGBs is smaller than that of ideal BGBs under the same oceanic turbulence conditions.Moreover,the effect of the beam parameters and channel parameters on the quality of CBC BGBs is also analyzed.The results show that the oceanic turbulence with a higher rate of dissipation of kinetic energy per unit mass of fluid,lower dissipation rate of the mean-squared temperature,or smaller ratio of temperature and salinity contributions to the refractive index spectrum has smaller impact on CBC BGBs.Moreover,the increasing number of the beamlets,the increasing waist width of each beamlet,and the decreasing radius of the beam distribution cause the optical energy to be more concentrated,and thus leading to a longer non-diffraction propagation distance.

Transverse beam size measurement system using visible synchrotron radiation at HLS II

An interferometer system and an imaging system using visible synchrotron radiation（SR） have been installed in the Hefei Light Source（HLS） II storage ring. Simulations of these two systems are given using Synchrotron Radiation Workshop（SRW） code. With these two systems, the beam energy spread and the beam emittance can be measured. A detailed description of these two systems and the measurement method is given in this paper. The measurement results of beam size, emittance and energy spread are given at the end.

THE ANGULAR SPREAD OF THE DEFLECTED SAW BEAM DIFFRACTED BY BRAGG GRATING

In this paper , the angular spread of the SAW beam diffracted by Bragg grating , denoted by δθ1 ,is analysed based on the equations of the deflection angle and the deflection effciency . A parameter δθB is defined to refer to ' Bragg angular spectrum width ' of the grating . The importance of this parameter in distinguishing the angular spread range of the deflected beam for different regimes is discussed as well. It is show from the analysis that if the spread angle of the incident beam labelled with δθinc is larger than the ' Bragg witdth of the angular spectrum ' of the grating , the spread angle δθ1 of the deflected beam will equal to δθB ; but if the angular divergence of the incident beam is less than δθB , then δθ1 =δθinc.Experimentally , four kinds of samples with different configurations are investigated by optical method , two of which operate in the regime of δθinc<<δθB and the others correspond to the case in the regime of δθinc >>δθB . The widths of the angular spread of the incident beam and the deflected beam are estimated by measuring the widths of their own acousto - optical diffraction points . It is demonstrated that the experimental results agree with the theoretical results approximately .