Ultra-large near-infrared omnidirectional photonic bandgaps in cascaded one-dimensional photonic crystals containing all-dielectric metamaterials.

In conventional one-dimensional (1-D) photonic crystals (PCs) consisting of isotropic dielectrics, photonic bandgaps (PBGs) substantially shift toward shorter wavelengths as incident angle increases. This strong blueshift characteristic of PBGs significantly reduces the widths of near-infrared omnidirectional photonic bandgaps (OPBGs). Recently, researchers achieved a kind of special PBG called angle-insensitive PBGs in 1-D PCs containing all-dielectric elliptical metamaterials (EMMs). The emergence of angle-insensitive PBGs provides us a possibility to achieve ultra-large near-infrared OPBGs. Herein, we design two 1-D PCs containing all-dielectric EMMs with near-infrared angle-insensitive PBGs in different wavelength ranges. By cascading two 1-D PCs containing all-dielectric EMMs together, we achieve an ultra-large near-infrared OPBG with a width up to 1.004 µm (relative bandwidth of 63.9%). In addition, the width of the near-infrared OPBG demonstrates robustness against the layer thickness. Our work not only provides a feasible route to achieving ultra-large near-infrared OPBGs, but also facilitates the design of broadband omnidirectional mirrors.