An ultra-compact Fabry-Perot (FP) interferometer integrating a microbubble with polydimethylsiloxane (PDMS) end-cap is fabricated with physical wrapping and fusion splicing methods for sensing ambient temperature. The mechanically robust polymer cap has an average diameter of 0.5 cm. The end-capped sensor exhibits a high temperature sensitivity of -6.818 & times; 10- 2 dB/degrees C, which is 10 times higher than that of the sensor composed of only microbubble without PDMS encapsulation. Due to its simple fabrication technique, high sensitivity, fast response, and good stability, the temperature sensor has significant potential in the bio-pharmaceutical, chemical, and environmental industries.

A high-sensitivity fiber-optic micro-strain sensor based on a parallel Fabry-Perot interferometer (FPI) and the optical Vernier effect is designed, fabricated, and demonstrated. The sensor comprises two parallel FPIs. The sensing interferometer (SI) employs a unique cantilever-beam bubble microcavity structure, achieving a high strain sensitivity of 32.89 pm/mu epsilon, while the reference interferometer (RI) is detached from the experimental environment. By connecting them in parallel, the optical Vernier effect further enhances the strain sensitivity to 555 pm/mu epsilon, representing an amplification factor of approximately a factor of 17. Meanwhile, the sensor exhibits low temperature cross-sensitivity of approximately 9.73 mu epsilon /degrees C. The sensor, with its compact structure, simple fabrication, and low cost, has broad application prospects in fields such as the safety monitoring of oil and gas transportation pipelines.

This paper proposes an ultra-low-loss hollow-core anti-resonant fiber (HC-ARF) operating in the near-infrared band. The designed HC-ARF adopts double-layer hybrid nested cladding tubes. The finite element method is used to analyze the influence of the cladding tube structure on transmission loss. The results indicate that the ultra-low confinement loss of less than 9.31 & times; 10-7dB/m is achieved in the range of 1.48-1.95 & micro;m. At 1.55 & micro;m, the confinement loss drops to 1.58 & times; 10-7dB/m. In addition, this fiber exhibits excellent bending resistance. At a bending radius of 10 cm, the bending loss is only 4.48 & times; 10-4 dB/m. At the same time, the bending loss can be kept below 4.08 & times; 10-4 dB/m as the bending radius is larger than 35 cm. The structure provides a novel approach, to our knowledge, for designing HC-ARFs with low loss and exhibits broad application prospects in long-distance fiber optic communication systems. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

A D-shaped photonic quasi-crystal fiber (PQF) surface plasmon resonance (SPR) sensor is numerically designed and analyzed. By patterning a silver-titanium dioxide (Ag-TiO2) composite film into a grating structure, the localized surface plasmon resonance (LSPR) is enhanced and the full width at half-maximum (FWHM) is narrowed. The finite element method (FEM) is employed to optimize the structural parameters. In the refractive index (RI) range of 1.36-1.425, the sensor obtained a wavelength sensitivity of 15,800 nm/RIU and a maximum figure of merit (FOM) of 929.02RIU-1. A maximum amplitude sensitivity (AS) of 11,709.8RIU-1 is also obtained. With its excellent FOM and AS, the proposed sensor holds great application potential in chemistry, biomedicine, and environmental monitoring. These results demonstrate a promising strategy for designing high-performance SPR RI sensors.

A single-ended ultracompact reflection-type compound-cavity temperature sensor based on the Fabry-Perot (F-P) interferometer, formed by integrating a microbubble with a cavity derived from a polydimethylsiloxane (PDMS) coating, is designed and analyzed. The sensor probe features a temperature-sensitive PDMS forming a mechanically robust polymer cap with an average diameter of only 300 mu m, endowing the device with ultracompact dimensions for temperature detection in a confined space. Within the operating temperature range of 30 degrees C to 80 degrees C, the sensor achieves a temperature sensitivity of 7.18 pm/degrees C based on fine spectral measurements. Moreover, the proposed device exhibits negligible pressure sensitivity at sub-atmospheric pressures, effectively eliminating the pressure cross-sensitivity observed in conventional F-P temperature sensors. This temperature sensor has significant potential for applications in sub-atmospheric environments, including medical wearable devices, aerospace engineering, and the bio-pharmaceutical industry.

Subsurface intrinsic attenuation produces poorly illuminated images with reduced resolution. Two-way normalized Q-compensated reverse-time migration (Q-RTM) that uses viscoacoustic wavefields in a normalization-based compensation framework can provide stable and effective energy recovery, but the strong high-frequency loss inherent to viscoacoustic wavefields limits achievable resolution. To mitigate this limitation, we propose an improved two-way normalized Q-compensated reverse-time migration that employs a dual high-frequency enhancement mechanism. First, we introduce a dispersion-only wavefield possessing a broader frequency bandwidth and use it to construct a revised two-way normalization compensation scheme; this step preliminarily boosts effective high-wavenumber components while preserving numerical stability. Second, we derive a stable wavenumber-dependent compensation operator from the constant-order decoupled fractional Laplacian (DFL) viscoacoustic wave equation and embed it into the normalization scheme, providing a secondary high-frequency enhancement with intrinsic suppression of time-accumulating instabilities. By applying more comprehensive high-wavenumber compensation, the proposed method significantly improves imaging resolution. Numerical experiments on synthetic models and a field dataset demonstrate that our approach achieves effective energy compensation and superior resolution compared with conventional two-way normalized Q-RTM.

An adaptive machine learning-enhanced plasmonic sensing system with high sensitivity and intelligent functionality is designed and demonstrated for water quality and safety monitoring. The system consists of a microstructured optical fiber (MOF) sensor based on the surface plasmon resonance (SPR) effect. The sensor incorporates four large air holes and two symmetrically arranged micro-grooves, the latter embedded with gold nanowires at their base. The sensor can detect analyte refractive indexes (RI) between 1.33 and 1.40 accurately. Furthermore, an artificial neural network (ANN) is integrated into the data processing framework to predict the confinement loss (CL), independent of the imaginary part of the effective RI, with a mean square error (MSE) of only 0.004. Both the detection intelligence and prediction reliability are greatly improved. Three water pollutants, namely pathogens, heavy metal ions, and algal pollutants, are selected to demonstrate the practical potential. The sensing system shows maximum wavelength sensitivity (WS) of 24,390 nm/RIU, 15,000 nm/RIU, and 21,667 nm/RIU, resolution (R) being 4.10 x 10-6 RIU, 6.67 x 10-6 RIU, and 4.62 x 10-6 RIU, and figures of merit (FOM) being 81.51 RIU- 1, 68.64 RIU- 1, and 70.91 RIU- 1, respectively. Boasting a simple structure and excellent properties, the system can be used for real-time and simultaneous monitoring of multiple water contaminants and supports automatic optimization of key sensing parameters. It offers a highly sensitive and intelligent integrated technical solution for safety monitoring in complex water environments.

A terahertz-band single-polarization (SP) hollow-core anti-resonant fiber (HC-ARF) based on asymmetric cladding structures is proposed. In the Y axis direction, the mixed nested structure based on circular and elliptical tubes is used to suppress the loss of the Y-polarized fundamental mode (YPFM). The X axis cladding structure is composed of an outer circular tube with gradient wall thickness and two inner circular tubes which can enhance the transmission loss of the X-polarized fundamental mode (XPFM). The numerical analysis results demonstrate that the losses of XPFM and YPFM are 1.05 dB/m and 3.1 & times; 10(-5) dB/m, respectively, at 1 THz. The ultra-high polarization loss ratio (PLR) of 33 727 is achieved. Meanwhile, the PLR can be maintained greater than 100 in the range of 0.96-1.04 THz and 1.115-1.125 THz. The excellent performance of the designed HC-ARF further expands its application potential in the terahertz-band.

A microstructured optical fiber (MOF) sensor based on surface plasmon resonance (SPR) sensor is presented for the online monitoring of multiple biothreat agents. Featuring a compact design with few air holes, the sensor further incorporates two symmetric micro-grooves embedded with gold nanowires, which together form an efficient microfluidic channel to enable highly sensitive refractive index (RI) detection. The finite element method (FEM) based COMSOL Multiphysics software is employed to numerically simulate and analyze the sensing performance of the proposed sensor. The analysis reveals that the sensor supports simultaneous and precise detection of six common cancer cells and SARS-CoV-2, thereby enabling high-throughput multi-biological analysis. Within the RI range of 1.33–1.40, the sensor demonstrates maximum wavelength sensitivity (WS) and resolution (R) of 40,000 nm/RIU and 2.50 × 10− 6 RIU, respectively. In targeted cancer cell assays, it achieves a maximum WS of 36,429 nm/RIU with an R of 2.75 × 10− 6 RIU, along with a figure of merit (FOM) of 52.69 RIU− 1, a signal-to-noise ratio (SNR) of 1.75, and a detection limit (DL) of 502.36. For virus detection, it attains a maximum WS of 13,158 nm/RIU with an R of 7.5 × 10− 6 RIU. Overall, by providing an efficient and reliable platform for early disease diagnosis and timely intervention, this MOF-SPR sensor is demonstrated to hold considerable promise for both scientific research and practical applications.

Light-matter interactions provide versatile routes for probing and controlling chemical reactivity, charge transport, and material properties. Time-periodic external fields can reshape electronic states and open new dynamical pathways beyond the field-free Born-Oppenheimer (BO) picture. Floquet nonadiabatic dynamics has consequently emerged as an important framework for describing coupled electron-nuclear dynamics under periodic driving. In this Perspective, we first discuss recent developments in Floquet nonadiabatic dynamics methods for closed and open quantum systems. We then highlight how this framework provides mechanistic insights into electron transfer at molecule-metal interfaces, quantum transport in molecular junctions, carrier dynamics in crystalline solids, and multicolor Floquet engineering. Finally, we outline key conceptual and computational challenges that must be addressed to transform Floquet nonadiabatic dynamics from model-based demonstrations into predictive, first-principles simulations of realistic light-driven processes.

In this paper, an ultracompact parallel Fabry-Pérot interferometer (FPI) strain sensor is designed and experimentally evaluated. The novel sensing component consists of a tapered single-mode fiber (SMF) and a hollow capillary tube (HCT), fabricated with fusion splicing method. Leveraging the optical Vernier effect arised from the parallel configuration, the sensor exhibits a substantially enhanced strain sensitivity of 631.12 pm/µε in the range of 0-200 µε, which is 12 times higher than that of a sensor composed of sensing interferometer. It also has suppressed temperature cross-sensitivity of 0.0015 µε/°C in the range of 25-150°C, indicating high reliability in practical strain applications. Gaining the advantages of high sensitivity, good stability, and low temperature crosstalk, this axial strain sensor is anticipated to be applied as a useful platform for multi-parameter sensing scenarios.

A multi-functional optical fiber sensor based on surface plasmon resonance (SPR) is designed to simultaneously detect temperature (T), magnetic field (H), relative humidity (RH), and voltage (U). In the device, an eight-hole photonic crystal fiber (8-hole PCF) forms the substrate, and gold (Au) films are plated on the alternately distributed air holes, which are subsequently filled with polydimethylsiloxane (PDMS), magnetic fluid (MF), polyvinyl alcohol (PVA), and E7 nematic liquid crystal (E7NLC) for sensing the four different physical entities. This sensor has a simple structure and significantly improves the integration level and accuracy. Owing to these merits, the design has large application potential.

The combination of high-quality-factor (Q-factor) bound states in the continuum (BIC) and chiral metasurfaces has attracted much attention in the field of photonics. Here, we design and analyze a "sandwich" all-dielectric metasurface with two silicon cross-shaped cylinders distributed on the upper and lower surfaces of the silica. The transition from symmetry-protected BIC to chiral quasi-BIC (QBIC) is achieved by innovatively breaking both the mirror symmetry and the in-plane inversion symmetry of the structure, resulting in a transmittance-ratio circular dichroism (RCD) close to unity and a high Q-factor. In particular, three chiral QBICs (QBIC1, QBIC2, and QBIC3) are realized in the terahertz band without increasing the complexity of the structure at each layer. Multipole decomposition and near-field analysis demonstrate that QBIC1 and QBIC2 are dominated by the toroidal dipole and magnetic quadrupole, while QBIC3 is mainly affected by the electric quadrupole and magnetic quadrupole. In addition, the presence of positive and negative states due to the RCD values of the structure suggests a spin selectivity for different frequency bands. Theoretical assessment shows a maximum Q-factor of 3.94 & times; 104, a maximum sensitivity of 245 GHz per refractive index unit (RIU), and a figure of merit of 7927 RIU-1. The results reveal a novel approach for selectively modulating circularly polarized light, demonstrating significant potential in biomolecular detection, high-spectral-resolution chiral biosensors, and chemical analysis.

Addressing the challenge of coordinating mixed-frequency pump sets in multi-pump, multi-well polymer injection systems, this paper proposes an adaptive weight fusion prediction model integrating Bayesian Optimisation LightGBM (LGBM-BO) with attention mechanism gated recurrent units (GRU-CBAM). This model simultaneously captures static feature relationships and dynamic temporal dependencies, achieving high-precision prediction of plunger pump frequencies. It provides reliable technical support for the digital regulation of oilfield polymer flooding systems.

Chiral metaphotonic devices are indispensable, especially for enantioselective sensing, and inherently rely on high-quality factor resonances and strong chiroptical interactions. Specifically, enhancing optical chirality in the light fields that directly interact with chiral molecules is the fundamental prerequisite to achieving ultrasensitive chiral detection. Herein, a multilayer all-dielectric toroidal dipole Fabry-Pérot bound states in the continuum (TD FP-BIC) chiral metasurface is designed and analyzed. The TD FP-BIC chiral metasurface generates a significant near-field optical chiral density in the unstructured regions, achieving a quality factor (Q) of 6.6 × 104. Furthermore, the single-layer TD metasurface amplifies the far-field circular dichroism signal of chiral molecules by 128 times, while the TD FP-BIC chiral metasurface amplifies it by a factor of 1092. Both the maximum chiral enhancement (Cmax) and the average chiral enhancement occur in the unstructured region, with increases of 5×104-fold and 2011-fold, respectively. The results reveal a new paradigm for the design of advanced chiral metasurfaces with high-Q resonances and accessible superchiral fields, having immense potential in ultrasensitive chiral detection, on-chip sensing, and near-infrared chiral optical applications.

A highly sensitive optical fiber strain sensor with simple structure, easy preparation and temperature insensitivity is proposed. It consists of a parallel Fabry-Perot Interferometer (FPI) based on the Vernier Effect (VE). The sensing cavity (FPIS) is formed by two single-mode fibers (SMFs) by fusion splicer arc discharge, and the reference cavity (FPIR) consists of two SMFs inserted into a hollow capillary tube(HCT). The sensor has a high strain sensitivity of -42.04 pm/mu epsilon and an ultra-low temperature cross-sensitivity of 0.022 mu epsilon/degrees C, which reduces the measurement errors caused by temperature variations. At the same time, stable experimental measurements show that the interference fringes change by less than 20 pm. This sensor combines high strain sensitivity, ultralow temperature cross-sensitivity, and stable performance for precise strain measurement applications.

A temperature-insensitive Fabry-Perot interferometer (FPI) based on the Vernier effect is proposed for strain measurement. Two structurally similar FPIs are prepared with a fusion splicer, and the air cavity in the middle forms the Fabry-Perot cavity. The one FPI with a thinner wall serves as the sensing cavity, and the other is the reference cavity. The strain sensitivity of the optical fiber sensor for 0-600 mu s is 131.7 pm/mu s, which is 9 times higher than that of the single structure FPI. It has a temperature sensitivity of 2.7 pm/degrees C and a temperature cross-sensitivity of 0.021 mu s/degrees C in the temperature range between 25 and 200 degrees C. The sensor has excellent repeatability and stability in strain measurements. The results show that the strain sensor is simple, cost-effective, and easy to fabricate. In conjunction with its high sensitivity, it has great commercial potential in strain measurements, especially in complex temperature environments.

In this paper, a high-sensitivity temperature and pressure sensor is designed. It utilizes a diaphragm to transfer pressure to a double-hinged lever structure and adopts a fiber Bragg grating (FBG1) as the strain sensor to measure pressure. The introduction of the double-hinged lever effectively improves the sensor's pressure measurement sensitivity. The sensor's measuring range is 0-18 MPa and the sensitivity is 453.16 pm/MPa. At the same time, another fiber Bragg grating (FBG2) is pasted on the lever to eliminate the temperature influence in the pressure measurement process and realize the simultaneous measurement of temperature and pressure. The sensor's temperature sensitivity is 10.41 pm/degrees C in the 25-65 degrees C range. Due to their anti-electromagnetic interference characteristics, optical fiber sensors are commonly used to measure temperature and pressure in harsh environments.

A dual-parameter sensor based on a coreless optical fiber (CF) is designed for the simultaneous detection of magnetic fields (H) and temperature (T). The side of the CF is polished to form a double D-shape and etched to a certain grove depth on the side surface for gold plating and filling with the magnetic fluid (MF) and polydimethylsiloxane (PDMS). The sensor operates on the principle of surface plasmon resonance (SPR) to achieve magnetic field and temperature sensing. Finite element analysis reveals the modal characteristics of the sensor, showing that the effective magnetic field and temperature detection ranges are 31-200 Oe and 20 C-degrees-80 C-degrees, respectively. The maximum magnetic field sensitivity and temperature sensitivities are 20.207 nm/Oe and -8.423 nm/degrees C, respectively. Compared to other dual-parameter magnetic field and temperature sensors currently proposed, the magnetic field sensitivity increases by nearly two orders of magnitude, and the temperature sensitivity increases several times. The structure of photonic crystal fiber or antiresonant fiber (ARF) is complex. In contrast, this design offers a simpler structure and fabrication process. The sensor has immense potential in medical diagnosis, environmental detection, and aerospace fields.

Source-independent Q-compensated least-squares reverse time migration based on the convolutional misfit function constitutes an amplitude-preserving methodology that effectively compensates for seismic attenuation and alleviates the constraints imposed by the source wavelet. Nevertheless, its conventional implementation, which constructs the gradient through the cross-correlation between background wavefield and adjoint wavefield propagating in opposite directions, incurs exorbitant storage and computational expenses. To ease the computational and storage pressures, we developed an efficient source-independent Q-compensated scheme by introducing a local Nyquist cross-correlation imaging condition to formulate gradient. Instead of employing entire wavefields for migration, the local Nyquist cross-correlation imaging condition, in combination with the Nyquist rate, adopts only the local wavefields around the excitation amplitude time. Consequently, the proposed scheme considerably diminishes the storage requirement as well as the additional time resulting from frequent input-output operations, thereby enhancing computational efficiency. Numerical examples conducted on the 2D layered model, Marmousi model, field data, and the 3D Overthrust model reveal that the proposed scheme is capable of attaining imaging accuracy comparable to that of the conventional scheme, while exhibiting superior storage and computing performance, and possesses higher feasibility in 3D applications.