A surface plasmon resonance (SPR) enables label-free real-time biomolecular detection but is hindered by low throughput, limited sensitivity, and narrow dynamic range. Here, we report a polarization-controlled intensity-modulated SPR imaging (SPRi) system integrated with a 12-channel microfluidic chip to address these limitations. The working mechanism exploits the phase difference between s- and p-polarized light upon SPR excitation: p-polarized light induces SPR with an additional phase shift, whereas s-polarized light does not participate, converting incident linearly polarized light into elliptically polarized light. By incorporating a polarizer, a quarter-wave plate, and an analyzer, refractive index (RI) changes are transduced into multistage amplified signals: from phase difference to polarization state variation and finally to light intensity change, thereby significantly enhancing the sensitivity. The system achieves an RI sensitivity of 24,300 ± 426 au/RIU over the linear range of 1.337-1.370 RIU, a resolution of (9.96 ± 0.32)×10-7 RIU across a dynamic range of 1.331-1.410 RIU, and a baseline drift of 0.63 ± 0.02 RU/min (1 RU = 10-6 RIU). Real-time self-referencing effectively suppresses noise, yielding an RMS value of 0.0242. Biomolecular assays demonstrate a sensitivity of 0.06586 au/(μg/mL) for mouse immunoglobulin G (IgG) and a detection limit of 1.56 pg/mL for D-biotin. This platform offers a robust solution for high-throughput applications in biomedicine, environmental monitoring, and pharmaceutical development.

Isothermal amplification technology (IAT), an enzymatic nucleic acid amplification technique conducted at a constant temperature, has garnered significant attention due to its simplicity, rapidness, and reduced equipment requirements in molecular biology. However, the current quantitative analysis of IAT results predominantly relies on dye-labeling methods, which not only complicate the operation but also increase the requirements for instrumentation. To address the pressing needs for highly sensitive, label-free, and constant-temperature detection in IAT, we propose and validate a dual resonance surface plasmon resonance (SPR) sensing platform with temperature-compensated capability. Through a bridge wedge prism (BWP) design featuring a small incident angle and dual resonance, this platform forms two near-infrared sensing regions achieving high sensitivity at 13500.00 and 46766.67 nm/RIU, respectively. An integrated thermoelectric cooler is also employed to precisely regulate the biosensing platform's temperature, meeting the constant-temperature requirements of 37-55 degrees C for IAT. To address temperature drift in high-sensitivity applications, a matrix effectively is implemented for temperature compensation. The utilization of this platform for the quantitative analysis of synthetic human immunodeficiency virus (HIV) single-stranded deoxyribonucleic acid (ssDNA) via recombinase polymerase amplification (RPA) facilitated the detection across diverse amplification durations and sample concentrations. Furthermore, nucleic acid probe binding enables evaluation of amplicon specificity, providing a highly promising platform for advancing label-free nucleic acid amplification and real-time detection technologies.

ABSTRACT The photothermal properties of diamond nitrogen‐vacancy (NV) centers enable simultaneous fluorescence emission and localized heating, yet conventional free‐space quantum systems suffer from limited photothermal efficiency (typically<4°C/mW) and inadequate microwave integration (large in size). We developed a miniaturized quantum photothermal fiber probe utilizing a novel metal/polymer/glass composite optoelectronic fiber that simultaneously guides both lightwave and microwave radiation (at GHz). By integrating a micron‐scale diamond at the fiber tip, the probe achieves enhanced photothermal conversion (13°C/mW, 25°C–120°C range) while providing real‐time self‐monitoring through temperature‐dependent zero‐field splitting measurements with 0.2°C thermal resolution at the micrometer scale. This mass‐producible platform represents a new class of biocompatible quantum sensors combining high thermal efficiency and precise temperature feedback, as demonstrated by successful promotion of in vivo spinal cord injury repair through controlled thermal stimulation.

Surface plasmon resonance (SPR) technology is pivotal for label-free biomolecular detection but suffers from low throughput, narrow dynamic range, and insufficient sensitivity, limiting its use in high-throughput scenarios like medical diagnosis and drug screening. To address these issues, we propose a polarization-controlled intensity-modulated SPR imaging (SPRi) system integrating a 12-channel microfluidic chip and CMOS imaging technology. Its core mechanism leverages the SPR-induced phase difference between s-polarized and p-polarized light: p-polarized light excites surface plasmons for an additional phase shift, while s-polarized light remains unaffected, producing elliptically polarized reflected light. By precisely adjusting optical components and using Jones matrix modeling, refractive index changes are converted into multi-level amplified signals of phase, polarization state, and light intensity. Experimental results show a refractive index sensitivity of 24,300 a.u./RIU (linear range: 1.337–1.370 RIU), a resolution of 9.96×10⁻⁷ RIU (dynamic range: 1.331–1.410 RIU), and a baseline drift of 0.63 RU/min. Real-time self-reference suppresses noise (RMS = 0.0242). Biomolecular experiments confirm a sensitivity of 0.06586 a.u.·mL/μg for mouse IgG and a detection limit of 1.56 pg/mL for D-biotin, offering a powerful platform for biomedicine, environmental monitoring, and drug research.

Fiber-optic quantum magnetic sensors based on nitrogen-vacancy (NV) centers in diamond offer unique advantages, such as flexible optical path design and high integration, significantly enhancing their potentials for practical deployment. However, existing fiber-based NV magnetometer systems predominantly rely on bulky discrete components and relatively low sensitivity, imposing critical constraints on system miniaturization and field applicability. Here, we report a fully portable all-fiber quantum magnetometer achieving high sensitivity through three compact modules: a sensor probe integrating a conical fiber tip with micrometer-scale diamond structures sandwiched between paired pyramidal magnetic flux concentrators (PMFCs); a control module combining optical and signal processing subsystems with a customized compact microwave lock-in composite module; and a power supply unit. Magnetic and optical simulations reveal synergistic optimization of magnetic concentrators and optical interfaces, providing critical insights for optimizing quantum sensor performance parameters. The integrated system occupies 21 & times;16 & times;9 cm3with 14.9 Wtotal power consumption while demonstrating a sensitivity of57.12 +/- 1.15 pT/Hz1(/2 )at 1 Hz. The physical size of the sensingprobe is 6.7 & times;4.7 & times;4.7 cm(3).. Field validations in operational elevators and moving vehicles successfully detected sub-100 nT magnetic anomalies with temporal resolution matching target kinematics. This architecture establishes a paradigm for practical NV magnetometer miniaturization, enabling deployable quantum sensing in real-world scenarios.

Nitrogen-vacancy (NV) centers in diamond exhibit magnetic-field-sensitive quantum properties and possess four distinct crystallographic orientations, establishing a robust foundation for vector magnetic sensing. However, NV-based vector magnetic field sensors are plagued by high demodulation complexity and cost arising from cross-talk among NV orientations, in addition to the challenge of limited sensitivity. Here, we present a diamond NV fiber-optic planar vector magnetometer that enables direct readout of magnetic components with high sensitivity. This is achieved through a novel alignment scheme based on the NV centers intrinsic orientations, which suppresses cross-talk to below 2%. Meanwhile, a magneto-optically co-enhanced strategy is implemented by integrating two pairs of magnetic flux concentrators and optimizing the polarization of excitation light, leading to a nearly 20-fold improvement in sensitivity. Furthermore, the real-time readout capability and overall performance are experimentally validated under dynamic magnetic field variations in realistic scenarios. Our work provides a viable solution for high-performance NV-based vector magnetometry with simplified demodulation, facilitating its application in areas such as magnetic anomaly detection.

Exceptional points (EPs) offer significant promise for metrology via enhanced sensing, and electronic resonators have recently emerged as key platforms for EP generation due to their compactness and cost-effective components. However, an electronic resonator supports one eigenmode and thus struggles to adopt the optical platform's strategy for two-dimensional EP expansion, limiting robustness against fabrication flaws and environmental fluctuations. We introduce an approach to achieve robust EPs within a single electronic resonator. Specifically, by injecting a stabilized sinusoidal signal, the four-wave mixing mechanism inside the resonator generates a synthesized mode with the inherent mode, and these two modes form an anti-parity-time symmetry. This approach eliminates the physical inter-resonator coupling and reduces the number of resonators (the degree of freedom for EP generation), resulting in robust EP generation. Benefiting from the robust arrangement, a pronounced nonlinear feature leads to more than 40 branches of EP2 degeneracy lifting (achieving more than 20fold sensitivity enhancement relative to conventional EP sensors) and enables the first observation of chiral spectra as a unique EP degeneracy fingerprint. More critically, this approach offers a digitally controlled EP, offering real-time and continuous tuning of coupling strength. Benefiting from the tuning property, a 6-dB SNR improvement is achieved through stochastic resonance. This architecture facilitates a robust platform for EPbased sensing, unlocking opportunities to exploit EP functionalities.

Detection of single molecules is a critical aspect of biochemistry, playing a vital role in understanding molecular interactions and functions. Surface plasmon resonance (SPR) biosensors are increasingly used for this purpose due to their ability to enable label-free and rapid monitoring. However, detecting low-concentration analytes down to the single-molecule level presents a substantial challenge for SPR sensors. This work introduces a multi-objective optimization strategy to enhance the performance of label-free SPR biosensors by improving various sensing metrics, including sensitivity, figure of merit, and depth of resonant dip. These enhancements lead to a significant improvement in the single-molecule detection capabilities of SPR sensors. Additionally, the k-means clustering method is applied to identify appropriate design parameters from the optimized parameter set, thereby mitigating the effects of processing errors on sensor performance. The developed SPR single molecule biosensor has demonstrated significant improvements in refractive index S, FOM, and DFOM, with increments of 230.22 %, 110.94 %, and 90.85 %, respectively. The optimized device was tested using mouse IgG to validate the improved sensing performance. Experimental findings indicate that this approach achieves a bulk refractive index sensitivity of 24,482.86 nm/RIU, a broad linear dynamic range from femtograms per milliliter (fg/mL) to micrograms per milliliter (μg/mL), and a detection limit as low as 54 ag/mL (0.36 aM). The multi-objective particle swarm optimization method proposed herein offers an efficient, rapid, and straightforward optimization strategy for SPR biosensors, facilitating ultra-sensitive single molecule detection with low limits of detection (LOD).

A high-performance surface plasmon resonance (SPR) fiber sensor is proposed with hyperbolic metamaterials (HMMs), nano-diamond (NDs), and polydimethylsiloxane (PDMS) to enhance the temperature sensitivity and response speed. The HMM with tunable dispersion can break through the structural limitations of optical fiber to improve the refractive index (RI) sensitivity, while NDs and PDMS with large thermo-optic coefficients enable to induce significant RI change under varied thermal fields. The ternary composite endows the sensor with high-temperature sensitivity of -9.021 nm/degrees C, which is 28.6 times higher than that of the conventional gold film-based SPR sensor. Furthermore, NDs with high thermal conductivity (2200 W/mK) effectively expedite the thermal response of PDMS, which reduces the response time from 80 to 6 s. It is believed that the proposed sensors with high sensitivity, fast response time, and compact size have great potential for applications in industrial production, healthcare, environmental monitoring, etc.

Eigenmode expansion (EME) is a widely used method for modeling the electromagnetic wave propagation in multimode waveguides, where it breaks down signals into local eigenmodes and calculates them independently. Nevertheless, this methodology may challenge the causality mandated by the theory of special relativity, thus potentially disrupting the cause-and-effect relationship. This study experimentally explored light transmission in the multimode coreless fiber and found discrepancies between the EME method and measurement. To reconcile these inconsistencies, we introduced a light cone model, providing an alternative interpretation guided by the principles of special relativity. Remarkably, this innovative model did not merely resolve the observed discrepancies between the theory and experiments, but also presented a pioneering technique for designing microbend sensors. Through experimentation, we achieved the remarkable sensitivity of 500 dB/m−1 at a bending curvature of 0 m−1. Our research advances the understanding of multimode systems and paves the way for innovative sensing and communications applications in compact devices.

A magneto-optical surface plasmon resonance (MOSPR) sensor with an elevated figure of merit (FOM) is proposed. This sensor incorporates magnetophotonic crystals (MPC) and hyperbolic metamaterials (HMM) to optimize its performance characteristics. MPC and HMM respectively serve to decrease the full width at half maximum (FWHM) and amplify the sensor's sensitivity. By successfully resolving the key challenge of matching the resonant wavelength of HMM with the central wavelength of MPC using the hypersurface, the MOSPR sensor demonstrates the realization of a transverse magneto-optical Kerr effect (TMOKE) spectrum. The implementation of magneto-optical effect in wavevector dual modulation mode, along with the integration of HMM and MPC, enables the MOSPR sensor to achieve an FOM of the order of magnitude of 103 RIU- 1. This significant enhancement in performance marks a noteworthy improvement in comparison to conventional SPR sensors. This study provides a design strategy for the contactless modulation of high-performance SPR sensors, which are expected to be widely used in biomedical, environmental monitoring and chemical sensing applications.

Optical-fiber-based surface plasmon resonance (SPR) biosensors, featuring label-free, high integration, and small size, have aroused great interest in recent years. However, the reported sensors always presented with a length of several millimeters even longer, and faced a huge task in sensitivity improvement. In this study, a dual-mechanism enhanced miniature optical fiber SPR bio-probe based on nanodiamonds (NDs) is proposed and demonstrated. The probe is composed of a multimode fiber terminated by a short section of no-core fiber, whose surface is deposited with a gold film. Then, carboxylated NDs are exploited to improve the probe sensitivity simultaneously from two aspects, namely plasmonic and biological aspects. On the one hand, the plasmonic sensing field is enhanced by chemically-modifying NDs on the gold surface, which generates 46.5% improvement in bulk refractive index sensitivity. On the other hand, NDs are chemically-bonded with second antibodies to further improve the biological signal using sandwich method. As a result, the sensitivity of probe to the immunodetection of biological protein (mouse immunoglobulin G in this work) is significantly improved by more than an order of magnitude. Besides, test results prove a good specificity and the capability of working in serum environment for the probe. Our work first demonstrates the NDs application as a gain medium in the second signal amplification of SPR biosensing. Meanwhile, the obtained miniature and high sensitivity bio-probe is very suitable for the case requiring a tiny probe size or sample volume.

Optical microcavities have attracted increasing attention for high-performance sensing, where a laser scans the resonance, providing high-resolution and time-sensitive measurements. However, rapid resonance scanning can lead to readout distortions, affecting the accuracy of high-speed sensing. Traditional methods have attempted to alleviate this distortion by examining the relationship between the ringing behavior and the scanning speed or by reconstructing the steady-state spectra. Yet the complexity of distorted readouts often obscures their correlation with well-established steady-state spectra, presenting a significant challenge for transient sensing. In this study, we revisit electromagnetic theory in microcavities and discover that ringing distortion stems from quadratic phase interference between light emitted from the microcavity and the input. Remarkably, this quadratic phase solely arises from the spectral scanning speed, indicating a universality across microcavity types. As a result, the proposed method enables the recovery of a complex steady-state spectrum from a distorted readout at an arbitrary scanning speed after compensating for the introduced phases. This method bridges the gap between transient and steady-state spectra by harnessing the dimensions of spectral scanning speed, offering a promising avenue for high-speed sensing, precision measurement, and advanced scientific research.

We present a dual-mechanism nanodiamond-enhanced miniature fiber SPR probe. Its synergistic plasmonic/biological enhancement achieves order-of-magnitude sensitivity improvement in mouse IgG immunodetection for ultrasensitive trace-sample biosensing.

This study reveals eigenmode expansion (EME) challenges causality in multimode waveguides. A light cone model reconciles theory-experiment discrepancies and enables a high-sensitivity microbend sensor (500 dB/m⁻¹).

As transparent electrodes, patterned silver nanowire (AgNW) networks suffer from noticeable pattern visibility, which is an unsettled issue for practical applications such as display. Here, we introduce a Gibbs-Thomson effect (GTE)-based patterning method to effectively reduce pattern visibility. Unlike conventional top-down and bottom-up strategies that rely on selective etching, removal, or deposition of AgNWs, our approach focuses on fragmenting nanowires primarily at the junctions through the GTE. This is realized by modifying AgNWs with a compound of diphenyliodonium nitrate and silver nitrate, which aggregates into nanoparticles at the junctions of AgNWs. These nanoparticles can boost the fragmentation of nanowires at the junctions under an ultralow temperature (75 °C), allow pattern transfer through a photolithographic masking operation, and enhance plasmonic welding during UV exposure. The resultant patterned electrodes have trivial differences in transmittance (ΔT = 1.4%) and haze (ΔH = 0.3%) between conductive and insulative regions, with high-resolution patterning size down to 10 μm. To demonstrate the practicality of this novel method, we constructed a highly transparent, optoelectrical interactive tactile e-skin using the patterned AgNW electrodes.

Exceptional points (EPs) are promising for high-sensitivity sensing due to their unique square-root response to perturbations. Nevertheless, conventional EP sensors suffer from a rapid decay in sensitivity under large perturbations, restricting their practical application. This work proposes a reconfigurable EP sensing scheme based on the four-wave mixing (FWM) mechanism in a circuit. By dynamically tuning the external FWM injection, we recover the system anti-parity-time symmetry and the EP after various bifurcations. Experimental results demonstrate that the reconfigured EP exhibits enhanced sensitivity over a broad range of axial displacement perturbations between the sensor and the magnet target, extending up to 600 mu m. The achieved sensitivity is up to over 3.5 times higher than that of the fixed-EP scenario, demonstrating distinct advantages for long-range measurement. This study represents a significant step toward next-generation adaptive high-precision sensors.

As an important branch of the optical fiber sensing field,optical fiber magnetic field sensors have demonstrated significant application value in various fields owing to their advantages such as small size,remote measurement capability,and easy integration.Their development is closely related to magneto-optical materials.This study focuses on two types of typical magneto-optical materials in recent years:magnetic fluids in the classical field and nitrogen-vacancy centers in diamond in the quantum field.It reviews their research progress in optical fiber magnetic field sensors from the aspects of sensing principles,demodulation methods,structural design,and sensing applications.Finally,the current key challenges are analyzed,and the future research directions and application prospects are prospected.

Mimicking animal skin is an effective strategy for enhancing the performance of artificial skin. Inspired by a chameleon's iridophore and a spider's slit organ, a novel photonic-electronic skin (PE-skin) with excellent optical/electrical dual-sensing performance was developed by integrating a photonic crystal (PC) with a conductive MXene/silver nanowire (AgNW) composite into adhesive polydimethylsiloxane. The PC layer containing in-plane-spaced and interplane-packed nanoparticle arrays was fabricated via a fast, facile, combined method of "Marangoni self-assembly", "plasma etching", and "adhesive PDMS transfer". Notably, the PC exhibited a red-shift mechanochromic response through in-plane stretching, which is the first report of sharing the same mechanochromic behavior as a chameleon iridophore. The underlying MXene layer formed slit-organ-like cracks that provided high sensitivity, whereas the AgNWs maintained their conductivity under large strains. The resultant PE-skin exhibited a high mechanochromic sensitivity (2.57 nm %-1) and a high electrical gauge factor of 2600 in a large strain-sensing range (up to 85%). These advantages have been confirmed in the detection of full-range human motions, such as speech recognition, using a deep neural network algorithm. The red-shift stretchable PC demonstrates a new paradigm for artificial chameleon skins, and the bionic PC crack bilayer structure extends the design concept for visually interactive e-skins.