arXiv subjects

Yongkang Dong

Publications and source records attributed to Yongkang Dong.

5 recordsLinked to original sources

arXiv2026

Enhanced chiral response of hybrid photonic structures empowered by Mie resonances

Chiroptical response provides a powerful route to control light-matter interactions through light handedness, with crucial importance in polarization control, chiral sensing, and nonlinear photonics. Hybrid structures may offer a novel route to engineer such responses by coupling plasmonic field localization with dielectric Mie resonances within a single nanostructure. However, in chiral metasurfaces, hybridization has largely been treated as a means of resonance enhancement, while its role in actively reshaping and reversing intrinsic plasmonic chirality remains largely unexplored. Here, we demonstrate a hybrid metasurface in which a dielectric Mie resonance mediates enhanced chiral response of plasmonic building blocks. By coupling a Si nanocylinder to trapezoidal Au nanobars, a weak and mode-selective plasmonic chiral seed is reorganised into two opposite-handed hybrid resonances, producing near-unity circular dichroism with spectral sign flipping. Extending this mechanism to nonlinear regime, the same hybrid-mode selectivity produces strongly nonlinear chiral emission and near-unity third-harmonic generation circular dichroism of either sign. We believe these results establish plasmonic-Mie hybridization as a novel mechanism for engineering high-purity, sign-switchable linear and nonlinear chirality in compact metadevices.

physics.optics↗

arXiv2026

Artificial Anisotropy Induced Bound States in the Continuum for Integrated Photonic Waveguide

Bound states in the continuum (BICs) enable counterintuitive light confinement without radiation loss, providing a powerful foundation for integrated photonic waveguides. However, existing BIC waveguides are predominantly realized through geometry-dependent designs, where the BIC condition is restricted to narrowly defined structural parameters, limiting design flexibility and practical applicability. Artificial optical anisotropy is introduced as a new design paradigm for BIC waveguides. Implemented using subwavelength-grating (SWG) metamaterials, continuously tailorable anisotropy provides an independent degree of freedom for deterministically reshaping the radiative continuum, enabling flexible formation and systematic control of BIC waveguides over a broad design space. Anisotropy-engineered symmetry breaking further enables controllable asymmetric radiation and precisely tailored field leakage. This paradigm transforms BIC waveguides from geometry-constrained structures into an anisotropy-engineered platform, establishing a general framework for programmable radiation engineering and next-generation integrated photonic devices.

physics.optics↗

arXiv2025

Dispersion-Engineered Compact Twisted Metasurfaces Enabling 3D Frequency-Reconfigurable Holography

Flexible dispersion manipulation is critical for holography to achieve broadband imaging or frequency division multiplexing. Within this context, metasurface-based holography offers advanced dispersion control, yet dynamic reconfigurability remains largely unexplored. This work develops a dispersion-engineered inverse design framework that enables 3D frequency-reconfigurable holography through a twisted metasurface system. The physical implementation is based on a compact layered configuration that cascades the broadband radiation-type metasurface (RA-M) and phase-only metasurface (P-M). The RA-M provides a phase-adjustable input to excite P-M, while the rotation of P-M creates a reconfigurable response of holograms. By employing the proposed scheme, dynamic switching of frequency-space multiplexing and achromatic holograms are designed and experimentally demonstrated in the microwave region. This method advances flexible dispersion engineering for metasurface-based holography, and the compact system holds significant potential for applications in ultra-broadband imaging, high-capacity optical display, and switchable meta-devices.

physics.optics↗

arXiv2025

High Numerical Aperture Achromatic Meta-Devices through Dispersion Compensation

Dispersion engineering is a long-standing challenge in optical systems, and it is particularly important for metasurfaces, which naturally suffer from strong chromatic aberrations due to their ultralow profile. Stacks of metasurfaces have recently implemented dispersion control to address these challenges. However, these approaches still suffer from bottlenecks in terms of the available material refractive index and required aspect ratios, resulting in limited phase and group delay coverage, constraining their numerical aperture (NA), size and operating bandwidth. To address these challenges, we explore a dispersion compensation strategy combined with full-wave simulation-free inverse design to implement ultra-high NA, broadband dispersion control in metasurfaces, not requiring large refractive index materials and high aspect ratio processing technology. We experimentally demonstrate multiple meta-devices with highly customized dispersion engineering in the microwave regime, including broadband achromatic diffraction-limited meta-devices with NA=0.98 and 60% fractional bandwidth. Our proposed platform explores a paradigm for dispersion control with metasurfaces, which may facilitate advanced and scalable dispersion functionalities.

physics.app-ph↗

arXiv2025

Cat-Eye Inspired Active-Passive-Composite Aperture-Shared Sub-Terahertz Meta-Imager for Non-Interactive Concealed Object Detection

Within the feline eye, a distinctive tapetum lucidum as a mirror resides posterior to the retina, reflecting the incident rays to simulate light source emission. This secondary emission property enables felines to be highly sensitive to light, possessing remarkable visual capabilities even in dark settings. Drawing inspiration from this natural phenomenon, we propose an active-passive-composite sub-terahertz meta-imager integrated with a bifocus metasurface, a high-sensitivity radiometer, and a low-power signal hidden radiation source. Benefiting from its aperture-shared advantage, this advanced fusion imaging system, enabled to be deployed by a simplified portable hardware platform, allows for the concurrent acquisition of active and passive electromagnetic properties to extend the target detection category and realize multi-mode fusion perception. Notably, it also enables the extraction of radiation and reflection characteristics without additional calibration modules. Experiments demonstrate the multi-target fusion imaging and localized information decoupling with the tailored field of view and emission energy. This compact and multi-mode fusion imaging system may have plenty of potential for airplane navigation positioning, abnormal monitoring, and non-interactive concealed security checks.

physics.optics↗