Formation of optical vortices using coherent laser beam arrays.pdf

Formation of optical vortices using coherent laser beam arrays Li-Gang Wang,1, 2 * Li-Qin Wang,1 and Shi-Yao Zhu 1, 2, 3 1 Department of Physics, Zhejiang University, Hangzhou 310027, China 2 Department of Physics, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong, China 3Department of Physics, Hong Kong Baptist Univerisity, Kowloon Tong, Hong Kong, China *Corresponding author:sxwlg@ Abstract: We present a novel proposal to generate an optical vortex beam by using the coherent-superposition of multi-beams in a radial symmetrical configuration. In terms of the generalized Huygens-Fresnel diffraction integral, we have derived the general propagation expression for the coherent radial laser arrays. Based on the derived formulae, we have analyzed the effects of the beamlet number N , the separation distance ρ of the beamlets and the topological charge m on the intensity and phase distributions of the resulted beams. Our simulation results show that optical vortices could be efficiently formed and generated due to the interference and superposition effect of all the beamlets, during the propagation process of the coherent radial laser arrays with the initial well-organized phase distributions through the free space. In the focusing system, the resulted beam near the focusing plane has the strong rotation effect with the phase helicity. ?2008 Optical Society of America OCIS codes: (140.3300) Laser beam shaping; (350.5030) Phase; (260.3160) Interference; (260.1960) Diffraction theory. References and links 1. J. F. Nye and M. V. Berry, “Dislocations in wave trains,” Proc. R. Soc. London Ser. A 336, 165 (1974). 2. J. F. Nye, Natural focusing and fine structure of light：caustics and wave dislocations (Institute of Physics Publishing, 1999). 3. A. Mair, A. Vaziri, G. Weihs, and A. Zeilinger, “Entanglement of the orbital angular momentum states of photon,” Nature 412, 313 (2001). 4. L. Allen, M. W. Beijersbergen, R. J. C. Spreeuw,