Extinction of coherent backscattering by a disordered photonic crystal with a Dirac spectrumR. A. Sepkhanov1, A. Ossipov2 and C. W. J. Beenakker1
1 Instituut-Lorentz, Universiteit Leiden - P.O. Box 9506, 2300 RA Leiden, The Netherlands, EU
2 School of Mathematical Sciences, University of Nottingham - University Park, Nottingham, NG7 2RD, UK, EU
received 1 October 2008; accepted in final form 9 December 2008; published January 2009
published online 16 January 2009
Photonic crystals with a two-dimensional triangular lattice have a conical singularity in the spectrum. Close to this so-called Dirac point, Maxwell's equations reduce to the Dirac equation for an ultrarelativistic spin-1/2 particle. Here we show that the half-integer spin and the associated Berry phase remain observable in the presence of disorder in the crystal. While constructive interference of a scalar (spin-zero) wave produces a coherent backscattering peak, consisting of a doubling of the disorder-averaged reflected photon flux, the destructive interference caused by the Berry phase suppresses the reflected intensity at an angle which is related to the angle of incidence by time reversal symmetry. We demonstrate this extinction of coherent backscattering by a numerical solution of Maxwell's equations and compare with analytical predictions from the Dirac equation.
42.25.Dd - Wave propagation in random media.
42.25.Hz - Interference.
42.70.Qs - Photonic bandgap materials.
© EPLA 2009