We show that weakly dissipating dielectric spheres made of materials such as glass, quartz, etc. can support high order Fano resonances associated with internal Mie modes. These resonances, happening for specific values of the size parameter, yield field-intensity enhancement factors on the order of 104–107, which can be directly obtained from analytical calculations. Associated to these “super-resonances”, we analyze the emergence of magnetic nanojets with giant magnetic fields, which might be attractive for many photonic applications.

It is well known that electromagnetic radiation propagates along a straight line, but this common sense was broken by the artificial curved light-the Airy beam. In this Letter, we demonstrate a new type of curved light beam besides the Airy beam, the so-called "photonic hook." This photonic hook is a curved high-intensity focus by a dielectric trapezoid particle illuminated by a plane wave. The difference between the phase velocity and the interference of the waves inside the particle causes the phenomenon of focus bending.

In this letter, we reported the experimental observation of a photonic hook (PH)—a type of near-field curved light generated at the output of a dielectric cuboid, featuring a broken symmetry and dimensions comparable to the electromagnetic (EM) wavelength. Given that the specific value of the wavelength is not critical once the mesoscale conditions for the particle are met, we verified these predictions experimentally using a 0.25 THz continuous-wave source. The radius of curvature associated with the PH-generated is smaller than the wavelength, while its minimum beam-waist is about 0.44λ. This represents the smallest radius of curvature ever recorded for any EM beam. The observed phenomenon is of potential interest in optics and photonics, particularly, in super-resolution microscopy, manipulation of particles and liquids, photolithography, and material processing. Finally, it has a universal character and should be inherent to acoustic and surface waves, electrons, neutrons, protons, and other beams interacting with asymmetric mesoscale obstacles.

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Achieving high open-circuit voltage and high short-circuit current density simultaneously is a big challenge in the development of highly efficient perovskite solar cells, due to the complex excitonic nature of hybrid organic-inorganic semiconductors. Herein, we developed a facile and effective method to fabricate efficient plasmonic PSC devices. The solar cells were prepared by incorporating Au nanoparticles (NPs) into mesoporous TiO films and depositing a MgO passivation film on the Au NP-modified mesoporous titania via wet spinning and pyrolysis of magnesium salt. The PSCs obtained by combining Au NPs and MgO demonstrated a high power conversion efficiency of 16.1%, with both a high open-circuit voltage of 1.09 V and a high short-circuit current density of 21.76 mA cm. The device achieved a 34.2% improvement in the power conversion efficiency compared with a device based on pure TiO. Moreover, a significant improvement of the UV stability in the perovskite solar cell was achieved due to the combined use of Au NPs and insulating MgO. The fundamental optics and physics behind the regulation of energy flow in the perovskite solar cell and the concept of using Au NPs and MgO to improve the device performance were explored. The results indicate that the combined use of Au NPs and a MgO passivation film is an effective way to design high performance and high stability organic-inorganic perovskite photovoltaic materials.