Intrinsically chiral metamaterials (ICMMs) exhibiting strong chiroptical responses are promising for chiral sensing and lasing. Streamlining the fabrication process of ICMMs while enhancing the dissymmetry factor ( g ‐factor) is essential to enable large‐scale production and deployment in multifunctional systems. Conventional approaches, such as multi‐step lithography or rotational deposition, are not only complex but also susceptible to fabrication inaccuracies that degrade chiroptical performance. Typically, these methods yield a g ‐factor of only 0.1, which limits their practical utility. Herein, a one‐step lithography strategy based on electron‐beam deposition is introduced. By leveraging the shadowing effect and surface diffusion kinetics during thin‐film growth, 3D ICMMs with diverse topological architectures are fabricated. This approach achieves a record‐high g ‐factor of 1.3 in the visible band. Both the g ‐factor and resonance wavelength can be tuned through geometric design. The versatility of this method is further demonstrated across multiple material systems. As proof of concept, a sensing platform incorporating racemic chiral metamaterials enhance the chiral signal of cysteine enantiomers by three orders of magnitude. These findings open new pathways for developing advanced ICMMs in biosensing and integrated photonics.

Objective Chiral metasurfaces have garnered significant attention for their unprecedented ability to manipulate the spin angular momentum of light, enabling breakthroughs in circular dichroism (CD) spectroscopy, enantiomer sensing, and polarization-multiplexed holography. Despite their potential, most existing designs are passive, restricting their functionality to static optical responses fixed at fabrication. While incorporating phase-change materials (PCMs) offers a compelling route to dynamic tunability, this paper presents a dynamically reconfigurable all-dielectric chiral metasurface based on the low-loss PCM antimony trisulfide. By breaking the in-plane symmetry of Z-shaped meta-atoms to excite symmetry-protected quasi-bound states in the continuum (q-BIC), we aim to achieve giant CD with high-factors and demonstrate active switching of chiroptical responses through the thermal phase transition of , bridging the gap between theoretical high-performance designs and practical experimental realization. Methods The metasurface architecture consists of Z-shaped nanopillars arranged in a periodic array on a silica substrate. The q-BIC mode is excited by breaking the in-plane symmetry of the unit cell via a geometric asymmetry parameter, which opens a radiation channel for the symmetry-protected bound state. Numerical simulations were performed using the finite element method (FEM) to analyze the eigenmodes, multipole decomposition, and far-field optical responses (transmission and CD spectra) under left and right circularly polarized (LCP/RCP) excitation. Experimentally, the samples were fabricated using electron beam lithography (EBL) and thermal evaporation, followed by a lift-off process. The phase transition of was induced via thermal annealing at 300 degrees C. To accurately interpret the experimental spectra, a modified simulation model was developed, incorporating a "double-layer" structure to account for the incomplete phase transition and surface oxidation caused by sulfur volatilization during annealing. Results and Discussions The study reveals that the Z-shaped metasurface supports a high q-BIC resonance governed primarily by the dominant magnetic dipole (MD) mode. FEM simulations demonstrate that increasing the asymmetry parameter transforms the ideal BIC into a leaky q-BIC mode, enabling strong chiral optical responses. Upon thermal annealing, the refractive index of increases, theoretically predicting a significant redshift in the CD spectrum. Experimental measurements confirm a stable CD peak redshift of approximately 45 nm after annealing. While ideal full-crystallization simulations predicted a larger shift and intensity attenuation due to intrinsic material losses, the experimental results exhibited high signal intensity retention. This phenomenon is elucidated by the formation of a thin, low-index, and low-loss surface layer during annealing effectively suppresses the effective extinction coefficient of the meta-atoms and restricts the effective refractive index change, validated by the consistent trends between the modified simulation and experimental data. Conclusions This investigation presents a dynamically reconfigurable chiral metasurface utilizing the phase change material, engineered for active control of CD in the near infrared spectrum. Through the geometric symmetry breaking of Z shaped nanopillars, the design successfully excites q-BIC with high quality factors. The experimental results demonstrate that the thermal phase transition of induces a significant spectral redshift of the chiroptical response while maintaining high signal intensity. This performance retention is attributed to the formation of a low loss oxide surface layer during thermal annealing, which effectively mitigates the optical loss typically associated with the crystalline state. Furthermore, the study elucidates the complex interplay between material processing dynamics and optical performance, proving that partial crystallization and surface oxidation can be leveraged to optimize device efficiency. This research introduces a practical pathway for realizing active chiroptical devices, providing novel perspectives for applications in dynamic polarization display, optical sensing, and reconfigurable photonics.

The graphene–dielectric multilayer architecture constitutes a fundamental and widely utilized platform for sustaining surface polariton (SP) propagation. Owing to their extraordinary prospects in defence critical technologies, including radar-absorbing stealth coatings, high-power microwave shielding, and ultrafast optical switching, SPs have attracted intense and sustained interest. In this study, we develop an environment-adaptive design framework that models wavelength variation as a dynamic environmental change and automatically adjusts the design parameters in response. Our method employs a dynamic multi-objective optimization algorithm augmented with a predictive transfer strategy, optimizing SP coupling efficiency, structural compactness, and fabrication feasibility. Using a population history prediction mechanism, the framework not only adaptively generates multilayer designs across the full visible spectrum without full re-initialization, but also retains and exploits knowledge of how environmental variations influence the distribution of optimal solutions. This enables rapid adjustment of the optimization direction when parameters such as wavelength, angle, or doping change, thus avoiding the need to restart the search from scratch. Comprehensive comparisons demonstrate outstanding robustness under continuous wavelength shifts. The optimized graphene-coated distributed Bragg reflector (DBR) stacks achieve near-perfect absorption (>98%) at each individual wavelength across the visible spectrum. This work not only provides theoretical guidance for SP excitation experiments, but also contributes to the optimization of polariton device design, which is crucial for enhancing the performance of defence-related optical systems.

Tip-enhanced Raman spectroscopy (TERS) suffers from a trade-off between excitation efficiency and background interference, limiting the sensitivity and obscuring higher-order Raman transitions. To overcome this challenge, we introduce a chiral plasmonic fiber tip (CPFT) fabricated via fused tapering and rotational stretching that is internally excited by the fiber vector fundamental mode. By breaking the structural symmetry of the plasmonic fiber tip, the CPFT enables constructive interference of surface plasmon polaritons at the tip apex, producing a tip hotspot with enhanced electric-field intensity and gradient. This design not only amplifies the electromagnetic field but also suppresses far-field background noise, achieving a signal-to-noise ratio 4-fold higher than linearly polarized beam side excitation. Using the CPFT-based TERS platform, we visualized dark-state Raman modes including electric-quadrupole and magnetic-dipole transitions. This approach offers a strategy for high-contrast nanoscale spectroscopy, paving the way toward highly sensitive, low-noise, next-generation TERS systems.

Uncooled mid-wave infrared (MWIR) photodetectors are an important development direction for next-generation infrared technology. However, due to the narrow bandgap and thermal noise, MWIR photo-detection is difficult to achieve with conventional photoconductive (PC) and photovoltaic (PV) photodetectors. This paper proposes a low-damage design based on O+ ion implantation in PbSe, achieving enhanced MWIR photoconductive response. The surface morphology of the nanostructures was observed. The optical bandgap of the thin films became smaller, making them more suitable for mid-infrared radiation detection. Increasing the implantation dose reduced the Urbach energy from 136.9 to 53.37 meV, indicating a reduction in band tail disorder and shallow defect states. An optimal dose (1 & times; 10(18) cm(-2)) achieved a peak responsivity of 2.1 A/W at a wavelength of 4 mu m, with a detectivity of 2.3 & times; 10(9) Jones at 4 mu m, 300 K under bias voltage of 15 V, and chopping frequency of 400 Hz. The photoresponse is attributed to the formation of a built-in carrier separation region and the generation of deep-level traps, thereby enhancing carrier separation and prolonging minority carrier lifetime. Additionally, extremely high carrier mobility (4480-8320 cm(2) V-1 s(-1)) was achieved, which improves the collection efficiency of photogenerated carriers. This work demonstrates a defect engineering strategy through O+ implantation, achieving excellent carrier mobility and responsivity for the high-performance uncooled MWIR photodetector.

The escalating challenge of electromagnetic pollution demands the development of high-performance microwave absorption materials. Herein, a novel Fe3O4@Ti3C2Tx heterostructure is strategically constructed via in-situ chemical co-precipitation to address this issue. Two-dimensional Ti3C2Tx MXene, synthesized by etching Ti3AlC2 with a LiF/HCl mixture, serves as a conductive scaffold with an expanded interlayer spacing and an accordion-like morphology. Magnetic Fe3O4 nanoparticles are uniformly anchored within the interlayers and on the surface of Ti3C2Tx, forming abundant magnetic-dielectric interfaces. The successful intercalation and formation of Fe3O4 are confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. By tailoring the Fe3O4-to-Ti3C2Tx mass ratio, the optimized composite (1:1) achieves an exceptional minimum reflection loss of -50.2 dB at a thin thickness of 2.0 mm, with an effective absorption bandwidth covering 5.1 GHz. This superior performance is attributed to the synergistic effects of the conductive network from MXene, magnetic loss from Fe3O4, optimal impedance matching, and intensified interfacial polarization.

Enhancing optical nonlinearity is crucial for the advancement of compact and efficient photonic devices, enabling new capabilities in frequency conversion, harmonic generation, and all-optical switching. This study investigates the enhancement of epsilon-near-zero nonlinearity in indium tin oxide films through the integration of a quasi-bound state in the continuum (q-BIC) metasurface, which is composed of periodic, centrosymmetric circular hole structures. Near-perfect (>95 %) light absorption under normal incidence is achieved by creating an overlap between the q-BIC and a simultaneous surface lattice resonance mode in the frequency domain through optimizing the structural parameters. Pump-probe measurements reveal significant modulation in transmission (approximate to 20 %) under optical excitation, along with a rapid response time (2.766 ps) suitable for high-speed applications. These findings are anticipated to contribute to the development of advanced optical devices that leverage all-optical modulation for high-speed data processing and communication applications.

Achieving dynamic control of light-matter coupling regimes in plasmonic nanocavities at room temperature is pivotal for quantum technologies but remains challenging due to limitations in polarization-selective excitation efficiency. Here, we demonstrate a polarization-driven reversible switch between weak and strong coupling at the vertical incidence. Leveraging radial vector beam (RVB's) cylindrical symmetry, we generate a confined longitudinal electric field that directly couples to nanoparticle-on-mirror plasmonic modes without sample tilting. This strategy enhances the local electric field by 327-fold (71% higher than linearly polarized beam, LPB) and compresses the mode field volume, amplifying the coupling strength to g = 107 meV, surpassing the strong coupling criterion. Using Rhodamine 800 as a quantum emitter, we demonstrate reversible all-optical switching between a Purcell-enhanced weak coupling regime (under LPB) and a strong coupling regime with 32.8 meV Rabi splitting (under RVB) within the molecule-nanocavity coupling system characterized by highly resolved Rabi splitting in the fluorescence spectra. Further optimization via Au nanoparticle size (R = 40 nm) and collective molecular coupling (N ≥ 5) establishes a ternary synergy for robust quantum control. This noninvasive, polarization-mediated platform enables on-demand manipulation of quantum states for reconfigurable nanophotonic devices.

Uncooled mid-wave infrared photodetectors feature room-temperature operation, high performance, low power consumption, and small size (meeting SWaP(3) standards), making them promising candidates for next-generation infrared detectors. Although there have been numerous reports in recent years on the study of their photo-sensitization mechanisms, a complete understanding of the photo-sensitization process has yet to be established. Here, a temporal mapping of the photo-sensitization process of uncooled PbSe photodetectors is constructed, revealing the evolution mechanism of photo-sensitization and uncovering the transition from a porous grain structure to a core-shell structure. Photosensitization occurs within the range of 11 min < t < 52 min, with the optimal sensitization time being approximately t = 40 min. The mechanism for enhanced photosensitivity is attributed to the formation of pn junction core-shell structures in the grains, which facilitate the separation of photogenerated carriers. The decrease in free carrier concentration caused by sensitization is responsible for the increase in total noise voltage. Density functional theory calculations indicate that iodination and oxidation introduce deep acceptor levels at -0.273 eV below the Fermi level, which can extend carrier lifetime through trap effects. This work provides new insights into the device physics of uncooled mid-wave infrared photodetectors.

Graphene exhibits exceptional nonlinear optical properties, yet its practical applications are hindered by low light-matter interaction efficiency. To address this challenge, this work introduces a hot electron model for graphene, built upon the nonlinear electromagnetic response of carriers with transient admittance and wavevector matching, which enables the design of structures that achieve perfect excitation of surface plasmon-polaritons in graphene at tailored wavelengths and precisely controlled temporal instances during nonequilibrium conductivity dynamics. By fabricating two simple bilayer stratified structures with slight variations in parameters, we experimentally demonstrate precise temporal control over the perfect coupling condition that allows exceptional reflection sensitivity to graphene’s nonlinear conductivity, providing a novel mechanism for active modulation of carrier lifetimes and transport properties. This work establishes a practical strategy for enhancing light-graphene interactions in simple stratified structures, enabling fine monitoring, sensing, and manipulation of emergent nonlinear dynamics, with significant potential for high-performance photonic and optoelectronic devices.

Recently, perfect spatiotemporal optical vortices (PSTOVs) have attracted significant attention due to their topological-charge-independent radius and their ability to carry transverse orbital angular momentum. However, existing studies on PSTOVs remain largely restricted to the simplest annular intensity profiles, limiting their versatility in tailoring light-matter interactions. Extending PSTOVs toward programmable distributions is therefore highly desirable for both fundamental studies and practical applications. To fill this research gap, we propose the concept of generalized perfect spatiotemporal optical vortices (GPSTOVs), whose intensity profiles can be flexibly engineered while preserving their intrinsic "perfect" properties. Unlike previous complex-amplitude modulation approaches, GPSTOV pulses are generated via a pure-phase modulation scheme, enabling higher modulation efficiency and improved energy utilization. By encoding a shape-controllable digital axicon and a vortex phase in the spatiotemporal frequency domain, we experimentally realize a family of polygonal GPSTOV pulses with tunable geometries. The measured spatiotemporal profiles agree well with theoretical predictions. Our results expand the scope of PSTOV research and hold promises for applications in optical communications, particle manipulation, and other fields requiring precise spatiotemporal control of ultrafast light pulses.

To overcome challenges in DNA nucleobase Raman analysis, such as strong backbone signals, spectral overlap, and background noise, we propose a surface-enhanced Raman scattering (SERS) method employing a k-space filter-assisted radial vector beam (RVB) coupled with gold nanospheres (AuNPs). A spatial frequency-modulated RVB is tightly focused to excite AuNPs, producing a localized plasmonic field with a strong longitudinal component that spatially overlaps with DNA segments located in the AuNP near-field region. This configuration achieves strong near-field enhancement while suppressing background noise. The orientation-dependent near-field selection is interpreted through the projection between the local plasmonic field and the vibrational polarizability derivatives of DNA modes. Under orientation-favorable configurations, backbone-related modes with weak field projection are relatively suppressed, whereas nucleobase-related modes with larger projection are preferentially enhanced. Experimental results show effective suppression of backbone signals (900-1250 cm-1) and clearer DFT-assisted assignment of nucleobase-related Raman bands (1350-1500 cm-1). Combined with density functional theory (DFT), overlapping peaks were accurately identified and decoupled. This approach provides a physical mechanism for selective enhancement and noise suppression, offering a label-free optical method for specific DNA nucleobase identification.

The escalating severity of electromagnetic pollution necessitates the development of advanced microwave absorption materials with high efficiency and broad bandwidth. Herein, a novel Fe3O4@Ti3C2Tx heterostructure is rationally designed via an in-situ chemical co-precipitation strategy. Two-dimensional Ti3C2Tx MXene, synthesized by selective etching of Ti3AlC2 using a LiF/HCl mixture, serves as a conductive scaffold featuring expanded interlayer spacing and an accordion-like morphology. Magnetic Fe3O4 nanoparticles are uniformly anchored within the interlayers and onto the surface of Ti3C2Tx, generating abundant magnetic-dielectric interfaces. The successful intercalation and formation of Fe3O4 are corroborated by X-ray diffraction and X-ray photoelectron spectroscopy. By systematically tuning the Fe3O4-to-Ti3C2Tx mass ratio, the optimized composite (1:1) achieves an exceptional minimum reflection loss of −43.03 dB at a thin matching thickness of 2.0 mm, alongside a broad effective absorption bandwidth of 5.1 GHz. This superior performance is attributed to the synergistic interplay between the conductive network of MXene, the magnetic loss contribution of Fe3O4, optimized impedance matching, and intensified interfacial polarization. This work presents a viable pathway for designing high-efficiency microwave absorbers through heterointerface engineering.

Extending the low-loss polariton response of graphene into the visible waveband is of significant interest for advancing applications in nanophotonics and optoelectronics. However, the challenge arises from the relatively low conductivity of graphene in this regime when coupled with common material properties. We reveal that a promising solution involves understanding and optimizing the influence of the dielectric environment on polariton excitation. In this work, both theoretical prediction and experimental evidence are presented, confirming the existence of transverse-electric surface polaritons in graphene within the visible waveband. This discovery is grounded in the optical admittance matching condition, providing a practical approach for achieving complete conversion of excitation photons into surface polaritons at designated wavelengths and incidence angles. By ensuring precise wavevector matching, the polaritons supported by structures specifically optimized for admittance matching exhibit theoretically attenuation-free propagation characteristics. This advancement holds promise for developing ultralow-loss polaritonic devices in the visible and near-infrared ranges.

A highly efficient quadratically nonlinear photodetector (QNPD) is demonstrated based on an InSe/Si p-n heterojunction that uniquely exploits the strong second-order nonlinearity of few-layer InSe integrated onto silicon substrates. Through second-harmonic generation (SHG)-assisted frequency upconversion, the QNPD can detect photons with energies below the InSe/Si electronic bandgap, extending the photodetection range to 1750 nm. Under 1550 nm pulsed excitation, it achieves a high normalized responsivity of 2.3 x 10-3 A W-2 with a clear quadratic photocurrent dependence (I ph proportional to P laser 2). Leveraging this quadratic response, the device functions as a compact optical autocorrelator, enabling accurate characterization of ultrashort pulses of 2.5 and 8.5 ps with a sensitivity of 5 x 10-5 W2, surpassing commercial systems by an order of magnitude. Furthermore, the QNPD's nonlinear response is integrated as an activation function within convolutional neural networks, achieving a digital image classification accuracy of over 98.7% on the MNIST dataset. With the well-developed large-scale growth and transfer of 2D materials with Si, the demonstrated QNPD promises broad potential in integrated nonlinear photonics, ultrafast optical diagnostics, and neuromorphic computing.

Quantum tunneling suppresses extreme nanofocusing in plasmonic cavities while significantly enhancing the electric field gradient. This study employs a plasmonic cavity to drive multipolar Raman scattering of asymmetric thiobenzonitrile, directly observing this phenomenon via the quadrupole-to-dipole Raman intensity ratio. The quantum-corrected model shows that at the subnanometer gap, quantum tunneling simultaneously quenches the electric field enhancement (manifested as a decrease in dipole Raman intensity) and amplifies the electric field gradient effect (resulting in a continuous rise in quadrupole Raman intensity). Experimentally, the introduction of thiobenzonitrile molecules lowers the potential barrier height, enabling quantum tunneling to occur at a larger gap size. This leads to the quadrupole Raman intensity surpassing the dipole Raman intensity (with an enhancement exceeding three orders of magnitude). This work provides new strategies for molecular detection and spectroscopic selection rule manipulation in surface/tip-enhanced Raman spectroscopy and opens avenues for exploring quantum interactions within plasmonic cavities.

Plasmonic nanocavities, known for their ability to enhance light-matter interactions, are further advanced in this study through the design of a nested plasmonic nanocavity. By replacing the conventional flat metal substrate with a silver (Ag) coated nanosphere array, the nested plasmonic nanocavity achieves significant enhancements in both electric-field intensity and its spatial gradient effect under excitation of a linearly polarized beam. This plasmonic nanocavity breaks the dipole selection rule, enabling the visualization of forbidden quadrupole-Raman scattering modes in the 4-thiobenzonitrile molecules. Additionally, the strong localized electric field induces a measurable Stark effect in the dipole-Raman spectra. The nested plasmonic nanocavity thus serves as a powerful platform for probing weak molecular processes, leveraging its dual enhancement of electric-field and gradient effects to unlock new spectroscopic capabilities.

Programmable photonic integrated circuits have developed as a key component for a variety of applications, including advancing optical computing, programmable logic operation, and quantum information processing. However, conventional modulation methods have suffered from significant limitations, including restricted refractive index tunability and substantial static power consumption, which impedes their large-scale integration. In this work, we demonstrate ultralow-loss programmable silicon photonics enabled by the phase-change material Sb2S3. Utilizing inverse design techniques, we introduce pixelated Sb2S3 patterns onto a compact device footprint of only 4 x 18 mu m to precisely modulate optical transmission. Through targeted programming of these pixel patterns, we experimentally demonstrate four distinct broadband power distribution ratios (90:10, 80:20, 70:30, and 60:40), achieving a maximum extinction ratio of 12 dB at a central wavelength of 1550 nm for the 90:10 configuration. The measured power distribution ratios closely match inverse design predictions, with deviations of approximately 3%. Based on this approach, we further validated the capability of multi-input/output linear optical transformation devices. This scalable, energy-efficient, and nonvolatile photonic platform paves the way for large-scale optical computing, neuromorphic photonics, and next-generation reconfigurable photonic architectures.

Breaking the electric-dipole selection rule in molecular spectroscopy is of great significance for manipulating vibrational state transitions and developing unconventional photofunctions of molecules. In this study, a static plasmonic nanocavity composed of a gold (Au) nanosphere on a silver (Ag) substrate was excited using a radial vector beam with a tunable spatial frequency component. The resulting nanocavity-plasmonic mode has a significantly enhanced electric-field gradient to visualize the electrical-quadrupole transition in the molecule. The static plasmonic nanocavity is tunable by regulating the spatial frequency component of the excitation beam. Thus, the interaction between the electric field/electric-field gradient of the nanocavity-plasmonic mode and the molecular polarizabilities has been accurately identified. This innovative nanospectral platform provides unique opportunities for studying weak physical and chemical processes in molecules.