Enhanced optical angular momentum in cylinder waveguides with negative-index metamaterials

The optical angular momentum (AM) of helical electromagnetic (EM) modes in cylinder waveguides with negative-index metamaterials (NIM) is investigated. The AM density in NIM is shown to be negative valued with respect to the azimuthal mode index, in sharp contrast to that in regular dielectrics and vacuum. Furthermore, the AM flux per single-photon flux is found to be greatly enhanced in the NIM waveguides; its value depends on the form of EM momentum used in the AM. This interesting phenomenon is shown to be associated with the unique trapped EM modes in the NIM waveguides. Our investigation results could contribute to many potential applications, especially in realizing high density optical memory and buffers, and in solving the Abraham-Minkowski dilemma.