We demonstrate a broadband light absorber with its absorption being able to reach as high as 90 % and above ranging from the ultraviolet to the visible regimes. A theoretical model is given for the purpose of analyzing the physical mechanism of the absorption. By applying the equivalent T circuit model of metamaterial layers to the analysis of our designed absorber, our calculated results are in good agreement to that of the theoretical model and satisfy the perfectabsorption condition very well.

The influence of an ultrathin GaP (or GaAs) sublayer on the nonradiative intraband relaxation in InAs/InGaAsP/InP quantum dots (QDs) is investigated. It is found that, based on our studies, the QDs with some heights (e.g., 1.5 nm) and GaP sublayer thicknesses (e.g., 1.03 monolayers) present the first excited state (ES) with higher state degeneracy with respect to ground state (GS), which suggests that the Auger relaxation is triggered more easily. We also find that the energy difference of the ES and GS decreases with increasing sublayer thickness, which suggests that the electron–phonon interaction is affected. This work further presents a study of intraband relaxation for an InAs/InP QD with a GaP or GaAs sublayer. It is found that there is a critical thickness of the GaP sublayer: When the sublayer is less than the critical thickness, the intraband relaxation is only determined by one-longitudinal optical (LO) phonon or two-LO phonons, which is dependent on QD heights. However, with the GaAs sublayer, QDs do not have the above feature. This finding may be helpful for designing and optimizing high-speed QD devices.

Inspired by imaging principle of near-field scanning optical microscope (NSOM), meta-pillars array is designed and analyzed on the basis of microscopic imaging application with high resolution. Finely focused spots acting as tiny secondary sources for illumination at near-field can be derived under supporting of the meta-pillars for the purpose of increasing imaging resolution. Numerical calculation is carried out on the basis of finite difference and time domain (FDTD) algorithm. Our calculation results demonstrate that the meta-pillars are capable of supporting the microscopic imaging at sub-wavelength resolution.

We report a perfect metasurface structure-based optical absorber consisting of a tri-layer metaldielectric-metal system in ultraviolet band. Optical power absorption of over 91% has been observed in entire ultraviolet band, and can even reach to the level of as high as 99% in a certain local near waveband. Unique properties of the perfect absorption are independent on polarization state of the incoming light, and insensitive to variation of structural dimension. We discuss the effect of geometrical parameters of the structure such as height and radius on the basis of theoretical calculation results. In addition, the influence of materials upon performance of the absorber is presented. The efficient light absorption can be attributed to plasmonic resonance.

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