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Refractory materials have wide applications due to their high thermal and chemical stability. In this work, we numerically design the plasmonic structure for perfect light absorption using the resonant behaviours for these materials. The results of the simulation are presented using the three-dimensional finite-difference time-domain method. The maximum absorption reaches 99.9% and the near-unity absorption window spans a bandwidth of 1182 nm from 413 nm in the visible to 1595 nm in the near-infrared range. Strong plasmonic near-field coupling between the adjacent parts in the split circular Ti resonator and their coupling to the plasmon resonances of the TiN layer are the main reasons for the ultra-broadband perfect absorption. Moreover, the absorption is observed to be incident angle insensitive and polarization independent. Absorption properties can be manipulated via tuning the structural parameters. These impressive absorption features and the high thermal stability can have wide applications in the high-intensity or extreme condition operation such as laser pumping and nonlinear optics, and solar related technologies including thermal steam generation and desalination of seawater. [ABSTRACT FROM AUTHOR]

Achieving perfect electromagnetic wave absorption with a sub-nanometer bandwidth is challenging, which, however, is desired for high-performance refractive-index sensing. In this work, we theoretically study metasurfaces for sensing applications based on an ultra-narrow band perfect absorption in the infrared region, whose full width at half maximum (FWHM) is only 1.74 nm. The studied metasurfaces are composed of a periodic array of cross-shaped holes in a silver substrate. The ultra-narrow band perfect absorption is related to a hybrid mode, whose physical mechanism is revealed by using a coupling model of two oscillators. The hybrid mode results from the strong coupling between the magnetic resonances in individual cross-shaped holes and the surface plasmon polaritons on the top surface of the silver substrate. Two conventional parameters, sensitivity (S) and figure of merit (FOM), are used to estimate the sensing performance, which are 1317 nm/RIU and 756, respectively. Such high-performance parameters suggest great potential for the application of label-free biosensing. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a novel perfect absorber platform by combining the colloidal crystal and refractory metal layer. Dual-band absorption with the efficiency up to 99.8% (0. 336 μ m) and 99.1% (1. 382 μ m) is achieved. Moreover, the absorption bandwidths are 81 nm and 1237 nm for the two bands in the UV and near-infrared ranges, suggesting the simultaneous achievement of narrowband and ultra-broadband absorption. Furthermore, the resonant wavelengths in the two bands are with the geometric multiples up to 3 ∼ 6, indicating the large differential frequency responses. In addition, the absorption properties can be artificially adjusted via the structural parameters. These features can hold potential applications in the nonlinear optics such as frequency multiplication, difference and mixing, and the selective spectral filtering and manipulation, etc. • A novel absorber is achieved by combining colloidal crystal and refractory metal. • Dual-band absorption with A of 99.8% and 99.1% is achieved. • Narrowband and ultra-broadband absorption is simultaneous achieved. • It can hold applications in nonlinear optics, selective filtering, etc. [ABSTRACT FROM AUTHOR]

Electrically modulating and switching the light absorption properties of monolayer graphene in near-infrared region has potentials in optoelectronic devices (e.g., photodetectors) and optical communication systems (e.g., modulators). In this work, we demonstrate numerically a broadband near-infrared absorption enhancement of monolayer graphene, due to the magnetic dipole resonance in metamaterials. The broadband light absorption in monolayer graphene can be largely modulated to realize an electrically switchable effect, via bias voltage for the interband transition of graphene to be near the magnetic dipole resonance. The absorption modulation depth is able to vary quickly from almost zero to nearly 100% in a very narrow wavelength range around the interband transition. Electrically modulating and switching the light absorption properties of monolayer graphene in near-infrared region has potentials in optoelectronic devices (e.g., photodetectors) and optical communication systems (e.g., modulators). In this work, we firstly demonstrate numerically a broadband near-infrared absorption enhancement of monolayer graphene, due to the magnetic dipole resonance in metamaterials. Then, we show that the broadband light absorption in monolayer graphene can be largely modulated to realize an electrically switchable effect, via bias voltage for the interband transition of graphene to be near the magnetic dipole resonance. The absorption modulation depth is able to vary quickly from almost zero to nearly 100% in a very narrow wavelength range around the interband transition. Image 107 [ABSTRACT FROM AUTHOR]

Narrowband light absorbers are of great importance in many practical applications, such as color filtering and thermal emission. Here, we experimentally demonstrate a multispectral narrowband light absorber based on a silicon nano-cavity coupled metallo-dielectric cavity. Seven absorption bands with excellent absorption features are achieved in the near-infrared region. Theoretical results indicate that the multi-band light absorption strongly attributes to the hybridization coupling between the optical modes of the silicon cavity and the plasmonic resonances of the metallic structure. These optical features hold the absorber with wide applications in optoelectronics. • A novel narrowband light absorber is demonstrated in a silicon nano-cavity coupled metallo-dielectric structure. • The maximal absorbance above 94% and bandwidth less than 21 nm are achieved. • Ultra-narrow bandwidth down to single-digit level (4 nm) is achieved in the calculation. • This absorber can be fabricated in large-area at low-cost by the standard technique. [ABSTRACT FROM AUTHOR]

Perfect absorption of electromagnetic wave is emerging as a promising technology for its potential applications in harvesting solar energy, infrared detection and photovoltaic devices. Recent studies have reported a variety of plasmonic or meta-material structures, which are designed and fabricated to provide broadband absorption by utilizing multiple resonators in a composite unit cell. Coupled plasmonic-photonic micro-cavities, formed by using the colloidal crystal that does not have closed packed structure as the structural template, are surprisingly found to be efficient infrared absorption devices in an ultra-broadband frequency range. Taking the absorptivity above 0.9 into account, the operation bandwidth is up to 2.851 μm in the infrared range. The excellent absorption capability can be attributed to the cooperation effects of the plasmonic resonances by the metal caps and the photonic modes by the colloids. The absorber exhibits polarization-independent and wide-angle behaviors. These findings not only reveal the advantages of colloidal crystals as low-cost materials for ultra-broadband absorbers, but also provide inspiration for future development of high-performance, large-area infrared optoelectronic devices. [ABSTRACT FROM AUTHOR]