Xuhui Zhang

Tamm plasmon polariton (TPP) multilayer nanofilms have drawn significant interest for their strong light field localization enhancement and fabrication scalability, yet conventional one-dimensional geometric configurations restrict the degrees of freedom for light field manipulation. Herein, we propose a synthetic-dimensions-engineered fiber-optic TPP (S-FOTPP) sensing metatip, which enables flexible control over the resonance and sensing characteristics of the TPP in a physically constrained two-dimensional parameter space, surpassing the limits of conventional structural optimization. When the TPP resonance in the synthetic-dimensions space approaches twice the Bragg wavelength, corresponding to the characteristic optical scale of the supercell, the mode is driven into a phase-sensitive regime in which hydrogenation-induced phase perturbations in the Pd layer are converted more efficiently into measurable wavelength shifts. As a result, the H₂ sensing sensitivity is significantly enhanced compared with conventional TPP and FP structures, with a limit of detection (LOD) at the ppm level. Meanwhile, by leveraging the photocatalytic effect to regulate the reaction kinetics, the response and recovery time of the H₂-sensitive system are optimized to 7.7 and 8.8 s. Additionally, the relative contributions of the thermal and nonthermal effects in the photocatalysis process are analyzed by investigating the dependence of the response and recovery time of S-FOTPP metatips with different Pd thicknesses on the pump laser power. This work presents a metatip that integrates high sensitivity from synthetic-dimensions engineering, rapid response from photocatalytic effects, and scalable fabrication via thin-film deposition, while highlighting the potential of photocatalysis for further improving photonic device performance.

Hydrogen, a promising clean energy carrier, needs safe detection due to its flammability. Conventional electrical hydrogen sensors have drawbacks like high operating temperatures, poor selectivity and ignition risks. We propose an optical sensor using long-period fiber gratings (LPGs) coated with Pt-SiO₂ nanomaterials. It works via catalytic reaction: H₂ reacts with O₂ on Pt nanoparticles, releasing heat that shifts LPG’s resonant wavelength. Structural characterization showed porous SiO₂ with uniform Pt, ensuring efficiency and stability. Experiments proved it sensitively responds to 0.5–2.5% H₂ (max wavelength shift 7.544 nm), with fast response/recovery, good repeatability/reversibility. Logistic fitting (R² = 0.999) confirmed strong correlation. This sensor, safe, sensitive and stable, has great potential for real-time H₂ monitoring in critical environments.

To achieve high-sensitivity and intrinsically safe monitoring of hydrogen energy systems, a multi-wavelength fiber Bragg grating sensor based on the hydrogen-induced exothermic effect of Pt/WO₃ nanomaterials was designed. This structure takes advantage of the catalytic effect of Pt on hydrogen molecules to trigger a thermal effect in a hydrogen environment, resulting in a redshift in the grating’s reflected wavelength. Experiments show that the sensor has a good linear response (R² > 0.98) within a hydrogen concentration range of 0.5% to 3.5%, with stable and repeatable response and recovery processes. The multi-channel fiber structure enables synchronous detection of different central wavelengths, significantly enhancing the system’s scalability and distributed measurement capabilities. The research results indicate that this method has potential application value in hydrogen energy safety monitoring and intelligent sensor networks.

In response to the demand for hydrogen safety monitoring, this study proposes an optical hydrogen sensor based on surface plasmon resonance enhancement. Traditional palladium film optical sensors have problems such as weak response and susceptibility to interference. This design innovatively uses low refractive index magnesium fluoride as the substrate and combines it with a periodic palladium nanopore array structure. Finite-difference time-domain simulation shows that the structure exhibits a significant redshift in the reflection spectrum after hydrogen adsorption and an increase in reflectivity, with a sensitivity superior to that of traditional planar palladium films. The nanopore array enhances the optical response through local field enhancement and surface lattice resonance coupling. The magnesium fluoride substrate, with low optical loss and excellent light transmittance, further optimizes the plasmon resonance performance. This study provides a new approach for the development of highly sensitive, fast-response, and intrinsically safe hydrogen sensors.

The detection of carbon dioxide (CO₂) is important for environmental protection. This paper proposes a CO₂ sensor based on ZIF-8 functionalized evanescent wave coupled fiber Bragg grating (FBG). The sensor is constructed by coupling a multimode fiber (MMF) with a single-mode FBG, resulting in a comb - like structure spectrum and generating a strong evanescent field in the FBG region. A ZIF-8 thin film with a thickness of approximately 132 nm is coated. After ZIF-8 absorbs CO₂, its refractive index increases, the intensity of the evanescent wave in the grating region is enhanced, leading to a decrease in the effective refractive index of the optical fiber. The FBG transmission spectrum produces a sensitive blue shift, and the wavelength variation has a power - function relationship with the CO₂ concentration, thus realizing CO₂ detection. A rapid detection method is proposed, which can quickly determine within 20 seconds in the range of 0–20% CO₂ concentration. In addition, the sensor has good selectivity for CO₂; when applied to automobile exhaust detection, it accurately judges that the CO₂ concentration in the exhaust of a 15-year-old car exceeds the standard, while the other vehicles meet the standard.The sensor has the advantages of high sensitivity, fast response and simple preparation, providing an effective solution for the rapid monitoring of CO₂ in automobile exhaust and the environment.

Since high efficiency and zero-carbon emission, hydrogen, as a clean energy carrier, is potentially an alternative fuel. Unfortunately, hydrogen is a gas with a high diffusion coefficient, wide explosion limit, and low ignition energy. Thus, to ensure the safe use of hydrogen, accurate and rapid monitoring of hydrogen leakage and abnormal concentration change must be addressed immediately, which is a critical scientific and technical problem. Therefore, we propose an optics-mechanics coupling fiber hydrogen sensor without electricity-related hazard factors. This proposed fiber hydrogen sensor is constructed by combining optics-mechanics coupling, specific adsorption of hydrogen to the surface of palladium (Pd), and Fabry-Pérot (F-P) interference mechanism; the optics-mechanics coupling is aroused by hydrogen-induced stress in the suspended Pd film, which functions as an F-P resonator mirror and a hydrogen-sensitive material. According to this configuration and principle, we achieve efficient and high-selective hydrogen detection at room temperature. This optics-mechanics coupling-based fiber hydrogen sensor is characterized by the high sensitivity (0.397 nm/1%), extensive dynamic range (0.5%–3.5%), 8 s response time, and 16 s recovery time. Hence, as an intrinsically safe hydrogen sensor with the high sensitivity and quick response, this optics-mechanics coupling-based fiber hydrogen sensor can be widely used in the hydrogen energy industry chain for rapid and high-performance hydrogen detection.

In the current energy transition procedure, the application prospect of hydrogen as a clean energy material has attracted much attention. However, the widespread use of hydrogen is also accompanied by safety hazards, and how to detect hydrogen safely and efficiently has become a research focus. In this paper, we propose a fiber-optic hydrogen sensor based on the thermo-optic effect and nanomaterials, which combines the unique advantages of fiber-optic grating and platinum-loaded tungsten trioxide and is capable of detecting hydrogen concentration with high sensitivity. The principle of this sensor is to absorb hydrogen molecules by nanomaterials and trigger the exothermic effect, which leads to grating period change and refractive index change in the fiber, thus modulating the resonant wavelength of grating. By monitoring the wavelength drift in real time, the hydrogen concentration can be accurately detected. The experimental results show that the sensor can provide high sensitivity, fast response, wide detection range, and miniaturized design, which are suitable for hydrogen detection in complex environments. In addition, its dual-channel operational method further improves detection accuracy and environmental adaptability. This work provides technical support for safe hydrogen detection, which is suitable for hydrogen production, storage, industrial safety and environmental monitoring.

Accurate and real-time detection of hydrogen (H₂) is essential for ensuring energy security. Fiber-optic H₂ sensors are gaining attention for their integration and remote sensing capabilities. However, they face challenges, including complex fabrication processes and limited response times. Here, we propose a fiber-optic H₂ sensing tip based on Tamm plasmon polariton (TPP) resonance, consisting of a multilayer metal/dielectric Bragg reflector deposited directly on the fiber end facet, simplifying the fabrication process. The fiber-optic TPP (FOTPP) tip exhibits both TPP and multiple Fabry-Perot (FP) resonances simultaneously, with the TPP employed for highly sensitive H₂ detection. Compared to FP resonance, TPP exhibits more than twice the sensitivity under the same structural dimension without cavity geometry deformation. The excellent performance is attributed to alterations in phase-matching conditions, driven by changes in penetration depth of TPP. Furthermore, the FP mode is utilized to achieve an efficient photothermal effect to catalyze the reaction between H₂ and the FOTPP structure. Consequently, the response and recovery speeds of the FOTPP tip under resonance-enhanced photothermal assistance are improved by 6.5 and 2.1 times, respectively. Our work offers a novel strategy for developing TPP-integrated fiber-optic tips, refines the theoretical framework of photothermal-assisted detection systems, and provides clear experimental evidence.