Eliminating excess phase accumulation in a continuous perturbed heterogeneous planar PhC

In this paper, we propose an asymmetric distribution of a hexagonal lattice for achieving near-zero group velocity with negative group delay. This study reports the effect of the continuous geometric perturbation on the photonic band diagram and consequently its impact on phase velocity, group velocity, and effective refractive index. We provide a promising method for modifying the photonic band diagram for obtaining an exotic dispersion diagram. With this obtaining a broadband spanning from E to L band that envelop of light pulse traverse with almost zero velocity is promising enough to apply it in a wide variety of light-based devices.