Orbital Angular Momentum Density of an Elegant Laguerre-Gaussian Laser Beam in the Source Region.

Based on the method of the vectorial angular spectrum of a laser beam, an analytical expression of the electric field of an elegant Laguerre-Gaussian laser beam in source region is derived without any approximation, and the corresponding magnetic field is obtained by taking the curl of the electric field. By using the obtained expressions of the electromagnetic fields, the orbital angular momentum density of the elegant Laguerre-Gaussian laser beam can be accurately calculated. The effects of the angular mode number, the radial mode number and the linearly polarized angle as well as the beam waist width on the distribution of the orbital angular momentum density of the elegant Laguerre-Gaussian laser beam are investigated, respectively. Also, the orbital angular momentum density distribution of the propagating part of the elegant Laguerre-Gaussian laser beam is compared with that of the whole laser beam. Upon propagation, the orbital angular momentum density difference between the propagating part and the whole laser beam decreases. This research is beneficial to the optical manipulation with an elegant Laguerre-Gaussian laser beam. [ABSTRACT FROM AUTHOR]