Benefited from the well‐known Mie resonance, a plethora of physical phenomena and applications are attracting attention in current research on dielectric‐based nanophotonics. High‐index dielectric metastructures are favorable to enhance light‐matter interaction in nanoscale with advantages such as low loss, optical magnetism, and multipolar responses, which are superior to their plasmonic counterpart. In this review, we highlight the important role played by Mie resonance‐based multipolar and multimodal interaction in nanophotonics, introducing the concept of “multipole and multimode engineering” in artificially engineered dielectric‐based metastructures and providing an overview of the recent progress of this fast‐developing area. The scope of multipole and multimode engineering is restricted not only in multipolar interferences of meta‐atom and meta‐molecule but also in the nontrivial intermodal coupling (Fano resonance and bound states in the continuum), in the collective mode and the surface lattice mode appearing via periodic meta‐lattices and aperiodic meta‐assembly, in chiral enhancement via chiral and achiral dielectric metastructures, and in Mie resonance‐mediated hybrid structures (Mie‐plasmon and Mie‐exciton). Detailed examples and the underlying physics of this area are discussed in‐depth, in order to lead the multifunctional metastructures for novel applications in the future.

The absorbance of a free-standing ultrathin layer is limited to 50%; we overcome this limitation by numerically investigating a wavelength-selective perfect absorber based on Mie resonance and degenerate critical coupling. We extend the wavelength of close-to-unity absorbance to the entire visible region by controlling the radiative loss and intrinsic loss. Radiative loss can be controlled by embedding the Mie resonator into a thin film with the defined refractive index. Meanwhile, intrinsic loss can be controlled by addition of a dielectric cap with a higher extinction coefficient on the Mie resonator. Such all-dielectric perfect absorbers can be applied to efficient photodetectors, imaging sensor pixels, or all-optical switching devices mediated by the photothermal effect.

The burgeoning of artificial intelligence has brought great convenience to people’s lives as large-scale computational models have emerged. Artificial intelligence-related applications, such as autonomous driving, medical diagnosis, and speech recognition, have experienced remarkable progress in recent years; however, such systems require vast amounts of data for accurate inference and reliable performance, presenting challenges in both speed and power consumption. Neuromorphic computing based on photonic integrated circuits (PICs) is currently a subject of interest to achieve high-speed, energy-efficient, and low-latency data processing to alleviate some of these challenges. Herein, we present an overview of the current photonic platforms available, the materials which have the potential to be integrated with PICs to achieve further performance, and recent progress in hybrid devices for neuromorphic computing.

In principle, the absorbance of a free-standing ultra-thin film is limited to 50%. To overcome this limitation, an all-dielectric perfect absorber is proposed herein based on the concept of degenerate critical coupling (DCC) of quadrupole modes. We study the absorbance of a dielectric elliptic cylinder and find that perfect absorption can be achieved by spectrally overlapping peaks of electric and magnetic quadrupole modes. This suggests that the DCC method can be extended to the quadrupole modes beyond dipole modes. Such an all-dielectric perfect absorber can be used in photodetectors, optical filters, and optical modulators mediated by the photothermal effect.

In this paper, we theoretically and experimentally demonstrated photothermal nonlinearities of both forward and backward scattering intensities from quasi‐perfect absorbing silicon‐based metasurface with only λ /7 thickness. The metasurface is efficiently heated up by photothermal effect under laser irradiation, which in turn modulates the scattering spectra via thermo‐optical effect. Under a few milliwatt continuous‐wave excitation at the resonance wavelength of the metasurface, backward scattering cross‐section doubles, and forward scattering cross‐section reduces to half. Our study opens up the all‐optical dynamical control of the scattering directionality, which would be applicable to silicon photonic devices.

Silicon metasurfaces have been attracting interest in the sensing field because of their ability to support magnetic Mie resonance, low optical heating, and CMOS-compatible fabrication processes. Herein, we demonstrate that the sensitivity of the magnetic dipole (MD) mode for nanodisk Mie resonators (as high as 385 nm/RIU) is similar to the sensitivity of plasmonic metasurfaces and greater than that of the electric dipole (ED) mode of nanodisk Mie resonators. We also engineer the thickness of Mie resonators to achieve an MD-mode linewidth as small as 0.56 nm and a figure of merit greater than 160 RIU⁻¹. The measured sensitivity of the MD mode is more accurate than that of the ED mode, which is more prone than the MD mode to measurement errors arising from the partial filling of the liquid. Our study paves the way for the development of MD-mode-based dielectric biosensors for use in personal healthcare and medical diagnosis.