Highly sensitive digital optical sensor with large measurement range based on the dual-microring resonator with waveguide-coupled feedback

We propose a novel high-performance digital optical sensor based on the Mach-Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback. The simulation results show that the sensitivity of the sensor can be orders of magnitude higher than that of aconventional sensor, and high quality factor is not critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.

Optical sensors based on the NiPc-CoPc composite films deposited by drop casting and under the action of centrifugal force

In this study, solution processed composite films of nickel phthalocyanine（NiPc） and cobalt phthalocyanine（CoPc）are deposited by drop casting and under centrifugal force. The films are deposited on surface-type inter-digitated silver electrodes on ceramic alumina substrates. The effects of illumination on the impedance and capacitance of the NiPc–CoPc composite samples are investigated. The samples deposited under centrifugal force show better conductivity than the samples deposited by drop casting technique. In terms of impedance and capacitance sensitivities the samples fabricated under centrifugal force are more sensitive than the drop casting samples. The values of impedance sensitivity（Sz）are equal to（-1.83） MΩ·cm^2/mW and（-5.365） MΩ·cm^2/mW for the samples fabricated using drop casting and under centrifugal force, respectively. Similarly, the values of capacitance sensitivity（Sc） are equal to 0.083 pF·cm^2/mW and 0.185 pF·cm～2/mW for the samples fabricated by drop casting and under centrifugal force. The films deposited using the different procedures could potentially be viable for different operational modes（i.e., conductive or capacitive） of the optical sensors. Both experimental and simulated results are discussed.

Design of fan beam optical sensor and its application in mass flow rate measurement of pneumatically conveyed solids

The fan-beam optical sensor is made up of many semiconductor lasers and detectors fixed around the wall alternately at a cross section of pneumatically conveying pipe. When the sensor works, a scanning light source emits a 50° lamellar fan-beam through the gas-solid two phase flow, and the projection data resulting extinction effect of solid particles are detected at the same time. With the projection data, the flow rate mass can be calculated, and then the flow image can be reconstructed. In this paper, the design of the sensor including spatial arrangement of the structural parts, basic principle and measurement sensitivity distribution are introduced. The mathematical measurement model of solid mass flow rate is presented together with the testing results.

Optical sensor for BTEX detection:Integrating machine learning for enhanced sensing

Optical sensors provide a fast and real-time approach to detect benzene,toluene,ethylbenzene,and xylenes(BTEX)in environmental monitoring and industrial safety.However,detecting the concentration of a particular gas in a mixture can be challenging.Here,we develop a machine-learning model that can precisely measure BTEX concentrations simultaneously based on an absorption spectroscopy gas sensing system.The convolutional neural network(CNN)is utilized to identify the absorbance spectra for each volatile,along with their concentrations in a mixture.A synthetic data set is generated using a series of physics-based simulations to create the predictive model.The data set consists of the overall absorbance of numerous random BTEX mixtures over time,based on various percentages of the permissible exposure limit(PEL).It is worth noting that benzene has a negligible absorbance(very low PEL,1–5 ppm)compared to other volatile gases,which makes it difficult to detect.To address this challenge,we introduce a 3-stage solution to accurately discriminate between all BTEX species,regardless of their concentration levels.As a result,the R-squared above 0.99 for toluene,ethylbenzene,and oxylene,and the R-squared above 0.96 for benzene,is achieved,indicating the model's capability to predict BTEX concentrations.

Liquid Crystal Based Label-Free Optical Sensors forBiochemical Application

Biochemical sensors have important applications in biology,chemistry,and medicine.Nevertheless,many biochemical sensors are hampered by intricate techniques,cumbersome procedures,and the need for labeling.In the past two decades,it has been discovered that liquid crystals can be used to achieve the optical amplification of biological interactions.By modifying recognition molecules,a variety of label-free biochemical sensors can be created.Consequently,biochemical sensors based on the amplification of liquid crystals have become one of the most promising sensors.This paper describes in detail the optical sensing principle of liquid crystals,sensing devices,and optical detection technologies.Meanwhile,the latest research findings are elucidated.Finally,the challenges and future research directions are discussed.

Functional Optical Fiber Sensors Detecting Imperceptible Physical/Chemical Changes for Smart Batteries

The battery technology progress has been a contradictory process in which performance improvement and hidden risks coexist.Now the battery is still a“black box”,thus requiring a deep understanding of its internal state.The battery should“sense its internal physical/chemical conditions”,which puts strict requirements on embedded sensing parts.This paper summarizes the application of advanced optical fiber sensors in lithium-ion batteries and energy storage technologies that may be mass deployed,focuses on the insights of advanced optical fiber sensors into the processes of one-dimensional nano-micro-level battery material structural phase transition,electrolyte degradation,electrode-electrolyte interface dynamics to three-dimensional macro-safety evolution.The paper contributes to understanding how to use optical fiber sensors to achieve“real”and“embedded”monitoring.Through the inherent advantages of the advanced optical fiber sensor,it helps clarify the battery internal state and reaction mechanism,aiding in the establishment of more detailed models.These advancements can promote the development of smart batteries,with significant importance lying in essentially promoting the improvement of system consistency.Furthermore,with the help of smart batteries in the future,the importance of consistency can be weakened or even eliminated.The application of advanced optical fiber sensors helps comprehensively improve the battery quality,reliability,and life.

Quantitative Identification of Delamination Damage in Composite Structure Based on Distributed Optical Fiber Sensors and Model Updating

Delamination is a prevalent type of damage in composite laminate structures.Its accumulation degrades structural performance and threatens the safety and integrity of aircraft.This study presents a method for the quantitative identification of delamination identification in composite materials,leveraging distributed optical fiber sensors and a model updating approach.Initially,a numerical analysis is performed to establish a parameterized finite element model of the composite plate.Then,this model subsequently generates a database of strain responses corresponding to damage of varying sizes and locations.The radial basis function neural network surrogate model is then constructed based on the numerical simulation results and strain responses captured from the distributed fiber optic sensors.Finally,a multi-island genetic algorithm is employed for global optimization to identify the size and location of the damage.The efficacy of the proposed method is validated through numerical examples and experiment studies,examining the correlations between damage location,damage size,and strain responses.The findings confirm that the model updating technique,in conjunction with distributed fiber optic sensors,can precisely identify delamination in composite structures.

A novel orientation measurement using optical sensor for spherical motor

The measurement of spherical rotor orientation is crucial to the close-loop control of spherical motors. This paper presents a novel method for the measuring of three-degree-of-freedom (DOF) rotor orientation of spherical motors using optical sensors. The spatial orientation of spherical rotor is output in the form of ZXZ Euler angles. Firstly, the structure of the measuring system composed of optical sensors and the patterns on the rotor surface are presented, and the operational principle of recognizing intersection points between the optical ring detectors and the latitude/longitude on the rotor surface is illustrated. The analytical model of input-output characteristic is established for the measuring system of three-DOF rotor orientation. Afterwards, the effect of parameters of the optical ring detectors on the linearity, sensitivity, resolving power and measuring range of the measuring system is analyzed using the analytical model. Finally, the feasibility of the measurement is validated through experiments of prototype measuring system. The analysis is expected to be a basis for the design parameter optimization of the orientation measuring system of a PM spherical motor.

Visualized optical sensors based on two/three-dimensional photonic crystals for biochemicals

Responsive photonic crystals(RPCs) constructed by periodic two/three-dimensional(2D/3D) photonic crystals(PCs) and responsive-material hosts,are important visualized optical sensors.Their optical diffraction color can be tuned reversibly by external stimuli,such as pH,metal ions,biomolecules,vapors and solvents,hence leading to wide applications as visualized sensors.This review introduces the recent progress of RPCs based on 2D/3D PCs for visual detection of chemical and biological analytes,including the preparation of 2D PCs,3D PCs films,3D PCs microbeads and their applications as visualized sensors.The different cases of detecting various chemical and biological analytes by naked eyes are presented.Emphasis is given to the description of their respective sensing mechanisms with the different systems for chemical and biological analytes.Compared with 3D RPCs sensors,2D RPCs sensors have shorter response time,better stabilization and higher production efficiency,however,the diffraction intensity of 2D RPCs based on monolayered 2D polystyrene(PS) microsphere array are weak.2D RPCs sensors based on 2D Au nanosphere can significantly improve the diffraction intensity compared with traditional 2D RPCs sensors based on monolayered PS microsphere array.The much higher scattering cross section of Au nanosphere leads to 2D Au nanosphere array with ultrahigh optical diffraction intensity,which are highly helpful for their practical application as visual sensors and further quantitative detection by monitoring the diffraction peak position and intensity.

Multifunctional flexible optical waveguide sensor: on the bioinspiration for ultrasensitive sensors development

This paper presents the development of a bioinspired multifunctional flexible optical sensor(BioMFOS)as an ultrasensitive tool for force(intensity and location)and orientation sensing.The sensor structure is bioinspired in orb webs,which are multifunctional devices for prey capturing and vibration transmission.The multifunctional feature of the structure is achieved by using transparent resins that present both mechanical and optical properties for structural integrity and strain/deflection transmission as well as the optical signal transmission properties with core/cladding configuration of a waveguide.In this case,photocurable and polydimethylsiloxane(PDMS)resins are used for the core and cladding,respectively.The optical transmission,tensile tests,and dynamic mechanical analysis are performed in the resins and show the possibility of light transmission at the visible wavelength range in conjunction with high flexibility and a dynamic range up to 150 Hz,suitable for wearable applications.The BioMFOS has small dimensions(around 2 cm)and lightweight(0.8 g),making it suitable for wearable application and clothing integration.Characterization tests are performed in the structure by means of applying forces at different locations of the structure.The results show an ultra-high sensitivity and resolution,where forces in theμN range can be detected and the location of the applied force can also be detected with a sub-millimeter spatial resolution.Then,the BioMFOS is tested on the orientation detection in 3D plane,where a correlation coefficient higher than 0.9 is obtained when compared with a gold-standard inertial measurement unit(IMU).Furthermore,the device also shows its capabilities on the movement analysis and classification in two protocols:finger position detection(with the BioMFOS positioned on the top of the hand)and trunk orientation assessment(with the sensor integrated on the clothing).In both cases,the sensor is able of classifying the movement,especially when analyzed in conjunction with preprocessing and clustering techniques.As another wearable application,the respiratory rate is successfully estimated with the BioMFOS integrated into the clothing.Thus,the proposed multifunctional device opens new avenues for novel bioinspired photonic devices and can be used in many applications of biomedical,biomechanics,and micro/nanotechnology.

Design of a Porous Cored Hexagonal Photonic Crystal Fiber Based Optical Sensor With High Relative Sensitivity for Lower Operating Wavelength

In this article, highly sensitive and low confinement loss enriching micro structured photonic crystal fiber （PCF） has been suggested as an optical sensor. The proposed PCF is porous cored hexagonal （P-HPCF） where cladding contains five layers with circular air holes and core vicinity is formed by two layered elliptical air holes. Two fundamental propagation characteristics such as the relative sensitivity and confinement loss of the proposed P-HPCF have been numerically scrutinized by the full vectorial finite element method （FEM） simulation procedure. The optimized values are modified with different geometrical parameters like diameters of circular or elliptical air holes, pitches of the core, and cladding region over a spacious assortment of wavelength from 0.8 ktm to 1.8 -m. All pretending results exhibit that the relative sensitivity is enlarged according to decrement of wavelength of the transmission band （O＋E＋S＋C＋L＋U）. In addition, all useable liquids reveal the maximum sensitivity of 57.00%, 57.18%, and 57.27% for n=1.33, 1.354, and 1.366 respectively by lower band. Moreover, effective area, nonlinear coefficient, frequency, propagation constant, total electric energy, total magnetic energy, and wave number in free space of the proposed P-HPCF have been reported recently.

Laboratory evaluation of the GreenSeeker^(TM) handheld optical sensor to variations in orientation and height above canopy

Handheld optical sensors recently have been introduced to the agricultural market.These handheld sensors are able to provide operators with Normalized Difference Vegetative Index(NDVI)data when cloud cover prevents acquisition of satellite or aerial images.This research addressed the sensitivity of the GreenSeeker handheld optical sensor to changes in orientation and height above a ryegrass canopy.Planter boxes were oriented both parallel and perpendicular to the light beam from the sensor head and heights of 30.5 cm(12”),61.0 cm(24”),91.5 cm(36”),122 cm(48”)and 152 cm(60”)were tested.Results indicated that the sensor was highly sensitive(P<0.0001)to both height above canopy and orientation of the sensor relative to the target.Operators should follow manufacturer’s recommendations on operating height range of 81-122 cm and orient the sensor head in-line with the target to obtain maximum signal response.

A novel Cu(I) complex based organic ultraviolet optical sensor

A novel Cu(I) complex with the formula of [Cu(DPEphos)(Dicnq)]BF4(CuDD) was synthesized and characterized by X-ray single crystal diffraction method,in which DPEphos and Dicnq denote bis[2-(diphenylphosphino)phenyl]ether and 6,7-Dicyanodipyrido[2,2-d:2 ,3 -f] quinoxaline,respectively.Organic ultraviolet optical sensor based on photovoltaic diode is fabricated by using CuDD as an electron acceptor and 4,4′,4″-tris-(2-methylphenyl phenylamino) triphenylamine(m-MTDATA) as an electron donor.The sensor is sensit...

Surface plasmon excitation in semitransparent inverted polymer photovoltaic devices and their applications as label-free optical sensors

Herein,we report on surface plasmon(SP)-sensitive semitransparent inverted polymer photovoltaic(PV)devices that are based on multilayered material systems consisting of poly(3-hexylthiophene):fullerene-derivative bulk-heterojunction PV layers and thin gold or silver anodes.We demonstrate that these PV devices allow the simultaneous generation of both electrical power and SPs on their anodes for photoexcitation just above the optical absorption edge of the PV layers,resulting not only in attenuated total reflection,but also in attenuated photocurrent generation(APG)under the SP resonance(SPR)condition.Moreover,we also confirm that the biomolecular interaction of biotin–streptavidin on the PV devices can be precisely detected via apparent SPR angle shifts in the APG spectra,even without the need for complex attenuated total reflection configurations.We highlight our view that APG measurements made using these PV devices show great potential for the development of future generations of compact and highly sensitive SPR-based optical sensors.

Asymmetric Fabry-Pérot interferometric cavity for fiber optical sensors

Good linearity and wide dynamic range are the advantages of asymmetric Fabry-Pérot （F-P） interferometric cavity, whose realization has been long for. Based on optical thin film characteristic matrix theory, an asymmetric F-P interferometric cavity with good linearity and wide dynamic range is designed. And by choosing the material of two different thin metallic layers, the asymmetric F-P interferometric cavity is successfully fabricated. The design theory and method of this asymmetric F-P interferometric cavity have been described in detailed. In this paper an asymmetric F-P interferometric cavity used in fiber optical sensor is reported.

AN OPTICAL FIBER SENSOR TECHNIQUE BASED ON SLIGHT DISTURBANCE RADIATION LOSS OF STOCHASTIC WALL

This paper presents an optical sensor technique used in the damage evaluation which is formed by structurally integrated fiber optic reticulate sensors embedded in the composite materials. The fibers are processed by chemical method and their outsides are peeled to form particles of irregular distribution and they differ in size, so the slight disturbance range of stochastic wall are formed in fibers. According to the characteristics of power loss of waveguide mode caused by slight disturbance of stochastic wall and radiative mode transmission, the range of slight disturbance of stochastic wall may be served as the sensitive range of the sensor. On the basis of theory of slight disturbance of stochastic wall of planar optical waveguide, the relation between the corrosion time and the opposite power loss by experiments is investigated. In this paper, the measurement results of object of SIFORS are also presented. The results show that the optical sensor technique may be used in the damage evaluation of an aircraft.

Reflex optical sensor based on dual metal gratings with high angular sensitivity

An interesting reflection phenomenon in a dual metal grating （DMG） structure is studied, which is related to the competition between Fabry-Prot （F-P） resonance effect and evanescent-field coupling effect inside the gap between the two composing single metal gratings. This competition leads to high angular sensitivity in response to the refractive index variation of the sample solution in the gap. A reflex optical sensor with high sensitivity based on DMG for detecting the change in refractive index is proposed and its performance theoretically is discussed.

Air-blast anti-fouling cleaning for aquatic optical sensors

In order to solve the problem of fouling of submerged optical instruments,an air-blast cleaning mechanism was integrated into an optical sensor used for measuring suspended sediment concentration(SSC)in natural waters.Laboratory experiments in a manually created fouling environment were conducted to observe the fouling process on sensor cases made of different materials,and to verify the effectiveness of air-blast cleaning in reducing fouling.Results indicated that sensors with an aluminum case experienced more serious bio-fouling than that with polyethylene case,and the air-blast cleaning mechanism was capable of reducing fouling effect on sensor signals.So the submerged optical instruments should avoid using metal materials.The duration and frequency of air-blast cleaning can be determined and adjusted depending on actual field conditions.

A New Highly Sensitive Optical Sensor Based on Congo-Red for the Determination of Thorium(Ⅳ) in Aqueous Solution

This essay explores the use of the sol-gel method based on the Congo-red reagent as an effective approach to create an optical sensor for the detection and tracking of Thorium(Ⅳ)(Th^(4+)).Upon exposure to a Th^(4+)-containing solution,the sensor exhibits significant absorption signal change that linearly correlates with Th^(4+)ion concentration across a wide range.It is capable of detecting Th^(4+)ion in the linear dynamic range of 1.7×10^(-8)to 1.1×10^(-3)mol/L,with a detection limit of 5.3×10^(-9)mol/L.This optode’s exceptional porous network,created through the sol-gel technique,contributes to its commendable performance,reliable repeatability,improved sensitivity,swift response time,and discerning selectivity.

Sensors for control of water transparency in optical and microwave ranges

In the face of deteriorating environmental conditions in the world,water quality control is an urgent task.It can be solved by creating sensors with high accuracy and low cost,which requires the development of fundamentally new radiophysical methods that take advantage of the optical,microwave and millimeter wavelengths that have a significantly greater sensitivity to low concentrations of pollutants and a lower inertia.The article presents prototypes of measuring cells of the microwave and optical ranges as well as the results of an experimental study of water of various degrees of pollution with their help.The results show that the use of the highly sensitive method of capillary-waveguide resonance makes it possible to detect the presence of micro impurities in water with concentrations up to0.1%and to identify water even from sources of various natural origins.In addition,the use of measurements at several frequencies in the optical range will make it possible to solve the problem of creating water control sensors with high sensitivity to pollution and low cost.It can be concluded that the possibility of complex use of multiwave sensors(optical,infrared and microwave ranges)allows to increase the sensitivity and reliability of water quality assessment.