Wide-Angle Absorption Based on Angle-Insensitive Light Slowing Effect in Photonic Crystal Containing Hyperbolic Metamaterials

Light-slowing effect at band edges in photonic crystals (PCs) is widely utilized to enhance optical absorption. However, according to the Bragg scattering theory, photonic bandgaps (PBGs) in traditional all-dielectric one-dimensional (1-D) PCs shift towards shorter wavelengths as the incident angle increases. Therefore, light-slowing effect in traditional all-dielectric 1-D PCs is also angle-sensitive. Such angle-sensitive property of light-slowing effect in traditional all-dielectric 1-D PCs poses a great challenge to achieve wide-angle absorption. In this paper, we design an angle-insensitive PBG in a 1-D PC containing hyperbolic metamaterials based on the phase-variation compensation theory. Assisted by the angle-insensitive light-slowing effect at the angle-insensitive band edge, we achieve wide-angle absorption at near-infrared wavelengths. The absorptance keeps higher than 0.9 in a wide angle range from 0 to 45.5 degrees. Besides, the wide-angle absorption is robust when the phase-variation compensation condition is slightly broken. Our work not only provides a viable route to realize angle-insensitive light slowing and wide-angle light absorption, but also promotes the development of light-slowing- and absorption-based optical/optoelectronic devices.