Reversed propagation dynamics of Laguerre-Gaussian beams in left-handed materials

On the basis of angular spectrum representation, the reversed propagation dynamics of a Laguerre-Gaussian beam in left-handed materials (LHMs) is presented. We show that the negative phase velocity gives rise to a reversed screw of the wave front, and ultimately leads to a reversed rotation of the optical vortex. Furthermore, the negative Gouy-phase shift causes an inverse spiral of the Poynting vector. It is found that the Laguerre-Gaussian beam in LHMs will present the same propagation characteristics as the counterpart with opposite topological charges in regular right-handed materials (RHMs). The momentum conservation theorem ensures that the tangential component of the wave momentum at the RHM-LHM boundary is conserved. It is shown that although the linear momentum reverses its direction, the angular momentum remains unchanged.