Enhanced group velocity in composite media of particles with non-spherical shape or shape distribution

Effective medium approximation is derived to estimate the effective refractive index n(e) and the group velocity nu(g) in two-phase composites in which one of the components is non-spherical, and even distributed in shape. 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 non-spherical shape or the shape distribution. Therefore, the non-spherical shape and shape distribution play crucial roles in determining the group velocity in two-phase composites.