Campuses:

Abnormal refraction of EM waves in periodic metamaterials

Wednesday, October 4, 2006 - 3:00pm - 3:50pm
EE/CS 3-180
Alexander Figotin (University of California)
Joint work with I Vitebskiy.

Wave propagation in spatially periodic media, such as photonic crystals,
can be qualitatively different
from any uniform substance. The differences are particularly pronounced
when the electromagnetic wavelength
is comparable to the minimal translation of the periodic structure. In
such a case, the periodic medium cannot
be assigned any meaningful refractive index. Still, such important
features as negative refraction and/or
opposite phase and group velocities for certain directions of light
propagation can be found in almost any
photonic crystal. The only reservation is that unlike hypothetical
uniform left-handed media, photonic crystals
are essentially anisotropic at frequency range of interest. Consider now
a plane wave incident on a semi-infinite photonic crystal. One can
assume, for instance, that in the case of positive refraction,
the normal components of the group and the phase velocities of the
transmitted Bloch wave have the same sign,
while in the case of negative refraction, those components have opposite
signs. What happens if the normal
component of the transmitted wave group velocity vanishes? Let us call
it a zero-refraction case.
At first sight, zero normal component of the transmitted wave group
velocity implies total reflection of the
incident wave. But we demonstrate that total reflection is not the only
possibility. Instead, the transmitted
wave can appear in the form of an abnormal grazing mode with huge
amplitude and nearly tangential group
velocity. This spectacular phenomenon is extremely sensitive to the
frequency and direction of propagation of
the incident plane wave. We also discuss some possible applications of
this effect.

REFERENCES:

- A. Figotin, and I. Vitebskiy. Phys. Rev. E68, 036609 (2003).

- J. Ballato, A. Ballato, A. Figotin, and I. Vitebskiy. Phys. Rev. E71,
(2005).
MSC Code: 
74Jxx
Keywords: