Gouy phase of optical beams in anisotropic indefinite metamaterials.

The Gouy phase shift of optical beams in anisotropic indefinite metamaterials displays extraordinary characteristics because of the presence of anisotropic magnetic and electric responses. We propose a simple interpretation of these characteristics from the unusual dispersion relation of the optical waves in the metamaterials, which influences the expectation value of the axial propagation constant of the focused beam.