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High performance and cost-effective solar absorbers are crucial for various optical applications, such as solar collection and thermophotovoltaic devices. This study designs and experimentally demonstrates a wide-angle and broadband solar absorber. The proposed absorber is composed of tapered polyimide substrate and Al-Cr-SiO2-Cr-SiO2 thin-film based on the optical interference of the multilayer thin film and excited magnetic resonance of light-trapping structures. The composite process of the colloidal lithography method and magnetron sputtering is employed for efficient fabrication in a large area. The average absorbance is more than 93% from 300 nm to 2500 nm and shows an angular tolerance of up to 60°. The high efficiency and large-area fabrication capability demonstrated by the proposed solar absorber presents future application potential in flexible solar collection devices.

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An optical Fano resonance, which is caused by birefringence control rather than frequency selection, is discovered. Such birefringence-induced Fano resonance comes with fast-switching radiation.The resonance condition ε t < 1/ε r is revealed and a tiny perturbation in birefringence is found to result in a giant switch in the principal light pole induced near surface plasmon resonance. The loss and size effects upon the Fano resonance have been studied Fano resonance is still pronounced, even if the loss and size of the object increase. The evolutions of the radiation patterns and energy singularities illustrate clearly the sensitive dependence of Fano resonance upon the birefringence.

A proposal of Fano lasing spaser is demonstrated in a superlattice meta-grating, in which the spatial-temporal lasing dynamics is investigated by a semiclassical model that involves the coupling between full-wave electromagnetic equations and electronic rate equations. The out-of-phase dark mode and in-phase bright mode supported by the meta-grating can be independently tailored by the width of the thin strip and the fat strip in each supercell of the meta-grating. It provides a facile way to alter the dark/bright mode to overlap the emission/absorption window of a given four-energy-level gain medium simultaneously, in which case the system exhibits the optimal lasing characteristic. Our findings may provide a useful guideline to design low-threshold and high-efficient miniaturized lasers.