Conceptual Design of Omnidirectional Bandgap in 1D Photonic Crystals Using Various Refractive Index Profiles

Herein, the theoretical engineering of omnidirectional bandgap in a 1D photonic crystal using different refractive index profiles is reported. The periodicity of each profile is maintained unchanged. However, the refractive index modulation is presumed to vary either discretely or continuously. Bragg stacks demonstrate the discrete refractive index modulation, whereas sinusoidal and sawtooth patterns are employed to generate the continuous modulation of refractive index. The corresponding omnidirectional bandgap is evaluated as a function of the optical thickness, the limiting values of the refractive index profiles, and the nature of the modulation profile using the transfer matrix approach. At high refractive index contrast, a large bandgap is achieved employing a sinusoidal shape. However, the bandgap associated with the Bragg profile widens as refractive index contrast decreases. This study reveals that the shape of the refractive index profile is a significant parameter that can drastically tune the omnidirectional bandgap of the photonic crystal.