A tunable wide-angle narrowband perfect absorber based on an optical cavity containing hyperbolic metamaterials.

We demonstrate that wide-angle narrowband absorption can be achieved from a microcavity where a hyperbolic metamaterial and a dielectric layer are sandwiched between two metal reflectors. As the incident angle changes, the phase-shift variation in the hyperbolic metamaterial can compensate that in the dielectric layer and, consequently, result in the angle-insensitive Fabry-Perot resonance in the proposed cavity. Silicon, indium tin oxide (ITO), and gold layers are used to construct the microcavity to produce a narrow absorption band in the near-infrared region. Our device exhibits good absorption stability over a wide angle range of incidence from 0° to 70°. Moreover, the absorption wavelength can be tuned by changing the thickness of the resonator. The presented absorber may find potential applications in the design of narrowband thermophotovoltaic emitters, sensitive detectors, filters,