Laser beam self-focusing in the atmosphere.
ABSTRACT We propose to exploit a self-focusing effect in the atmosphere to assist delivering powerful laser beams from orbit to the ground. We demonstrate through numerical modeling that when the self-focusing length is comparable with the atmosphere height the spot size on the ground can be reduced well below the diffraction limits without beam quality degradation. The density variation suppresses beam filamentation and provides the self-focusing of the beam as a whole. The use of light self-focusing in the atmosphere can greatly relax the requirements for the orbital optics and ground receivers.
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ABSTRACT: Using the weak nonparaxial approximation, we derive explicit analytical relationships for three projections of the electric field vector of a hypergeometric (HyG) laser beam. For the HyG beams with topological charge n = 0, 1 we derive explicit formulae for the axial intensity, which suggest that the waist position is related to the parameters of the HyG beam and shifted with respect to the plane z = 0. Such a displacement of the axial intensity peak has been given the name 'HyG beam lensless focusing' and formulae for calculating the said shift magnitude (focus distance) are deduced. The propagation of the HyG beam at n = 0 is simulated using the finite-difference time-domain method. The waist shift and the axial intensity magnitudes are shown to agree with those predicted by the approximate relations.Journal of optics 04/2011; 13(7):075703. · 2.01 Impact Factor
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ABSTRACT: We study the self-focusing and defocusing of a light beam carrying angular momentum (called twisted light) propa- gating in a nonlinear medium. We derive a differential equation for the beam width parameter f as a function of the propagation distance, angular frequency, beam waist and intensity of the beam. The method is based on the Wentzel-Kramers-Brillouin and the paraxial approximations. Analytical expressions for f are obtained, analyzed and illustrated for typical experimental situations.Optics Express 12/2010; 18(26):27691-6. · 3.55 Impact Factor