Optical microcavities combined with different materials have inspired many kinds of functional photonic devices, such as lasers, memories, and sensors. Among them, optofluidic microbubble resonators with intrinsic micro-channels and high-quality factors (high-Q) have been considered intriguing platforms for the combination with liquid materials, such as the hydrogel and liquid crystal. Here, we demonstrate a water-infiltrated hybrid optofluidic microcavity for the precise multidimensional measurement of the external laser field. The laser power can be precisely measured based on the photo-thermal conversion, while the wavelength-resolved measurement is realized with the intrinsic absorption spectrum of water. Empowered by machine learning, the laser power and wavelength are precisely decoupled with almost all predictions falling within the 99% prediction bands. The correlation coefficient R2 of the laser power and wavelength are as high as 0.999 85 and 0.999 54, respectively. This work provides a new platform for high-precision multidimensional measurement of the laser field, which can be further expanded to arbitrary band laser measurement by combining different materials.
Heavy metal ions have drawn enough attention due to their harm to both humans and environments, and there has been an urgent need for stable and quick detection of them. Besides, the manganese ion is one of the most abundant ions in urban water systems, which needs to be monitored carefully. Hereby, a carbon dots (CDs) (the microwave method) based surface plasmon resonance (SPR) Mn2+ sensor has been proposed and discussed, which could achieve high detection sensitivity of 6.383 nm/lg(ppb) in the range of 0 ppb–200 ppb on manganese ions, with the detection limit of 0.3462 ppb. The proposed sensor also possesses high stability upon time and temperature, and it also has great ion selectivity against 9 other ions. Practical usage scenarios have been tested on the human serum, tap water, lake water, and river water, which confirm that the proposed sensor holds great potential for both blood tests and environmental monitoring.
This paper proposes a continuously tunable random lasers (RLs) based on the gain system of cellulose nanocrystals (CNCs)-doped hydrogels and the laser dye made of Rhodamine B (Rh B). Between them, the prepared CNCs-doped hydrogels have not only a weak scattering structure that can provide excellent multiple scattering, thus yielding a large gain, but also good mechanical properties that can provide great advantages in the tuning of RL. The experimental results indicate that the RL emission wavelength blue shifts with an increase in the stretching length. The continuous tuning range reaches up to 7.1 nm when the CNCs-doped hydrogels are stretched to 400%. In addition, the proposed CNCs-doped hydrogels effectively solve the problem of the structures of traditional hydrogels, which are easily destroyed during repeated stretching and ensure good stability of RL output and tuning. The RL error is tested and found to be less than 0.5 nm, when the same length is stretched during repeated stretching. Our results provide a new approach to obtain tunable and stable RLs. Simultaneously, in combination with the good biocompatibility of CNCs-doped hydrogels, the proposed RLs demonstrated great importance in the biological field.
We have numerically and experimentally investigated the flow rate measurement of the pipeline based on the optical fiber. Employing the large eddy simulation (LES) model, we have quantitatively analyzed the pressure fluctuation of the pipe wall caused by the turbulent flow in the pipeline. The simulation results have shown that the standard deviation of pressure fluctuation was quadratic with the flow rate. We have verified the theoretical model by using a distributed optical fiber acoustic sensing (DAS) system in the flow rate range from 0.61 m/s to 2.42 m/s. The experimental results were consistent with the simulation results very well. Furthermore, to improve the measuring error at the low flow rate, we have employed the composite adaptive denoising algorithm to eliminate the background noise and system noise. The final results have shown that the minimum goodness of fit was improved from 0.962 to 0.997, and the variation of the quadratic coefficient significantly decreased by 93.25%. The measured flow rate difference was only 0.84% between different sensing points in repeated experiments.
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.
The upconversion (UC) phosphors in the series (100-x-y-z)Y2O3+xLa2O3+yYb2O3+zEr2O3 with x=0, 2, 4, 6, 8, and 10; y=3; z=0.1 were prepared by a combustion method to know the effect of La3+ doping on UC emission wavelengths and their intensities. The UC emission has been studied under the 980 nm (power 166 mW) and 932 nm (variable power) diode laser excitation. The phosphors show the green and red band emission pertaining to Er3+ ions. It has been observed that with a lower concentration of La3+ ions (up to 6 mol%), the emission intensity of both bands decreased, with the red band emission remaining dominant. However, as the doping concentration exceeded 6 mol%, the emission intensity of the green band increased significantly, leading to a switch from the red to green band emission at 10 mol% La3+ doping. The variation in the UC emission intensity with the pump power and temperature has been measured. The Er3+ and Yb3+ co-doped UC phosphor with 10 mol% La3+ doping can be used in optical thermometry with the maximum absolute sensitivity of 0.054 3 K−1 at 303.15 K. The cubic crystal structure of prepared samples has been confirmed by a powder X-ray diffraction study. Doping of La3+ did not change the crystal structure, but the variation in lattice parameters was witnessed due to the modification of the crystal field by the La3+ ion. The absorbance of samples over the spectral range of 200 nm–1 100 nm has been measured by the diffuse reflectance spectroscopy. All samples exhibited large band gaps. The morphology of particles has been studied by the scanning electron microscopy. Commission International de I’Eclairage (CIE) color coordinates have been determined.
Whispering gallery mode (WGM) microresonators emerged as a promising platform for highly sensitive sensing applications due to their high-quality factors and small mode volumes. They offer the advantages of the ultrahigh sensitivity and compact size, rendering them suitable across multiple fields. A stable encapsulation process is essential for practical applications to establish a reliable coupling system between the microcavity and its waveguide coupler, especially for the microtoroidal resonator and tapered fiber coupler. However, adjusting the coupling coefficient after the packaging process poses challenges, thereby compromising coupling accuracy and limiting its range of applications. It is imperative to provide a platform of tunable coupling for packaged WGM resonators. Here, we provide an approach for leveraging the magnetostrictive effect to dynamically regulate the fiber-cavity coupling, enabling the measurement of the magnetic field as an example. Moreover, we show the fine-tuning of coupling within the packaged WGM microresonator, allowing the precision control of the optomechanical effect. Through this method, a tunable coupling platform in a packaged system is realized, opening up new dimensions of research in various fields.
This work introduces a novel single-package optical sensing device for multiple gas sensing, which is suitable for breath analysis applications. It is fabricated on a coverslip substrate via a sputtering technique and uses a planar waveguide configuration with lateral incidence of light. It features three sequentially ordered strips of different materials, which serve to increase the multivariate nature of the response of the device to different gases. For the proof-of-concept, the selected materials are indium tin oxide (ITO), tin oxide (SnO2), and chromium oxide III (Cr2O3), while the selected gases are nitric oxide (NO), acetylene (C2H2), and ammonia (NH3). The sensing mechanism is based on the hyperbolic mode resonance (HMR) effect, with the first-order resonance obtained for each strip located in the near infrared region. The multivariate response of the resonances and the correlation with the concentration of each gas allow training a machine learning (ML) model based on a nonlinear autoregressive neural network, enabling the accurate prediction of the concentration of each gas. The obtained limit of detection for all the gases was in the order of a few parts per billion. This innovative approach coined as the multivariate optical resonances spectroscopy demonstrates the potential of HMR-based optical sensors in combination with ML techniques for ultra-sensitive multi-gas detection applications using a single device.
The work describes a surface plasmon resonance (SPR) sensor that measures the liquid level and refractive index (RI) simultaneously. The sensor is fabricated by a polymer optical fiber (POF) with a side-polished spiral structure. The POF is wound around a plastic rod with the same pitch and polished into a series of separated side-polished areas to form the sensor probe. Afterwards, the polished surfaces are coated with a gold layer to construct the SPR sensor. The proposed sensor can provide multi-point liquid-level measurement besides RI sensing. The influences of structural parameters such as the bending radius, polishing depth, and pitch on the sensing performance are experimentally studied. The experimental results indicate that the RI could be determined by employing the SPR wavelength shift, and the RI sensitivity of 1862 nm/RIU within the 1.34–1.40 range is obtained. Moreover, the SPR peak’s depth variation can be utilized to monitor the liquid level, and the sensor can provide adjustable resolution and a measurement range for liquid level sensing. With its simple fabrication, low cost, and flexible sensing ability, this sensor probe is suitable for the usage in biochemical applications.
To further improve sensor sensitivity, a strain and temperature sensor based on the harmonic Vernier effect with cascaded Sagnac interferometers (SIs) is proposed. Through a combination of simulation and experimentation, it is shown that the basic Vernier effect can be realized when the lengths of the polarization-maintaining fiber (PMF) in two SIs are slightly different. Furthermore, the first-order harmonic Vernier effect can be achieved when the lengths of two PMFs are approximately integer multiples. This sensor, leveraging the harmonic Vernier effect, demonstrates higher sensitivity. Compared to a single SI, the strain sensitivity based on the basic Vernier effect is improved to 61.93 pm/με with a magnification factor of 7.6, and the temperature sensitivity is improved to 14.29 nm/°C with a magnification factor of 9.4. For the first-order harmonic Vernier effect, the strain sensitivity increases to 146.35 pm/με with a magnification factor of 18, and the temperature sensitivity increases to 24.92 nm/°C with a magnification factor of 16.5. Additionally, the sensor based on the harmonic Vernier effect exhibits good stability in strain and temperature measurement. Unlike the basic Vernier effect, the harmonic Vernier effect does not require strict control of the reference and sensing interferometer lengths, further increasing sensitivity. Due to its simple structure and low cost, the proposed sensor shows significant potential for applications in high-precision measurement engineering and medical treatment.
Polarization cameras including 4-directional micro-polarizer array sensors are a very novel technology that have shown potential for fast and in-situ polarimetric measurement, which results in very appealing in applications, such as biomedical, astronomy, remote sensing, or industry. However, the use of these cameras leads to overdetermined measurement that needs a calibration method according to the particular design and measurement scheme. We presented the required considerations by successfully use the eigenvalue calibration method, which was implemented in the Mueller polarimeters based on polarimetric cameras, where the number of analyzed polarization states was n≥8. We also studied the optimal set of calibration samples to achieve a more robust calibration. The proposed combination of calibration samples was independent of the dimensions and condition of the instrument matrices and can be extended to other variants of the eigenvalue calibration method. The calibration method and implementation of the polarimeter were validated through experimental measurements of the Mueller matrices of rotating polarizers and quarter-wave plates.
Magnetic field measurement sensing techniques have a wide range of applications in scientific research and industrial production. The whispering gallery mode (WGM) resonators, known for their ultra-high-quality factor (Q), offer exceptional resolution for high-precision magnetic field sensing. However, since most resonator materials are inherently insensitive to magnetic fields, they need to be combined with magnetically sensitive materials to form complex sensing structures. This paper proposed an ultrasimple structure that directly utilized an yttrium iron garnet (YIG) resonator as the magnetic field sensing unit. Based on the magnetostrictive effect, the YIG resonator was stretched in the parallel magnetic field direction and contracted in the vertical direction. High sensitivity magnetic field measurement was achieved by detecting the resonance frequency drift caused by resonator deformation. The experimental results showed that the direct current (DC) magnetic field had sensitivity of 14.81 MHz/mT in the range of 2 mT-7 mT, and the peak alternating current (AC) magnetic field sensitivity was 8.6 nT/Hz1/2 at 774 kHz, with the depth of the concavity of 23.4 dB in the scaling factor direction curve. The sensing device offers the advantages of an ultrasimple structure and high sensitivity, making it highly promising for a wide range of applications.
A sensor based on an infrared dual-band polarization-insensitive metamaterial absorber is proposed, which consists of a square ring layer at the top, a silicon dielectric layer at the bottom, and a metal layer at the bottom. By using the finite element method (FEM), for the transverse electricity (TE) and transverse magnetic (TM) mode incidence, the absorption rates of the resonant point at 4.75 µm are 0.950 and 0.943, and the absorption rates at 7.85 µm can reach 0.997 and 0.998, respectively. Because of the symmetry of the structure, the absorber is not sensitive to polarization when it is vertically incident and can still maintain good absorption performance in a wide range of incidence angles. For commonly used aqueous solutions (sodium chloride, glucose, sucrose, etc.), the refractive index of the aqueous solution is in the range of 1.33 to 1.48 and the sensing test is performed. For the TE mode, the sensing sensitivity is about 2 283.05 nm/RIU through linear fitting, and the quality factor Q is 108.38. For the TM mode, the sensing sensitivity is about 2 371.43 nm/RIU through linear fitting, and the quality factor Q is 84.50, which has better sensing characteristics. The absorber sensor designed in this paper achieves high sensitivity in the infrared, has a high Q value, is easy to manufacture, and plays a huge advantage in the field of high-sensitivity detection.