Observation of the Generalized Kerker Effect Mediated by Quasi-Bound States in the Continuum.

The generalized Kerker effect (GKE) arising from the interference of high-order multipoles has attracted more interest due to its direct correlation with various functionalities in nanophotonics. The realization of the GKE at oblique incidence is highly desired yet remains underexplored. Herein, we report the experimental observation of the GKE by leveraging quasi-bound states in the continuum (QBICs) supported by a silicon metasurface.

Achieving asymmetry parameter-insensitive resonant modes through relative shift-induced quasi-bound states in the continuum.

High-Q resonances in metasurfaces, stemming from symmetry-protected bound states in the continuum (BICs), have proven to be effective for achieving high-performance optical devices. However, the properties associated with symmetry-protected BICs are inherently limited, as even a slight variation in the asymmetry parameter leads to a noticeable shift in the resonance location. Herein, we introduce the concept of relative shift-induced quasi-BICs (QBICs) within dimerized silicon (Si) meta-lattices (DSMs), which can be excited when a nonzero relative shift occurs, a result of in-plane inversion symmetry breaking and Brillouin zone folding within the structure.

Unidirectional self-imaging in multiple shifted photonic crystal interfaces.

In this study, we investigate the unidirectional self-imaging phenomenon in the shifted photonic crystal (PC) heterostructure. A spin-locked topological edge state, which originates from the mismatch of the Wannier center positions, can propagate along the shifted PC interface without backscattering. When the neighboring shifted PC interfaces are close enough, the coupling between the edge states happens, and coupled edge states (CES) can be found.

Color Generation and Polarization-Sensitive Encryption by Laser Writing on Plasmonic Reflector Arrays.

Plasmonic color printing presents a sustainable solution for vibrant and durable color reproduction by leveraging the light-manipulating properties of nanostructures. However, the fabrication of plasmonic nanostructures has posed challenges, hindering widespread adoption. In this paper, we introduce plasmonic reflector arrays (PRAs) composed of three layers─Ag nanoparticles (NPs), an AlO spacer, and an Ag reflector─deposited via physical vapor deposition (PVD).

Flexible design of chiroptical response of planar chiral metamaterials using deep learning.

Optical chirality is highly demanded for biochemical sensing, spectral detection, and advanced imaging, however, conventional design schemes for chiral metamaterials require highly computational cost due to the trial-and-error strategy, and it is crucial to accelerate the design process particularly in comparably simple planar chiral metamaterials. Herein, we construct a bidirectional deep learning (BDL) network consists of spectra predicting network (SPN) and design predicting network (DPN) to accelerate the prediction of spectra and inverse design of chiroptical response of planar chiral metamaterials. It is shown that the proposed BDL network can accelerate the design process and exhibit high prediction accuracy.

Phase-change metasurfaces for dynamic control of chiral quasi-bound states in the continuum.

Chiral quasi-bound states in the continuum (QBIC) offer novel mechanisms to achieve intrinsic chiroptical responses. However, current studies on chiral QBIC metasurfaces are restricted to the excitation of intrinsic chirality and fail to dynamically control its circular dichroism (CD) responses. Herein, we construct a phase-change metasurface based on paired GeSbTe (GST) bars to demonstrate the dynamic control of the CD responses of chiral QBIC.

Topological transport in heterostructure of valley photonic crystals.

We propose a heterogeneous structure, which are composed of two valley photonic crystals (VPCs) with opposite valley Chern numbers and air channel. With the increasing width of the air channel, valley-locked waveguide modes are found in topological bandgap by analyzing energy bands. Finite element method (FEM) simulation results show that the fundamental and high order modes are valley-locked, propagating unidirectionally under the excitation of chiral source, and possess higher flux compared to the valley-locked topological edge state in the domain wall.

Simulated annealing algorithm with neural network for designing topological photonic crystals.

In this work, we utilize simulated annealing algorithm with neural network, to achieve rapid design of topological photonic crystals. We firstly train a high-accuracy neural network that predicts the band structure of hexagonal lattice photonic crystals. Subsequently, we embed the neural network into the simulated annealing algorithm, and choose the on-demand evaluation functions for optimizing topological band gaps.

Active control of resonant asymmetric transmission based on topological edge states in paired photonic crystals with a GeSbTe film.

For many high-precision applications such as filtering, sensing, and photodetection, active control of resonant responses of metasurfaces is crucial. Herein, we demonstrate that active control of resonant asymmetric transmission can be realized based on the topological edge state (TES) of an ultra-thin (GST) film in a photonic crystal grating (PCG). The PCG is composed of two pairs of one-dimensional photonic crystals (PCs) separated by a GST film.

SPR Sensor Based on a Concave Photonic Crystal Fiber Structure with MoS/Au Layers.

We propose a surface plasmon resonance (SPR) sensor based on the concave photonic crystal fiber (PCF) coated with molybdenum disulfide (MoS) and Au layers, which can detect the refractive index (RI) of the analyte. The finite element method (FEM) was used to verify our design, and the loss spectra of the fundamental mode are calculated. Compared with the SPR sensor with only a Au layer, the wavelength sensitivity can be improved by from 3700 to 4400 nm/RIU.

Mid-infrared circular-polarization-sensitive photodetector based on a chiral metasurface with a photothermoelectric effect.

Photothermoelectric conversion in chiral metasurfaces with thermoelectric material provides an effective way to achieve circular polarization recognition. In this paper, we propose a circular-polarization-sensitive photodetector in a mid-infrared region, which is mainly composed of an asymmetric silicon grating, a film of gold (Au), and the thermoelectric layer. The asymmetric silicon grating with the Au layer achieves high circular dichroism absorption due to a lack of mirror symmetry, which results in a different temperature increasing on the surface of the layer under right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) excitation.

Multimode interference in topological photonic heterostructure.

In this Letter, topological photonic heterostructures, which are composed of finite-size photonic crystals with different topological phases, are proposed. The coupled topological edge states (CTESs), which originate from the coupling between topological edge states, are found. By using the finite element method, the multimode interference effect of CTESs is predicted and investigated.

Lithography-free tunable absorber at visible region via one-dimensional photonic crystals consisting of an α-MoO layer.

Flexible control of light absorption within the lithography-free nanostructure is crucial for many polarization-dependent optical devices. Herein, we demonstrated that the lithography-free tunable absorber (LTA) can be realized by using two one-dimensional (1D) photonic crystals (PCs) consisting of an α-MoO layer at visible region. The two 1D PCs have different bulk band properties, and the topological interface state-induced light absorption enhancement of α-MoO can be realized as the α-MoO thin film is inserted at the interface between the two 1D PCs.

The Influence of Hypothermia Hibernation Combined with CO Anesthesia on Life and Storage Quality of Large Yellow Croaker ().

We explore the feasibility of the long-term transportation of live large yellow croakers () using the combined method of CO anesthesia and hypothermia hibernation, and its effect on the quality of recovered fish stored at 4 °C. Fish treated with CO anesthesia at a 2 ppm/s aeration rate were cooled at 3 °C/h to hibernate survived for 36 h at 8 °C in seawater. This method resulted in better survival rates and time, and a lower operational time than hypothermia hibernation or CO anesthesia methods.

Ultrabroadband and ultrathin absorber based on an encapsulated T-shaped metasurface.

Ultrabroadband absorbers are vital for applications such as solar energy harvesting and integrated optoelectronic devices. Herein, we design, fabricate and characterize a novel ultrabroadband and ultrathin absorber based on the encapsulated T-shaped metasurface (ETM). The ETM consists of a 20 nm Cr film and a Cr substrate sandwiched by the T-shaped polymethyl methacrylate (PMMA) arrays.

High-quality-factor dual-band Fano resonances induced by dual bound states in the continuum using a planar nanohole slab.

In photonics, it is essential to achieve high-quality (Q)-factor resonances to improve optical devices' performances. Herein, we demonstrate that high-Q-factor dual-band Fano resonances can be achieved by using a planar nanohole slab (PNS) based on the excitation of dual bound states in the continuum (BICs). By shrinking or expanding the tetramerized holes of the superlattice of the PNS, two symmetry-protected BICs can be induced to dual-band Fano resonances and their locations as well as their Q-factors can be flexibly tuned.

Dual-frequency unidirectional reflectionless propagation in a non-Hermitian graphene plasmonic waveguide-cavity coupling system.

We theoretically investigate a controllable dual-frequency unidirectional reflectionlessness at exceptional points by applying external voltage in a graphene plasmonic waveguide system. The system consists of a graphene waveguide and two end-coupled resonators. COMSOL simulation results show that the reflection of edge fundamental graphene surface plasmon polaritons mode for forward (backward) incidence is near to zero at frequency 24.

3D fluorescence confocal microscopy of InGaN/GaN multiple quantum well nanorods from a light absorption perspective.

A nanostructure of InGaN/GaN multiple quantum well (MQW) nanorods (NRs) was fabricated using top-down etching with self-organized nickel (Ni) nanoparticles as masks on the wafer. The optical properties of InGaN/GaN MQW NRs were discussed by experiment and theory from a light absorption perspective. Three-dimensional (3D) optical images of NRs were successfully obtained by confocal laser scanning microscopy (CLSM) for physical observation of the optical phenomenon of InGaN/GaN MQW NRs.

Anisotropic Photonics Topological Transition in Hyperbolic Metamaterials Based on Black Phosphorus.

Based on in-plane anisotropy of black phosphorus (BP), anisotropic photonics topological transition (PTT) can be achieved by the proposed hyperbolic metamaterials structure, which is composed of alternating BP/SiO multilayer. Through effective medium theory and calculated iso-frequency contour, PTT can be found by carefully choosing the incident plane and other parameters. With the finite element method and transfer matrix method, a narrow angular optical transparency window with angular full width at half maximum of 1.

Tunable asymmetric transmission across stretchable chiral metamaterial.

A stretchable chiral metamaterial with L-shaped and T-shaped Au patterns (SCMM-LT) is proposed to generate asymmetric transmission (AT) for circularly polarized waves on the polydimethylsiloxane substrate in the mid-infrared region. The peak value of AT can reach 50.02% at the resonance wavelength of 19.

Dynamically tunable directional subwavelength beam propagation based on photonic spin Hall effect in graphene-based hyperbolic metamaterials.

Photonic spin Hall effect (PSHE) of type II hyperbolic metamaterials is achieved due to near filed interference, which provides a way to decide the propagation direction of subwavelength beam. In this paper, we propose graphene-based hyperbolic metamaterials (GHMMs), which is composed of the alternating graphene/SiO multilayer. The numerical results show that when a dipole emitter is placed at the boundary of the GHMMs, the subwavelength beam with λ/40 full-with half maximum can be excited and propagates along the left or right channel, which is dependent on polarization handedness.

Mode Conversion of the Edge Modes in the Graphene Double-Ribbon Bend.

In this paper, a new kind of graphene double-ribbon bend structure, which can support two edge graphene surface plasmons (EGSPs) modes, is proposed. In this double-ribbon bend, one edge mode can be partly converted into another one. We attribute the mode conversion mechanism to the interference between the two edge plasmonic modes.