Achieving the broadband response of metamaterial absorbers has been quite challenging due to the inherent bandwidth limitations. Herein, the investigation was made of a unique kind of visible light metamaterial absorber comprising elliptical rings-shaped fractal metasurface using tungsten metal. It was found that the proposed absorber exhibits average absorption of over 90% in the visible wavelength span of 400–750 nm. The features of perfect absorption could be observed because of the localized surface plasmon resonance that causes impedance matching. Moreover, in the context of optoelectronic applications, the absorber yields absorbance up to ~ 70% even with the incidence obliquity in the range of 0°–60° for transverse electric polarization. The theory of multiple reflections was employed to further verify the performance of the absorber. The obtained theoretical results were found to be in close agreement with the simulation results. In order to optimize the results, the performance was analyzed in terms of the figure of merit and operating bandwidth. Significant amount of absorption in the entire visible span, wide-angle stability, and utilization of low-cost metal make the proposed absorber suitable in varieties of photonics applications, in particular photovoltaics, thermal emitters and sensors.

The spectral characteristics of nanostructured hyperbolic metamaterial (HMM)-based absorber is investigated. The HMM structure is comprised of periodically arranged assembly of gold nanostrips. The results indicate nearly perfect absorption by the structure in the entire ultraviolet (UV) regime of the electromagnetic spectrum under certain configuration - the feature which would be useful for UV-shield related applications. The absorptivity of the structure can be tailored by altering the slant angle and thickness of gold nanostrips (in the HMM structure). The effect of altering the incidence angle of light is also reported.

A specially designed metallic E-shaped fractal-based perfect metamaterial absorber (PMA) with fairly wideband absorptivity in the K- and Ka-bands of the microwave regime was investigated. The PMA top surface is comprised of square-shaped split-ring resonators (SRRs) surrounded with the stated fractal design. The absorptivity of PMA was analyzed in the range of 20 – 30 GHz for the normal and oblique incidence of waves. Both the transverse electric (TE) and transverse magnetic (TM) modes were taken up to observe the robustness of the proposed design. It was observed that the fractal resonators exhibit capacitive effect at low frequencies, whereas the SRRs manifest capacitive effect at higher frequencies. The simulation and measured results were found to be in fairly good agreement. It is expected that the proposed design of PMA would be useful for 5G communication applications.

A specially designed tunable hyperbolic metamaterial (HMM) based on plasmon induced transparency (PIT) of fractal in the near-infrared (NIR) regime was proposed. The HMM-layer constitutes the top metasurface, which is comprised of fractal-like nanospheres of silver (Ag) metal. A bilayer of graphene is sandwiched between the top HMM and bottom silicon (Si) substrate. The permittivity of graphene bilayer was deduced corresponding to different chemical potentials (of graphene). PIT of the proposed structure was obtained in the 3000-4000 nm wavelength band by employing the finite difference time domain simulation under the excitation of a fundamental transverse magnetic (TM) mode. The effects of incidence angle and graphene chemical potential on the transmission characteristics were investigated. Furthermore, the PIT windows could be tuned by altering the radii of Ag nanospheres in the HMM layer and chemical potential of bilayer graphene. Such systems would be useful in varieties of applications, e.g., switching, energy harvesting, sensing in environmental, and/or medical diagnostics, particularly in detecting the existing impurities in human blood and urine.

A hyperbolic metamaterial (HMM)-based absorber, comprised of metasurface having periodically arranged titanium (Ti) nanospheres, was investigated. The wavelength-dependent permittivity of metasurface and absorptivity of structure were evaluated considering different volume fractions of Ti metal. Also, both the transverse electric (TE) and transverse magnetic (TM) incidence polarizations were considered along with different values of the incidence angle. Using the finite difference time domain (FDTD) simulation technique, the absorber was found to exhibit high absorption in the visible and near-infrared regimes of electromagnetic spectrum. With such features, the proposed HMM structure has prospects in the development of plasmonic devices capable to enhance the solar cell efficiency, solar heater, and other optical technology-oriented needs.