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Incoherent Gain-Assisted Ring Enhanced Gas Absorption Spectroscopy
摘要： A novel incoherent gain-assisted ring enhanced spectroscopy technique is presented overcoming the need for precise optical alignment and high reflectivity dielectric mirrors. A gain medium pumped below the lasing threshold is used to improve the ring finesse and, thus, the interaction length. Two configurations are considered and compared. The first configuration is dual coupler ring with the source outside the ring and the gain medium inside the ring, while the second configuration is single coupler resonator with the gain medium acting as the source. The configurations are studied analytically and experimentally for different system parameters. The experimental results are obtained for a coupling ratio of 90/10. The broadband source is the amplified spontaneous emission of a semiconductor optical amplifier (SOA), while another SOA is used as the gain medium. Acetylene (C2H2) gas absorption is measured around 1540 nm wavelength. The output spectrum of the ring is measured using a 70 pm resolution. The interaction length is found to be enhanced by a factor of 9.35 and 44 in case of the dual coupler and single coupler resonator, respectively, compared to the direct absorption of the gas cell.
关键词： Gas spectroscopy,effective length enhancement,fiber sensors,finesse enhancement,incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS),active fiber cavities
更新于2025-09-23 15:23:52
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Advanced methods for the optical quality assurance of silicon sensors
摘要： We describe a setup for optical quality assurance of silicon microstrip sensors. Pattern recognition algorithms were developed to analyze microscopic scans of the sensors for defects. It is shown that the software has a recognition and classification rate of >90% for defects like scratches, shorts, broken metal lines etc. We have demonstrated that advanced image processing based on neural network techniques is able to further improve the recognition and defect classification rate.
关键词： video microscope,silicon sensors,neural networks,optical quality assurance
更新于2025-09-23 15:23:52
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Metal ion induced single-crystal-to-single-crystal transformation and luminescent sensing properties of resorcin arene-based metal-organic frameworks
摘要： In this work, two new resorcin[4]arene-based metal-organic frameworks (MOFs), namely, [(CH3)2NH2][Zn3(HL)(L)(DMF)(H2O)2]·2H2O (1-Zn) and [(CH3)2NH2]2[Cd3(L)2(H2O)4]·2DMF·2H2O (2-Cd), have been synthesized under solvothermal conditions (H4L represents the resorcin[4]arene-based ligand). 1-Zn exhibits a layer structure, while 2-Cd shows a 3D motif. Remarkably, by immersing 1-Zn in an aqueous solution of Cu2+ ions, a new Cu(II)-MOF [Cu2(H2L)2(H2O)2]·3.5H2O (1-Cu) was achieved via a metal ion induced single-crystal-to-single-crystal (SCSC) transformation manner, involving generation of new metal-O bond and change of metal ion coordination geometry. Moreover, luminescent detection properties for Fe3+ ions and Cr2O7 2- ions were also investigated with 1-Zn and 2-Cd as luminescent sensors.
关键词： Resorcin[4]arene,Metal-exchanged phrase transformation,Metal-organic framework,Luminescent sensors
更新于2025-09-23 15:23:52
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Combination of Pd loading and electron beam irradiation for superior hydrogen sensing of electrospun ZnO nanofibers
摘要： We evaluated the hydrogen gas-sensing characteristics of Pd-loaded (0.1, 0.3, 0.6, and 1 wt%) ZnO nano?bers prepared by a facile electrospinning technique and the e?ect of di?erent electron beam (e-beam) doses (50, 100, and 150 kGy) on sensing performance. The sensor loaded with 0.6 wt% Pd had the highest response to hydrogen among the Pd-loaded sensors. The sensor irradiated with 150 kGy had the high response (Ra/Rg) of 74.7–100 ppb of H2 at 350 °C. Metallization e?ects in ZnO, the formation of structural defects due to e-beam irradiation, the catalytic activity of Pd, and the presence of ZnO–Pd heterojunctions were the main factors yielding high sensitivity towards H2. The strategy of combining e-beam irradiation and Pd loading to enhance H2 sensing can be applied to realize reliable gas sensors and the widespread use of hydrogen as a green energy alternative to fossil fuels.
关键词： H2,Electron beam irradiation,Gas sensors,ZnO nano?bers,Pd nanoparticles
更新于2025-09-23 15:23:52
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Understanding the Sensing Mechanism of Rh2O3 loaded In2O3
摘要： The effect of Rh loading on CO sensing was studied for the case of In2O3. This was done by performing measurements with sensors based on loaded and unloaded materials that were performed at an operation temperature of 300 °C in the presence of low background oxygen concentration according to an experimental procedure that was demonstrated to help clarify the reception/transduction functions of loaded Semiconducting Metal Oxides (SMOX). The experimental investigation methods were DC resistance and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that in the case of Rh2O3 loaded In2O3 the reaction primary takes place on the Rh2O3 cluster and the electrical properties of the In2O3 are controlled by the pinning of the SMOX Fermi-level to the one of the Rh2O3 cluster.
关键词： SMOX,surface chemistry,gas sensors,operando,Rh2O3 loading,DRIFTS,In2O3
更新于2025-09-23 15:23:52
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Novel interfacial bulk heterojunction technique for enhanced response in ZnO nanogenerator
摘要： In this paper, a direct sustainable approach for the development of n-ZnO:p-CuO heterojunction (ZCH) through a simple grinding is reported to be an effective technique to enhance the piezoelectric performance of ZCH/PDMS nanocomposite-based nanogenerator (ZP-PNG). We have first optimized the best concentration for ZnO/PDMS nanocomposite for the realization of the piezoelectric nanogenerator. Later, with the same configuration, we implemented a novel, simple, facile, frugal and inexpensive technique to fabricate ZCH. The heterojunction results in the improved charge transfer characteristics, low capacitance and charge nullification contributing to the enhanced piezoelectric output. This reflects in the improvement of the peak to peak piezoelectric potential of the device from 2.7 V to 9V. The instantaneous max power density was found to be 0.2 mW/m2.The device can work as a force sensor with improved sensitivity of 1.7 V/N compared to 1.05 V/N of the intrinsic device. The device being systematically studied for load matching, and capacitor charging to demonstrate the practicability of the device. Furthermore, we tested our device to harness the biomechanical energy from day to day life activities. Finally, the device was used to fabricate sustainable piezoelectric based smart urinal (PSU) systems for low-income group countries.
关键词： composite,heterojunction,sustainable smart sensors,piezoelectric,ZnO
更新于2025-09-23 15:23:52
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Sheath-Core Fiber Strain Sensors Driven by In-Situ Crack and Elastic Effects in Graphite Nanoplate Composites
摘要： The flexible and stretchable electronics, e.g., graphite nanoplatelets (GNPs) based nanocomposite devices, have attracted great interest due to their potential application in healthcare, robotics, and mechatronics technology. However, the deficient sensors with manipulation of low sensitivity, sluggish responsivity, sophisticated fabrication process and poor repeatability notoriously limit their industrial applications. To enhance the spontaneous sensitivity, flexibility and wearability in GNPs based strain sensors, in this report, the synergistic crack and elastic effects engineering is employed and in turn significantly enhances the sensitivity with the gauge factor of 20 at the strain of 30% and the stability in our developed sheath-core fiber (SCF) strain sensors. Upon reliable devices integration, it is demonstrated that the developed SCF strain sensor could detect the movement of human joint effectively with generating a resistance change rate ΔR/R0 up to 600%. Furthermore, a controlling devices system based on SCF strain sensor has been manufactured in circuit level to realize the real-time control of a robot hand, such as copying gestures and playing piano.
关键词： Graphite nanoplatelets (GNPs),Robotic mechatronics,Sheath–core structure,Strain sensors,Crack and elastic effects
更新于2025-09-23 15:23:52
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Interfacial adhesion between embedded fibre optic sensors and epoxy matrix in composites
摘要： Fibre optic (FO) sensors are becoming increasingly popular for different applications in structural monitoring. Among their excellent properties, a strong interest for this type of sensors are represented by the possibility of embedding FOs inside composite components. In this case, one of the factors that significantly influence the efficiency of the whole Structural Health Monitoring (SHM) system is the interfacial adhesion between FO sensors and the host material. The main objective of this work is to investigate the interfacial adhesion between embedded fibre optic sensors and epoxy matrix to find the best type of optical fibre to be used in epoxy matrices to produce smart composites. Four types of optical fibres with different diameters and coatings (i.e. polyimide, polyacrylate and ormoceramic) were used. Pull-out tests were carried out and different methods were used to obtain the composite/optical fibre interfacial properties. Finally, an optical microscopy and Scanning Electron Microscopy (SEM) analysis were performed to characterize the fibre/matrix interfaces. It was found that the optical fibre that presented the highest energy required for interface rupture and, consequently, less invasiveness to the host material was the ormoceramic fibre with the smallest diameter.
关键词： Structural health monitoring,Pull-out test,interfacial adhesion,fibre optics sensors
更新于2025-09-23 15:23:52
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Exceptional Points of Degeneracy Induced by Linear Time-Periodic Variation
摘要： We present a general theory of exceptional points of degeneracy (EPD) in periodically time-variant systems. We show that even a single resonator with a time-periodic component is able to develop EPDs, contrary to parity-time- (PT) symmetric systems that require two coupled resonators. An EPD is a special point in a system parameter space at which two or more eigenmodes coalesce in both their eigenvalues and eigenvectors into a single degenerate eigenmode. We demonstrate the conditions for EPDs to exist when they are directly induced by time-periodic variation of a system without loss and gain elements. We also show that a single resonator system with zero time-average loss-gain exhibits EPDs with purely real resonance frequencies, yet the resonator energy grows algebraically in time since energy is injected into the system from the time-variation mechanism. Although the introduced concept and formalism are general for any time-periodic system, here, we focus on the occurrence of EPDs in a single LC resonator with time-periodic modulation. These findings have significant importance in various electromagnetic and photonic systems and pave the way for many applications, such as sensors, amplifiers, and modulators. We show a potential application of this time-varying EPD as a highly sensitive sensor.
关键词： exceptional points of degeneracy,time-periodic systems,sensors,modulators,LC resonator,amplifiers
更新于2025-09-23 15:23:52
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Microwave Photonic Signal Processing and Sensing Based on Optical Filtering
摘要： Microwave photonics, based on optical filtering techniques, are attractive for wideband signal processing and high-performance sensing applications, since it brings significant benefits to the fields by overcoming inherent limitations in electronic approaches and by providing immunity to electromagnetic interference. Recent developments in optical filtering based microwave photonics techniques are presented in this paper. We present single sideband modulation schemes to eliminate dispersion induced power fading in microwave optical links and to provide high-resolution spectral characterization functions, single passband microwave photonic filters to address the challenges of eliminating the spectral periodicity in microwave photonic signal processors, and review the approaches for high-performance sensing through implementing microwave photonics filters or optoelectronic oscillators to enhance measurement resolution.
关键词： Microwave photonics,photonic filtering,photonic signal processing,single sideband modulation,single passband microwave photonic filter,optical sensors
更新于2025-09-23 15:23:52