Anomalous Group Velocity in a 3D Photonic Nanostructure

M. BOTEY, L. A. DORADO, R. A. DEPINE, G. LOZANO, H. MÍGUEZ, J. MARTORELL

Munich, Germany

Congreso; CLEO/Europe-EQEC 2009, The European Conference on Lasers and Electro-Optics and the XI European Quantum Electronics Conference; 2009

In recent years, a growing interest appeared in the systems that can provide a either a reduction of the speed of light, slow-light, or a superluminal light propagation. Experiments have confirmed the existence of both behaviors in three-dimensional ordered nanostructures, in the spectral range where the wavelength of light is on the order, or smaller, than the lattice constant [1]. Using periodic boundary conditions in a band structure calculation of a perfect 3D photonic crystal one finds that, in such frequency range, only propagating modes with a vanishing slope dispersion relation exist and, hence, a reduced group velocity is predicted [2]. In the present paper, we study such group velocity behavior for finite thin artificial opal slabs made of a reduced number of layers. In our model extinction is included. We consider light propagation in the GL direction of an fcc close-packed opal film made of polystyrene spheres. We determine the group velocity and group index of the electromagnetic waves from the linear response of the crystal, in the high energy spectral region. The vector KKR method we use to calculate light propagation [3,4] allows us to determine the phase delay introduced to the forwardly transmitted electromagentic fields from the finite photonic structure we consider. We predict a group velocity reduction as well as strong fluctuations of the corresponding group index in the range 1.1