Wideband Omnidirectional Polarization‐Insensitive Light Absorbers Made with 1D Silicon Gratings

Photonic resonance in lossy films with 1D periodicity is generally associated with narrow spectral, angular, and polarization‐selective absorption. Contrarily, in this paper a 1D amorphous Si grating structure is demonstrated that efficiently absorbs fully hemispherical unpolarized light in the entire visible spectral domain. The absorber provides a broad spectral continuum of densely populated resonant photonic states as well as a cooperating wide‐angular antireflection effect, resulting in the observed broadband, omnidirectional, and polarization‐insensitive light absorption. The absorber performance is experimentally verified with precise fabrication and conical input beam spectral analysis. The absorber's fundamental mechanisms, explained in detail, are applicable to other semiconducting materials including GaAs, Ge, and SiC. These materials provide the absorber design with potential impact on practical device applications including near/mid/long infrared detectors and stray background rejection surfaces for imaging and spectroscopy.