Effect of refractive index of environment medium on electromagnetic mode density in photonic band gaps

The purpose of this work is to analyze the effect of the environmental medium on the density of mode (DOM) in a 1-D photonic crystal. The results show that for a symmetric environment, the DOM changes non-monotonously with an increase in the refractive index of the environment medium, while for an asymmetric environment, the DOM increases monotonously with an increase of the refractive index of the substrate. It is found that low DOM at midgap and high DOM at the band edge can be achieved simultaneously only when a photonic crystal works in an environment where the input medium and the substrate have the same refractive indices. The effect of the refractive index on the surrounding material on the band edge laser is also discussed.