%0 Journal Article
%T Spin and Orbital Angular Momenta of Electromagnetic Waves in Free Space
%A Masud Mansuripur
%J Physics
%D 2012
%I arXiv
%R 10.1103/PhysRevA.84.033838
%X We derive exact expressions, in the form of Fourier integrals over the (k,w) domain, for the energy, momentum, and angular momentum of a light pulse propagating in free space. The angular momentum is seen to split naturally into two parts. The spin contribution of each plane-wave constituent of the pulse, representing the difference between its right- and left-circular polarization content, is aligned with the corresponding k-vector. In contrast, the orbital angular momentum associated with each plane-wave is orthogonal to its k-vector. In general, the orbital angular momentum content of the wavepacket is the sum of an intrinsic part, due, for example, to phase vorticity, and an extrinsic part, r_CM x p, produced by the linear motion of the center-of-mass r_CM of the light pulse in the direction of its linear momentum p.
%U http://arxiv.org/abs/1205.5900v1