Conventional microwave absorbers, with their fixed operating frequencies and narrow bandwidths, are fundamentally limited in the face of advancing multifrequency radar systems. Strain tuning is highly favored as a dynamic regulation strategy because of its simple operation and rapid response. However, achieving broadband tunability and strong low-frequency absorption in strain-tunable microwave absorbers remains challenging, as even slight compression can lead to significant increases in conductivity. Herein, we develop a spherical-pore-structured graphene aerogel (SPGA) through a microbubble-templating method. The spherical-poretopology effectively suppresses strain-induced percolation of conductive networks, rendering the electrical conductivity only weakly dependent on strain. SPGA achieves dynamic frequency tuning across 3.6-18GHz while maintaining strong absorption under compressive strains of up to 70%. Simultaneously, it delivers enhanced low-frequency absorption with an effective absorption bandwidthof 2.56GHz, spanning 91% of the low-frequency microwave spectrum. These results demonstrate the potential of topology-guided structural design for strain-tunable microwave absorption and suggest a viable route for the rational design of intelligent microwave absorbers.

Large depth range nanoscale axial resolution surface profile measurement using narrow bandwidth spectral domain-OCT

In coherent diffraction imaging (CDI), the coherence properties of photons play critical roles in obtaining structural information from specimens without using lenses. While the impact of coherence has been widely studied in CDI, it has not been systematically investigated within the specific framework of X-ray free-electron laser (XFEL)-CDI. Here, we examined the relationship between the transverse and temporal coherence of XFEL pulses and the quality of image reconstruction using XFELs. Specifically, we investigated the properties of self-amplified spontaneous emission and self-seeding beams at an X-ray energy of 5 keV by collecting diffraction patterns from a single gold nanoparticle. Furthermore, the quality of the reconstructed images obtained using the two beam modes was compared. Our results demonstrate that the self-seeding beam offers more reliable image reconstruction that is attributable to the narrower bandwidth of the incident X-rays. This study highlights the advantages of utilizing a self-seeding beam in CDI experiments, particularly for enhancing the reliability and quality of image reconstruction.

Luminescent solar concentrators (LSCs) are large-area, high-efficiency solar energy-harvesting devices with considerable potential in building-integrated photovoltaics. Their performance is dominantly governed by the luminescent materials, which determine the light-harvesting efficiency, spectral conversion capability, and long-term operational stability of the devices. As important luminescent materials, metal-organic frameworks (MOFs) have advantages for LSC applications, including high luminescent efficiency, excellent stability, low environmental impact, and facile synthesis. Nevertheless, despite these favorable characteristics, the exploration of MOF-based luminescent materials in LSC devices remains relatively limited. In this work, a red-emitting MOF, designated as SCU-UEu-2, was synthesized with high reaction yield and good feasibility for large-scale production. Compared with Eu-based MOFs, SCU-UEu-2 shows a broader excitation range, while in contrast to quantum dots, it exhibits a narrower emission bandwidth. Moreover, the minimal spectral overlap between its absorption and emission effectively suppresses reabsorption energy losses, thereby improving LSC efficiency. The photoluminescent quantum yield (PLQY) of the SCU-UEu-2 reaches 90.28%. As a proof of concept, an LSC device incorporating SCU-UEu-2 was fabricated and systematically evaluated. Under simulated sunlight illumination (100 mW·cm-2), the device achieved a maximum optical conversion efficiency (ηopt) of 9.9%, demonstrating strong potential of MOF-based luminescent materials for high-performance LSC applications.

Surface-enhanced infrared absorption (SEIRA) is a sensitive and orientation-selective technique that is theoretically suitable for in-depth chiral recognition studies related to molecular conformations. However, the aforementioned concept is challenging to realize because of the narrow bandwidth and weak near-field strength of plasmonic antennas (PAs). Herein, a seed-mediated growth method for synthesizing ultrabroadband (400-4000 cm-1) submicrometer Au superparticles was proposed. In this work, the issue of uncontrolled particle growth due to secondary nucleation is thoroughly discussed, which is a common phenomenon during the synthesis of large-scale particles. Thus, tunable Au superparticles are acquired through precise kinetic regulation and a phase transfer strategy. Furthermore, the distinctly different SEIRA signal intensities of various chiral enantiomers demonstrate the reliability of this approach and the sensitivity of this PA. This work provides insights into the general issue of seed-mediated synthesis of large-scale particles while also expanding the materials and methods toolkit for advanced molecular chiral research.

Designing compact, high-gain antennas at 400 MHz is challenging due to large size, narrow bandwidth, and low efficiency. This work proposes an interaction-driven Artificial Magnetic Conductor-Defected Ground Structure (AMC-DGS) microstrip antenna for subsurface communication. The design exploits electromagnetic interaction between the slot-type DGS, radiating patch, and AMC surface with spacer layer for performance enhancement. The DGS functions not only for impedance tuning or to attain polarization purity but also as an active radiator, enabling current redistribution and higher order mode perturbation. This interaction, combined with composite superposed mode (CSM) excitation and orthogonal slot radiation, achieves a 400 MHz band (379–419 MHz) with 10.2% bandwidth and 6.5 dBi peak gain. Additionally, a higher-order mode generates a second band at 700 MHz (700–714 MHz) with 2% bandwidth and 6.1 dBi gain. The antenna maintains stable broadside radiation with efficiencies of 98% and 70% at 400 MHz and 700 MHz, respectively. The proposed AMC-DGS antenna provides a compact, dual-band solution for subsurface sensing, Wireless Underground Sensor Networks (WUSN), Internet of Underground Things (IoUT), Ground Penetrating Radar (GPR), and other low-frequency communication systems.

Inverse Thomson scattering from laser-plasma accelerators offers a pathway to compact, tunable MeV γ-ray sources for reduced-dose radiography and enhanced performance in nuclear resonance fluorescence (NRF)-based isotope identification. However, photon yield and spectral quality are often limited by constraints on interaction geometry and scatter-laser tunability. Here we demonstrate a MeV γ-ray source based on a dual-laser inverse Thomson scattering configuration driven by a 100-TW laser-plasma accelerator. Electron beams tunable from 122 to 204MeV with [Formula: see text]mrad divergence and [Formula: see text]mrad pointing stability generate γ rays with peak energies from 276keV to 1.2MeV and yields up to [Formula: see text] photons per shot. By independently controlling the interaction position and the scatter-pulse duration, we experimentally match the scatter pulse to the walk-off-limited interaction length. Extending the scatter pulse to 200fs increases photon production by approximately [Formula: see text] while maintaining operation in the linear Thomson regime, thereby preserving narrow spectral bandwidth and controlled radiation divergence. Radiographic characterization demonstrates MeV-level penetration and [Formula: see text]mm spatial resolution, while stable operation is sustained over multi-hour timescales across multiple days. These results show that interaction-length optimization provides a scalable strategy for improving photon yield, spectral control, and operational stability in compact laser-plasma-accelerator-driven γ-ray sources.

Efficient electromagnetic absorption is essential for optical modulation and integrated photonic devices and can be significantly enhanced by interference-assisted resonant nanostructures. Here, we propose a borophene-dielectric nanostructure operating at telecommunication wavelengths to realize tunable coherent perfect absorption (CPA). The structure supports guided-mode resonances (GMRs), which generate strong near-field enhancement near the borophene layer and promote efficient light-matter interaction. Under single-port excitation, resonance-enhanced absorption with directional asymmetry is observed, yielding peak absorption of 42.5% and 57.4% for opposite incidence directions. Under dual-port coherent excitation, CPA with a narrow bandwidth of 0.82 nm occurs at 1549.8 nm when the scattering matrix satisfies the zero-determinant condition. At the CPA wavelength, the absorption can be continuously tuned from below 10% to above 99.9% by adjusting the phase difference between the two incident beams. Electrical tuning of the borophene carrier concentration further enables a resonance shift of 12.4 nm while maintaining absorption above 95%, nearly fifteen times larger than the intrinsic CPA resonance linewidth. Structural asymmetry further leads to unequal external coupling strengths, enabling asymmetric interferometric light-light control under unequal-intensity excitation. These results demonstrate a compact platform for phase-controlled absorption and coherent optical switching in integrated photonic systems.

The reflection coefficient measurement of the RF signal generator output is clear when the signal generator output is turned off, as no interfering signal is present. However, measuring the reflection coefficient while the signal generator output is turned on creates complexity, as the generator’s output power can interfere with the reflected signal. A vector network analyzer (VNA) is the reference instrument for measuring the reflection coefficient, capturing both the magnitude and phase of scattering parameters. For measuring the active output of a signal generator, the signals created by the generator and the VNA must be isolated to prevent signal mixing and interference. This paper proposes a unique method to measure the output reflection coefficient of an RF signal generator when the output is on, using a VNA configured for one port reflection coefficient measurement. The method involves tuning the VNA receiver to a frequency slightly offset to the generator’s output. Simultaneously, selecting a narrow intermediate frequency bandwidth (IFBW) reduces the receiver’s noise floor and also eliminates out-of-band interference. As a result, the VNA and the generator operate in different frequency bands to avoid interferences between them, enabling accurate magnitude and phase measurements. To automate the process, a Windows-based software has been developed. This software automates the measurement sequence, controls generator power levels and VNA sweep parameters, captures both the magnitude and phase of the reflection coefficient, and records the result data. It also supports measurement at different output power levels, enabling characterization across a wide range of operating conditions.

Abstract We propose the optical simulation of the Lieb–Liniger interaction using one-dimensional (1D) stationary light polaritons (SLPs) with nonlinear self-interaction. Our analysis reveals that the dark-state polariton (DSP) mode of the self-interacting SLP satisfies a Schrödinger-like equation exhibiting the Lieb–Liniger interaction, where both the effective mass and interaction strength can be tuned optically. We demonstrate the transition of the Lieb–Liniger interaction from a repulsion-dominant regime to a thermalization-dominant regime using experimentally achievable parameters. This results in the second-order correlation of the DSP mode spanning from anti-bunching to bunching statistics. By advancing the quantum simulation of the Lieb–Liniger model, our work opens new avenues for exploring complex Lieb–Liniger physics, such as interaction quenching and multi-particle bound states. Moreover, it lays the groundwork for developing novel single-photon sources operating in the anti-bunching regime, featuring narrow bandwidth, directional emission, and built-in quantum memory functionality.

Photoacoustic tomography as an optical-ultrasound hybrid imaging modality provides rich optical contrast over the extended penetration depth of biological tissues, enabling multiscale multicontrast structural and functional imaging. However, inherent limitations in the state-of-the-art piezoelectric transducer arrays of the photoacoustic tomography, including size-dependent sensitivity, narrow bandwidth, and high material rigidity, compromise the resolution, penetration depth, and functional assessment precision. Here, an arc-shaped fiber ultrasound transducer array with a sheet-like ultrasound focus is demonstrated for photoacoustic computed tomography. At the ultrasound focus, a low detection limit of ~ 5.2 Pa and a dual-frequency response spanning several octaves are achieved. Whole mouse brain imaging with a depth up to ~ 1.2 cm and a spatial resolution of ~ 70 μm in the cerebral cortex region is showcased. The blood oxygen saturation within the entire mouse brain and the brain tumors is visualized, and the assessment precision is improved by leveraging the dual-frequency response of the transducer array. The centimeter-scale imaging depth, fine resolution of the cerebral vessels, and improved precision in the blood oxygenation evaluation make the fiber-array photoacoustic tomography a competitive candidate to the sought-after magnetic resonance imaging and ultrasound localization microscopy for brain functionality study and disease diagnosis.

Recent biomedical and wearable tech advances enable real-time health monitoring, but their adoption is limited by dependence on short life span, bulky batteries that require frequent replacement. This persistent limitation not only hinders device miniaturization and long-term functionality but also poses significant patient burdens, especially for implantable devices requiring invasive replacement surgery. Vibration energy harvesting offers a promising alternative by converting biomechanical energy from body movements into sustainable electrical power. This review comprehensively examines the scope, mechanisms, recent advances and challenges in vibration energy harvesters (VEHs) for biomedical and wearable applications. The four primary transduction mechanisms: piezoelectric, electrostatic, electromagnetic, and triboelectric were analyzed with a focus on their operational principles, material configurations, and biocompatibility considerations, followed by a comparative assessment of their performance, miniaturization potential, and integration challenges. The paper highlights cutting-edge developments from the past five years, including hybrid systems that synergize multiple mechanisms to enhance efficiency and adaptability for low-frequency human motion. The significance of this field lies in its potential to enable a new generation of truly autonomous, self-sustaining medical devices, thereby revolutionizing patient care by eliminating power supply as a constraint. Despite significant progress, critical technical, design, and commercialization barriers persist, such as low power output, narrow operational bandwidth, reliability concerns, and stringent biocompatibility requirements. Further impeding widespread adoption are manufacturing costs, regulatory hurdles, and market competition with conventional batteries. By addressing these challenges with material innovations, advanced modeling, and efficient power management circuits, VEHs can revolutionize self-powered wearables. Future success hinges on interdisciplinary collaboration to bridge lab research and commercial viability for autonomous healthcare integration. This work stands out by synthesizing a critical analysis of both the technological promises and the practical commercialization hurdles, providing a holistic roadmap for researchers and industry stakeholders aiming to make self-powered biomedical devices a clinical reality. • Explores the potential of vibration energy harvesters (VEHs) for sustainable healthcare. • Reviews mechanisms and material advancements with a focus on biocompatibility. • Highlights key breakthroughs in VEHs efficiency, miniaturization, and power output for medical applications. • Identifies critical challenges limiting market adoption and proposes solutions. • Outlines actionable steps to accelerate VEHs integration into real-world healthcare systems.

An active inference explanation of discriminatory cognition with regard to social attitudes and harmful behaviour.

Ultrabroadband photodetectors (UB-PDs) are seeing burgeoning deployment across a lot of technologies, including artificial intelligence, healthcare, optical communications, and biomedical imaging, which prompts urgent demands for high-performance UB-PDs. However, the existing photodetectors usually suffer from limitations of narrow operational bandwidth and low sensitivity at room temperature. SnBi2Te4, a novel topological insulator intercalation material, exhibits a narrow bandgap, unique surface-state conductive transport properties, and a tunable band gap, making it an ideal candidate for room-temperature ultrabroadband photodetection. In this study, we synthesize high-quality layered SnBi2Te4 crystals using the Chemical Vapor Transport (CVT) method. The fabricated detector achieves high-performance broadband detection from visible to terahertz (THz) light through synergistic mechanisms of the conventional photoelectric effect and the electromagnetic-induced well effect. In the visible-infrared region, the photodetector shows a noise equivalent power of 8.5 pW·Hz-1/2 with the response time of 70 µs and responsivities of 19.4 A·W-1 at 980nm and 13.9 A·W-1 at 635nm, respectively. Additionally, the current responsivity (Ri) of the SnBi2Te4 photodetector is 0.117 A·W-1 at the mid-wave infrared (MWIR, 3µm) band and 0.063 A·W-1 at the long-wave infrared (LWIR, 10.6µm) band. In the terahertz region, this detector achieves sensitive detection across the 0.02-0.519 THz spectral band, exhibiting an ultrafast response time of 1.83 µs. Finally, the excellent performance of the detectors is demonstrated by high-resolution THz transmission imaging experiments at room temperature. Our study confirms the significant advantages of SnBi2Te4 for ultrabroadband room-temperature photodetection.

We demonstrate an acousto-optic sensing approach that integrates a dual-core As2Se3 nanofiber interferometer within a surface acoustic wave (SAW) cavity to achieve externally driven intermodal phase modulation distinct from spontaneous forward Brillouin scattering. Introducing a thin liquid coupling layer allows Rayleigh SAW to satisfy the leaky wave condition causing radiation into the liquid, converting into a leaky SAW, enabling modulation sidebands and narrow detection bandwidths approaching the Hz level. Interferometric sensitivity is improved through coherent detection with balanced receivers and polarization biasing, acting as a common-mode noise rejection system, minimizing the optical noise floor to within ∼1 dB of the photodetector dark-noise limit.

Frequency-domain photoacoustic microscopy with resonant transducer and interferometric modulation for high-reliability sO2 imaging.

HighlightsWhat are the main findings?A flexible microstrip antenna with beveled meandering and a partial ground plane broadens its bandwidth from 0.612–0.625 GHz to 0.346–2.0 GHz while shrinking its footprint to 75.3% of its original size.The improved whale optimization algorithm (I-WOA), which combines Sobol sequence initialization with Q-learning, efficiently optimizes the antenna’s structural parameters for simultaneous bandwidth maximization and size minimization.What are the implications of the main findings?The novel sensor overcomes the installation rigidity of conventional microstrip antennas by enabling non-invasive, broadband RF detection of partial discharges in both power transformers and cable joints.The practical advantage of a flexible substrate for curved equipment surfaces is evidenced by a 14% increase in response amplitude when the antenna is conformally wrapped around a cable joint.Partial discharge (PD) detection effectively identifies insulation defects in power equipment. Radio frequency (RF) methods for PD detection offer promising advantages due to their non-invasive measurement capability and ability to locate discharge sources. However, microstrip antennas used as RF sensors for PD detection suffer from narrow bandwidth and limited installation flexibility. To address these limitations, this paper presents a novel flexible microstrip antenna design. By incorporating a partial ground plane and oblique-cut meandering techniques and optimizing the structural parameters using an improved whale optimization algorithm (I-WOA), the operating bandwidth is expanded from 0.612–0.625 GHz to 0.346–2.0 GHz, while the overall size is reduced to 75.3% of its original dimensions. The antenna’s performance was validated through GTEM cell measurements and PD calibration pulse tests, confirming its suitability for RF detection of PD in power equipment such as transformers and cable joints. Notably, when the antenna was conformally wrapped around a cable joint, the response amplitude increased by 14%. This study contributes to the development of a low-cost, broadband, and flexibly installable RF sensor for partial discharge detection.

To address the difficulty of suppressing low-frequency line spectra in underwater vehicle radiated noise and the narrow operating bandwidth of conventional linear vibration absorbers with fixed tuning frequencies, this paper proposes a flexible hinge-type nonlinear energy sink (NES). First, a double-slotted flexible hinge-type NES structure is presented. Static mechanical analysis shows that the structure exhibits cubic stiffness characteristics near the static equilibrium position. Second, the IHB method is employed to characterize the periodic responses of the NES system. The effects of NES mass, stiffness, and damping on the amplitude-frequency response and vibration suppression performance are then investigated in detail. Subsequently, local optimization is performed to determine the optimal damping and stiffness parameters of the NES. The optimized NES shows strong robustness against variations in excitation frequency and amplitude. Finally, a prototype of the flexible hinge-type NES is fabricated, and a vibration test platform is established for experimental validation. Both simulation and experimental results show that the NES reduces the first-order resonance peak near 5.00 Hz by approximately 8.17 dB, decreases the average line-spectrum level over 4.43–5.82 Hz by about 3.74 dB, and broadens the vibration absorption bandwidth by approximately 27.8%. Compared with an equivalent linear dynamic vibration absorber, the NES provides better broadband vibration absorption performance. In addition, the NES can shift the resonance frequency of the coupled system and induce a strong modulation response.

This paper presents a frequency selective rasorber (FSR) featuring a large frequency ratio (FR) dual passbands and ultra-wideband absorption. Existing dual-passband FSRs are typically limited by small frequency ratios (FR) and narrow absorption bandwidths, restricting their application in large FR dual-frequency integrated antenna systems. To overcome these limitations, the proposed FSR cascades two lossy layers with a low-complexity frequency selective surface (FSS). The FSS layer is based on a slot-type single passband FSS, and dual passbands with a large FR are achieved by incorporating T-shaped slots, while the lossy layers decouple the high- and low-frequency passband resonators by physically separating them with absorbing resonant structures, allowing them to independently determine their respective passband frequencies. Furthermore, cascading two lossy layers with distinct resistances ensures ultra-wideband out-of-band impedance matching. Experimental results demonstrate dual passbands at 11.64 GHz and 28.21 GHz with a large FR of 2.42 and low insertion losses of 0.92 dB and 0.88 dB, respectively. The design achieves an overall absolute absorption bandwidth of 20.26 GHz, comprising two bands with fractional bandwidths of 116.70% and 62.57% for absorptivity greater than 80%. The measured results align well with simulations, confirming the effectiveness of the proposed method for high-performance stealth radomes.

Integrated microwave photonic filters (MPFs) are essential components for enabling broadband radio frequency signal processing. However, owing to the deficiency of large-bandwidth electro-optic (EO) modulation devices, traditional integrated MPFs based on III-V or silicon photonic platforms face significant challenges in achieving ultra-wideband operation, particularly when extending to the V/E bands and sub-terahertz range. In this paper, we address this limitation and experimentally demonstrated an integrated MPF with ultra-wideband tunability exceeding 110 GHz and high filtering resolution at the sub-GHz level, based on a monolithic thin-film lithium niobate (TFLN) platform. The TFLN MPF chip comprises a large-bandwidth phase modulator and a low-loss microring resonator (MRR) with an intrinsic Q of 2.62 × 106, achieving bandpass filtering responses based on phase-modulation to intensity modulation (PM-IM) conversion mechanism. By precisely controlling the wavelength deviation between the laser carrier and microring resonance, this MPF achieves continuous tuning of the center frequency from near DC to 110 GHz, while maintaining narrow filtering bandwidth (<350 MHz) across the entire tuning range. Compared to state-of-the-art integrated solutions, the proposed TFLN MPF improves the filtering tunable range by nearly two times and extends the operating frequency of MPF beyond 110 GHz for the first time. Our work establishes a foundation for future millimeter-wave and sub-terahertz applications, ranging from 6G ultra-high-speed wireless communication to high-resolution radar.