We proposed ultrathin silicon-on-insulator cascaded microring resonators based on slot waveguides for glucose sensing. By leveraging the Vernier effect, a refractive index sensitivity of 3200 nm/RIU is achieved.

We demonstrate the successful functionalization of zinc oxide (ZnO) nanorod arrays with N3 dye, achieving ppblevel detection of acetone. The synergistic interaction between N3 dye and ZnO nanostructures significantly enhances sensor performance compared to pristine ZnO nanorod arrays. Among various N3/ZnO nanocomposites with different dye loadings and under diverse light illumination conditions, the sensor incorporating 1.65 wt% N3/ZnO exhibits excellent acetone detectability in terms of a high response (111, 100 ppm), a fast response speed (11 s), a low detection limit (200 ppb) and excellent selectivity under yellow light illumination. The outstanding acetone sensing performance can be attributed to (1) the photocatalytic oxidation of acetone at the surface of the N3/ZnO rods, (2) the low activation energy of acetone gas-sensing reaction, (3) the large surface area, efficient gas diffusion and high utilizing efficiency of light within the nanorod array architecture.

Sensitive quantitative detection of breast cancer gene synthetic sequences is crucial for related biosensing research. To address the limitations of traditional sensors for detecting ultra-low concentrations, this study developed a novel fiber-optic biosensor by combining nanomaterial sensitization with nanoparticle signal amplification strategies. A fiber optic sensor based on single-mode fiber-thin-core fiber-multimode fiber-single-mode fiber structure was fabricated and functionalized with black phosphorus (BP) nano-interface. The Au@cDNA complex was prepared by covalently immobilizing sulfhydryl-modified complementary DNA (cDNA) on the surface of gold nanoparticles (AuNPs). The complex specifically hybridized with the probe DNA (pDNA) immobilized on the surface of the sensor. The experimental results show that this sensor has a sensitivity of 0.793 nm/lgM and a detection limit of 20.27 fM in the concentration range of 100 fM to 100 nM. Specifically, the BP-functionalized sensor exhibits superior dynamic range, higher sensitivity, and lower detection limits for detecting Au@cDNA. The synergistic effect of interfacial sensitization by BP and signal amplification by AuNPs significantly enhances detection performance, providing a promising platform for ultra-sensitive biosensing applications.

Although flow-induced vibration (FIV) has been widely used for pipeline flow velocity measurement, accurate low-velocity measurement remains challenging due to the inherently weak FIV signal and strong background noise, which often leads to significant errors. This study proposes a nonintrusive pipeline flow velocity monitoring method based on hybrid feature extraction from FIV signals acquired via a fiber-optic acoustic sensor. The hybrid feature vector comprises standard deviation (SD), energy, frequency band energy (FBE), and zero-crossing rate (ZCR). Among these, the ZCR demonstrates excellent performance in predicting low flow velocity. Moreover, owing to the complementary characteristics among the different feature parameters, the average measurement error is significantly reduced across both low and high flow velocity ranges. Experimental results show that the relative error at a low flow velocity of 0.5 m/s is as low as 0.39%, and the average measurement error over a range of 0.5-4.5 m/s is reduced to 4.04%. These findings underscore the strong potential of the proposed approach for high-accuracy pipeline flow velocity monitoring in future applications.

We proposed CO2 refractive index gas sensors that utilize silicon subwavelength grating waveguides as the sensing arm of Mach-Zehnder interferometers, achieving a sensitivity of -22.72 pm/ppm with an optimized device length of ~132 μm.

This study proposes a fiber optic temperature sensor based on an exposed-core fiber (ECF) combined with polydimethylsiloxane (PDMS). Owing to the unique structure design of ECF and the high-performance of PDMS, a triple interference effect occurs within the device. Then, by employing the interrogation techniques including fast Fourier transform (FFT) and band-pass filtering, mixed interference spectra can be effectively separated in the spatial domain, and each of them can be individually applied for temperature measurement. The experimental results demonstrate that high-sensitivity (8.2 nm/degrees C) or large-range (160 degrees C) temperature measurements can be realized based on the separated interference spectra. Such an excellent performance is significantly enhanced over previously reported fiber temperature sensors. More importantly, different from the traditional methods by cascading two different sensing elements, high-sensitivity and large-range temperature measurement is achieved within a single sensor structure, significantly reducing the volume and complexity of the sensing device.

The blockage of liquid pipelines greatly affects the safe operation of pipelines, while it is rarely discussed in the previous studies. In this paper, the Fiber Bragg Grating (FBG) sensor is used to monitor the blockage state of liquid pipeline system, and the wavelength shift characteristics of FBG under different degrees of front blockage and rear blockage are discussed. The experimental results have shown that the liquid flow velocity is affected when the inner liquid pipeline is blocked, and the wavelength shifts of different FBGs show the significant differences. Specifically speaking, when the pipeline is blocked, the FBG sensor before and after the blockage point will show the opposite wavelength shifts. The FBG center wavelength shows the red-shift when it located before the blockage point, while the blue-shift occurs when it located after the blockage point. The wavelength shift range is closely related to the relative position between the FBG and the blockage point. Besides, the wavelength shift of FBG caused by rear blockage is significantly greater than that of the front blockage. Based on the above results, an effective method to detect the pipeline blockage can be summarized. These research results provide important theoretical support and technical guidance for real-time monitoring of pipeline health status and prevention of pipeline blockage.

Silicon microring resonators (MRRs) are promising for on-chip optical gas sensing due to their strong light-matter interaction, compact footprint, and mass-scalable fabrication potential. However, for refractive index sensors, it is essential to consider the cross-sensitivity to temperature induced by the thermal-optic effect in MRRs. To address this challenge, we demonstrate a silicon MRR coated with gas-sensitive polyhexamethylene biguanide hydrochloride as the upper cladding for carbon dioxide sensing. The engineered MRR exhibits distinct temperature and gas sensitivities for TE0 and TE1 modes. With the linear independent responses, a gas sensitivity of -0.90 pm/ppm within a range of 700 ppm is demonstrated in conjunction with the temperature compensation. The response and recovery times of gas sensing are measured as ∼3.5 and 1.5 min. Our study paves the way for on-chip optical gas sensing with temperature compensation.

Subwavelength grating structures are widely used in integrated optical devices due to their compact footprints and flexible refractive index tailoring. In this paper, we present a subwavelength grating (SWG) coupler for a 70nm-thick silicon waveguide without the upper cladding. The device was designed by using a particle swarm optimization algorithm in 3D finite-difference time-domain simulation. Experimental measurements show that the SWG coupler with a minimum feature size of similar to 210 nm has a peak coupling efficiency of -7.0 dB with a 1-dB bandwidth of similar to 40 nm and a backreflection of similar to-18.7 dB at 1550 nm wavelengths for transverse-electric polarized light. The ultrathin device structure is simple and reproducible, making it well suited for sensing and optoelectronic integration applications at low cost. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

A fiber-optic DNA biosensor with temperature compensation for the specific detection of label-free deafness gene is proposed and demonstrated. The biosensor is fabricated by splicing a section of exposed-core microstructure fiber (ECF) between two single-mode fibers (SMFs) to form an optical fiber microcavity Fabry-Perot interferometer (FPI). The ECF eliminates the temperature cross-sensitivity and improves the sensitivity of the sensor. In this study, a sensitive film layer is prepared by coating poly-L-lysine (PLL) on the surface of the sensor. The probe DNA (pDNA) is immobilized on the surface by layer-by-layer assembly. The sensor can detect local refractive index (RI) changes that occur on the surface of the fiber due to the specific binding of complementary DNA (cDNA) to pDNA. Therefore, the sensor can achieve high sensitivity and high selectivity detection of cDNA. Experimental results show that the sensor can detect cDNA concentrations as low as 1 mu M by demodulating the phase change of the interference spectrum. The proposed fiber-optic DNA biosensor has the ability to label free, selective, and real-time detection, and has broad application prospects in the fields of medical diagnosis, cancer screening, and environmental science.

We present the design and characterization of grating couplers for 70 nm-thick silicon waveguides at 2-µm wave band, demonstrating a peak coupling efficiency of -8.7 dB and a 1 dB bandwidth of 60 nm.

A fiber-optic biosensor based on self-reference parallel Fabry-Perot interference (FPI) is proposed for label-free DNA detection. The parallel FPI is formed by fusing a section of exposed core fiber (ECF) in SMF and MMF. Adopting the air cavity of the ECF as a reference, a self-reference differential phase demodulation technique is designed to improve the stability and resolution of the demodulation system. By functionalizing the fiber surface, the sensor can efficiently capture complementary DNA (cDNA). In addition, the specific selection performance of the sensor is explored using non-complementary DNA (N-cDNA). The experimental results show that the sensor exhibits a good linear response in the concentration range of 1 to 5 µM, and the sensitivity reaches 5.53°/µM. The detection concentration can be as low as 1 µM. The proposed fiber-optic DNA biosensor has good sensitivity and selectivity and has broad prospects in the fields of biomedical diagnostics, environmental monitoring, and food safety detection.

Triethylamine (TEA) is a kind of flammable and pungent gas, which extensively exists in our daily life. It is paramount important to monitor ppb-level TEA rapidly and selectively at low temperatures. Herein, tungsten oxide hollow microspheres were successfully co-modified by different amount of Pd and N719, and were used to construct semiconductor gas sensor. TEA sensing properties were tested for the N719-Pd/WO3 and Pd/WO3 composites under various light illumination conditions. It is exciting to observe that the 0.3 wt% N719-Pd/WO3 sensor exhibits excellent TEA detectability in terms of ultra-high response (1410, 50 ppm), low operating temperature (100 degrees C), fast response speed (25 s) and low detection limit (27 ppb) under white light illumination, which are superior to WO3 sensors loaded with other Pd and N719 concentration as well as upon other light illumination conditions. This excellent sensing performance indicates that the proposed dual-effect improved sensitization by combining noble metal functionalization with visible light excitation offers an effective design for highly sensitive and efficient gas sensors based on wide-band gap semiconductors.

Although fiber-optic distributed acoustic sensing (DAS) has been widely applied for intrusion recognition in the perimeter security field, challenges still remain for high-accuracy recognition of new types of intrusion events. Drone, as a non-contact, stealthy intrusion event, has not been reported to achieve effective monitoring and recognition by employing the fiber-optic DAS technology. By introducing drone intrusion, the scope of the threatening intrusion in the perimeter security monitoring field is extended. This study proposes a multi-source threatening event recognition scheme targeting drone intrusion in the fiber optic DAS system. To achieve this objective, a dual-stage recognition method is proposed. Besides, the wavelet denoising method is applied to extract the effective signal from weak disturbances introduced by drone flight. The variational mode decomposition (VMD)-based hybrid feature vector is formed to remove the noise and further extract the effective signal characteristics. Next, we demonstrate a hybrid model framework based on convolutional neural network (CNN)+long short term memory (LSTM)+self-attention mechanism to achieve the effective recognition of multi-source threatening event targeting drone intrusion. Particularly, we thoroughly discuss the distinguishing ability between drone intrusion and non-threatening wind blowing, and the recognition ability for the simultaneous occurrence of both human-contact intrusion and non-contact drone intrusion. The experimental results show that, the proposed recognition scheme can effectively distinguish the drone intrusion from the non-threatening wind blowing event with a high accuracy of 100%. In addition, when drone intrusion, environmental disturbances and human-contact intrusion occur simultaneously, a high recognition accuracy of 96.25% is achieved with a fast response time of 0.733 s.

We proposed dual microring resonators with SiO2 and polyhexamethylene biguanide hydrochloride claddings for CO2 sensing with temperature compensation, achieving a simulated sensitivity of 3.6 pm/ppm. Then we fabricated dual microrings and conducted temperature-response measurements.

Optical bistability can be used to explore key components of all-optical information processing systems,such as optical switches and optical random memories.The hybrid integration of emerged two-dimensional layered PtSe2 with waveguides is promising for the applications.We demonstrated the optical bistability in the PtSe2-on-silicon nitride microring resonator induced by a thermo-optic effect.The fabricated device has a resonance-increasing rate of 6.8 pm/mW with increasing optical power.We also established a theoretical model to explain the observation and analyze the device's performance.The study is expected to provide a new scheme for realizing all-optical logic devices in next-generation information processing systems.

In this paper, a temperature insensitive wide-dynamic-range distributed strain sensor with centimeter-level spatial resolution based on optical frequency domain reflection technology is proposed. It adopts a polarization-maintaining photonic crystal fiber as the sensing fiber, and experimental results demonstrate that its temperature sensitivity is much smaller than that of the standard polarization-maintaining fiber. Benefited from the specially designed cross-correlation algorithm, the sensor achieves the maximum measurable strain reaches 7000 mu & varepsilon; with spatial resolution of 1.66 cm. This provides a new approach to address current issues with special fiber sensors, such as single-point sensing and low spatial resolution, which shows great significance for structural health monitoring of buildings, bridges and tunnels with urgent requirement of large dynamic range.

On-chip refractive index (RI) sensors, which use resonant shifts of micro-cavities to detect environment change, have the advantages of high sensitivity, real-time detection, and compact footprints. However, the crosssensitivity of the temperature variation severely interferes with sensing results. In this paper, we present a dual-mode microring resonator (MRR) with a cladding layer of polyhexamethylene biguanide hydrochloride (PHMB) for relative humidity (RH) sensing to overcome the limitation. Specifically, the influences of the RHinduced RI change of the PHMB cladding and temperature variations on the effective RIs of TE0 and TE1 modes can be decoupled based on the transmission spectral measurements. Using this method, we have demonstrated the temperature-compensated RH sensing which achieved a maximum sensitivity of -54.7 pm/% RH and a limit of detection of 0.8 %RH under the room temperature condition. Besides, a computational model based on the sensing response of the device was proposed and verified, which demonstrated that the structure can accurately measure changes in RH and temperature simultaneously. Our methodology has the potential to become a new reference for developing on-chip RI sensors with temperature compensation.

We proposed an ultrathin silicon loop mirror reflector for enhancing the PtSe 2 -on-waveguide optical absorption. Simulations show that the absorption coefficient of the device is 4.9 times that of a conventional 220 nm-thick silicon strip waveguide.