Fast And Slow Light In Artificial Composite Materials

Light with the group velocity faster than the one in a vacuum is defined as fast light. On contrast, it is slow light. By suitably choosing the parameters of the system, we could control the transmission of the pulse. Practical application such as optical filters, optical delay lines, optical data storage and devices for quantum information will be realized when we could effectively control the velocity of the pulse.We focus our attention on the transmitted properties and velocities of the pluses propagating in non-spherical composites and periodic/quasi-periodic structures. Our main work is listed as follows,1. The effect of the shape and compositional gradation of particles on the group velocity of two-phase compositesEffective medium approximation is derived to estimate the effective refractive index and the group velocity in two-phase composites. Enhanced group velocity may be achieved through the suitable adjustment of the particles' shape and shape distribution. The range of the volume fractions, in which the group velocity is enhanced, will expand, once we take into account the inclusion's shape and shape distribution. When the pulse's incident angle is large, both the particles' shape and the graded structure reduce the group velocity in the graded composites. The effect of graded structure on reducing the group velocity becomes more significant for larger incident angle.2. Subluminal and superluminal pulse propagation in inhomogeneous media of non-spherical particlesTo account for the shape effect, we adopt Maxwell-Garnett type approximation to obtain the effective dielectric function of composites. Based on the group index, transmitted time and pulse shape, we find that the particles' shape (characterized by the depolarization factor) plays an important role in determining the subluminal and superluminal pulse propagations through the system. When the inclusions' shape is not spherical, it is possible to observe significant superluminal behavior of the pulse...