arXiv subjects

M. W. McCall

Publications and source records attributed to M. W. McCall.

4 recordsLinked to original sources

arXiv2014

Negative refraction in active and passive media: a discussion of various criteria

There are three widely-used conditions for characterizing negative refraction in isotropic dielectric-magnetic materials. Here we demonstrate that whilst all the different conditions are equivalent for purely passive media, they are distinct if active media are considered. Further, these criteria can also be applied to negative refraction in acoustic materials, where we might replace the dielectric permittivity $ε$ with a bulk modulus $κ$, and the magnetic permeability $μ$ with the mass density $ρ$.

physics.optics↗

arXiv2008

Causality-based criteria for a negative refractive index must be used with care

Using the principle of causality as expressed in the Kramers-Kronig relations, we derive a generalized criterion for a negative refractive index that admits imperfect transparency at an observation frequency $ω$. It also allows us to relate the global properties of the loss (i.e. its frequency response) to its local behaviour at $ω$. However, causality-based criteria rely the on the group velocity, not the Poynting vector. Since the two are not equivalent, we provide some simple examples to compare the two criteria.

physics.optics↗

arXiv2004

Counterposed phase velocity and energy-transport velocity vectors in a dielectric-magnetic uniaxial medium

When a plane wave is launched from a plane surface in a linear, homogenous, dielectric-magnetic, uniaxial medium, we show that its phase velocity and the energy-transport velocity vectors can be counterposed (i.e., lie on different sides of the surface normal) under certain circumstances.

physics.optics↗

arXiv2002

The negative index of refraction demystified

We study electromagnetic wave propagation in mediums in which the effective relative permittivity and the effective relative permeability are allowed to take any value in the upper half of the complex plane. A general condition is derived for the phase velocity to be oppositely directed to the power flow. That extends the recently studied case of propagation in mediums for which the relative permittivity and relative permeability are both simultaneously negative, to include dissipation as well. An illustrative case study demonstrates that in general the spectrum divides into five distinct regions.

physics.class-ph↗