Ultra-broadband absorber based on photonic topological transition with large-ε′ metals

We propose and experimentally demonstrate an ultra-broadband metamaterial absorber based on photonic topological transition by using metals with large real part of permittivity (ε′). The simulation results show that the absorptivity is larger than 0.9 in the wavelength range from 400 nm to 2832 nm. The simulation results also show that the absorption effect is insensitive to the incident angle and polarization. According to the effective medium theory, the ultra-broad bandwidth is originated from the photonic topological transition. In addition, the analyses reveal that the absorption bandwidths can be extended by manipulating the wavelengths of photonic topological transition (PTT) points with large-ε′ metals. Furthermore, an ultra-broadband metamaterial absorber with multilayer films is fabricated by using standard film deposition techniques. The measured results show that the absorptivity is larger than 0.9 under normal incidence over the measured wavelength range of 400–2500 nm. This metamaterial absorber is expected to be potential candidate for various applications, such as thermal photovoltaic energy conversion, detectors, and solar cells.