Spatially and Spectrally Resolved Narrowband Optical Absorber Based on 2D Grating Nanostructures on Metallic Films

Abstract

Two spatially and spectrally resolved narrowband absorbers based on 2D grating nanostructures (polymethylmethacrylate (PMMA) grating and gold grating) on metallic films are designed, fabricated, and characterized. For PMMA grating on a metallic film, the measured absorption bandwidth is 12 nm with a nearly 80% absorption at normal incidence. The transverse electric (TE) localized mode shows a calculated 3.5° angular width. The transverse magnetic (TM) resonant mode supports both a localized mode and a lattice mode. The TM lattice mode shows a calculated angular width of 0.75° and exhibits a large wavelength‐angle sensitivity of nearly 15 nm per degree and a large absorption‐angle sensitivity of 77.5% per degree. For gold grating on a metallic film, the measured absorption bandwidth is 40 nm with a nearly 70% absorption. Such spatially and spectrally resolved 2D nanostructure arrays with large angle sensitivities have potential applications in angle measurement, thermal emitters, optical filters, and biosensors.