Rongyang Xu 교수

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 los

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 mode

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 o

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 Mi

Graphene is a two-dimensional material with great potential for photodetection and light modulation applications owing to its high charge mobility. However, the light absorption of graphene in the near-infrared range is only 2.3%, limiting the sensitivity of graphene-based devices. In this study, we propose a graphene perfect absorber based on degenerate critical coupling comprising monolayer graphene and a hollow silicon Mie resonator array. In particular, monolayer graphene achieves perfect ab

Perfect absorbers based on all-dielectric metasurfaces exhibit great potential in photodetection, photovoltaics, and imaging applications. This study proposes and demonstrates an all-dielectric broadband absorber comprising subwavelength-thick nanopillar Mie resonators in the visible light range. This nanopillar functions as a perfect absorber based on degenerate critical coupling with a characteristic "degenerate critical length." At this length, the nanopillars are capable of achieving perfect

We design a wideband all-dielectric perfect absorber of nanopillar Mie resonators based on degenerate critical coupling. In addition, the nanopillar perfect absorber is found to have a characteristic “degenerate critical length” beyond which the absorption peak is almost unaffected by increasing length. Based on the existence of the degenerate critical length, we develop a broadband dielectric quasi-perfect absorber by stacking nanopillar Mie resonators of different materials that selectively ab

An on-chip asymmetric directional coupler (DC) can convert fundamental modes to higher-order modes and is one of the core components of mode-division multiplexing (MDM) technology. In this study, we propose that waveguides of the asymmetric DC can be trimmed by silicon ion implantation to tune the effective refractive index and facilitate mode conversion into higher-order modes. Through this method of tuning, transmission changes of up to 18 dB have been realized with one ion implantation step.

Fano resonances are observed in a composite metamaterial that consists of an electric split ring resonator eSRR and an I-shaped resonator ISR. By adjusting the length of the ISR the degree of asymmetry in the line shape of the composite metamaterial can be controlled and even made to be symmetric. In contrast to other methods to create Fano resonances, the individual modes of the eSRR and ISR have the same symmetry and are not evanescently coupled to each other. The transmission is simulated usi

Abstract We propose a refractometric sensor based on hollow silicon Mie resonators of a toroidal magnetic dipole mode. This mode has a pair of antiparallel electric dipoles perpendicular to the silica substrate; thus, the radiation of the mode is suppressed, resulting in an ultra-narrow reflection peak linewidth of 0.35 nm. In addition, the hollow structure enhances the interaction between the enhanced electric field and the surrounding medium, thus improving the sensitivity. The proposed Mie re

Abstract Metasurfaces have attracted widespread interest owing to their ability to control light at the nanoscale level. However, the optical response of dipole mode-based metasurfaces is sensitive to changes in the resonator period and the light incidence angle; thus, the device performance typically degrades in practical applications owing to the presence of non-normal incident light. Here, we study cross-shaped Mie resonators based on quadrupole modes, whose optical response is almost indepen

By leveraging the high propagation speed and inherent parallelism of light, hardware accelerators based on photonic integrated circuits enable high‐speed, low‐power computing, positioning them as promising solutions to meet the rapidly increasing computational demands driven by advancements in artificial intelligence (AI). Within photonic accelerators directional couplers are crucial components for splitting and combining light, facilitating parallel computation and addition operations. However,

To overcome the absorption limit of an ultra-thin layer, all-dielectric perfect absorbers of dipole modes can be realized based on degenerate critical coupling. Here, we propose theoretically a cross-shaped silicon perfect absorber of quadrupole modes in the visible region and demonstrate that the degenerate critical coupling applies to higher-order modes.

The absorption of a free-standing ultra-thin film supporting a single resonant mode is, in principle, limited to 50%. Based on the degenerate critical coupling (DCC) of dipole modes, silicon Mie resonators can overcome the absorption limit and achieve perfect absorption in the green light range. DCC requires that the radiative loss of each dipole mode matches material loss. Due to the material properties of silicon, the material loss varies with wavelength. Therefore, flexible tuning of radiativ