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Stable injection locking with slotted Fabry–Perot lasers at 2 <i>μ</i> m
摘要： Injection locking has many applications in telecommunications systems, such as narrowing linewidths, increasing bandwidth and improving filtering. Beyond telecommunications, injection locking is widely used in remote sensing. This is of particular interest for applications in the 2 μm region, where gases such as carbon dioxide, water vapour and methane have identifiable absorption features. In this paper, we demonstrate stable injection locking with slotted Fabry–Perot lasers in the 2 μm wavelength region. Injection locking was observed in both the optical domain and power spectrum; with key features recorded such as injection ‘pulling’, side-mode suppression and the characteristic quiet region in the electrical domain denoting single-frequency emission and stable locking. The effect of varying the injection ratio was investigated, with a decreased injection ratio corresponding to a reduction in the locking bandwidth. Finally, the lasers were shown to remain injection locked, with no thermal drift, for over 24 h, indicating their suitability for implementation in a real-world telecommunications system.
关键词： injection-locked lasers,semiconductor lasers,optical communications,optical sensing and sensors
更新于2025-11-28 14:23:57
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Encyclopedia of Robotics || Vision for the Marine Environment
摘要： Vision for the Marine Environment refers to underwater imaging hardware and algorithms that enable the perception of the subsea environment for marine science applications, inspection and intervention. For a long time, optical cameras have been used in ROVs to provide the user with visual feedback of the operational scene. Conversely, AUVs have been traditionally equipped with sonar imaging systems, for two main reasons. First, the range of acoustic imaging is significantly higher, and second, as a consequence, they can work at a safer altitude, while the AUV follows the bottom profile. Nevertheless, during the last decades, vision systems have become smaller and more power-efficient, and the robot hardware has become more powerful and capable of storing the images onboard. Nowadays, commercial AUVs may be equipped with vision systems able to provide high-resolution seafloor imagery in clear waters. A single AUV survey may provide many thousands of images making it tedious to analyze the results. Image processing techniques may significantly improve the quality of the images and combine them into maps enabling faster interpretation. While the role of vision in commercial off-the-shelf robots is mostly passive (they gather data that is later processed after the mission), there have been research contributions aimed at incorporating computer vision algorithms to make the robot more autonomous, adapting its behavior online depending on the sensed situation. Algorithms for pipe/cable tracking, visual odometry, station-keeping, or target-tracking among others are paving the way toward an enhanced breed of autonomous robot, exploiting vision as a primary sensor modality.
关键词： Underwater computer vision,Underwater optical sensing and processing
更新于2025-09-23 15:22:29
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Optimising porous silicon Bragg reflectors for narrow spectral resonances
摘要： Achieving sharp spectral resonances in porous silicon based photonic structures is of significant practical importance for improving the accuracy of refractive index-based sensing in chemical and biochemical applications. Here, we show that by compensating for depth related heterogeneities in the etching conditions, we are able to reduce the porosity modulation in Bragg reflectors to below 1% and achieve absorption limited spectral widths of 7 nm in the visible part of the spectrum. Such narrowband Bragg reflectors provide markedly improved sensing capability for real-time monitoring of refractive index changes compared with reflectors with broader spectral features.
关键词： optical sensing,porous silicon,Bragg reflectors,narrow spectral resonances,refractive index-based sensing
更新于2025-09-23 15:21:21
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Photonic integrated multiwavelength laser arrays: Recent progress and perspectives
摘要： With the significant technology advancement in photonic integration and the demands of compact light sources of multiple wavelengths, multiwavelength laser arrays (MWLAs) can play important roles in high-capacity optical signal transmission, photonic switching, and optical sensing. Manufacturing with semiconductor foundries and the integration with electronic integrated circuits bring not only advanced technologies but also new concepts for realizing MWLAs. This paper will first overview the existing technology development and then discuss the challenges and possible solutions for enabling photonic-integrated MWLAs. The overview will cover monolithically and hybrid-integrated MWLAs. The wavelength registration for both in-plane and vertical-cavity MWLAs will be discussed and compared.
关键词： photonic switching,optical signal transmission,optical sensing,multiwavelength laser arrays,photonic integration
更新于2025-09-23 15:21:01
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Vapor Sensing with Polymer Coated Straight Optical Fiber Microtapers Based on Index Sensitive Interference Spectroscopy of Surface Stress Birefringence
摘要： Optical micro?ber tapers provide an advantageous platform for sensing in aqueous and gas environments. We study experimentally the photonic transmission in optical ?ber tapers coated with polymethyl methacrylate (PMMA), a polymeric material widely used in optical applications. We demonstrate a durable and simple humidity sensing approach incorporating tapered micro?bers attached to silicon (Si) substrate coated with active polymer layer. A model is described for the load stress effect on the birefringence giving rise to interferences in the transmission spectra, strongly dependent on the coating layer thickness, and disappearing following its slow uniform removal. The sensing approach is based on characterization of the interference patterns observed in the transmission spectra of the taper in the NIR range. The device demonstrated persistent detection capability in humid environment and a linear response followed by saturation to calibration analytes. In each analyte of interest, we de?ne principal components and observe unique calibration plot regimes in the principal component space, demonstrating vapor sensing using polymer coated microtapers.
关键词： microstructured ?bers,optical resonators,optical sensing
更新于2025-09-23 15:21:01
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Confined whispering-gallery mode in silica double-toroid microcavities for optical sensing and trapping
摘要： We propose and theoretically study a silica double-toroid microcavity to confine the whispering-gallery mode (WGM) in an ultra-small space, which consists of two toroid-to-toroid coupled cavities separated by a nanoscale gap region with low refractive index, such as the air gap. Benefitting from the strong field localization of the “slot” effect, power enhancement of symmetric WGMs in the gap results in the ultra-small mode volume of 4.8 μm3, which is quite smaller than the conventional toroidal microcavity with mode volume of about hundreds of cubic micrometers. The confined modes hold the potential advantages over conventional photonic devices, especially in the applications of the sensing and optical trapping. In the application of refractometer, a high refractive index sensitivity of up to 468 nm per refractive index unit (nm/RIU) can be obtained in the 1000 nm wavelength band. In the optical trapping application, the double-toroid microcavity enables a significant field enhancement in the confined WGM, and the gradient force could reach as high as 22 pN/W for a single nanoparticle with the radius of 5 nm. As the potential advantages, this study of silica double-toroid microcavity provides a good reference for realizing the high-efficient photonic applications such as optical sensing and trapping.
关键词： optical sensing,refractometer,silica double-toroid microcavity,gradient force,optical trapping,whispering-gallery mode
更新于2025-09-23 15:21:01
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Analysis of a Single Solid Core Flat Fiber Plasmonic Refractive Index Sensor
摘要： In this article, a single solid core flat fiber (SSCFF) refractive index sensor based on surface plasmon resonance (SPR) is proposed and analyzed numerically using the finite element method (FEM). The proposed flat fiber consists of a single array of five circular holes. Among them the central hole is made of GeO2-doped silica which is forming the core. Other holes are filled with air and situated symmetrically on both sides of the central solid core. The upper flat surface of the fiber is coated with a thin plasmonic gold layer which is protected by an active titanium dioxide layers. Analyte is situated on top of these layers. The wavelength interrogation technique is applied to study the coupling characteristics between the core-guided mode and the surface plasmon mode as well as for the refractive index measurement. Numerical analysis results show that this sensor is able to detect high refractive index analytes from 1.49 to 1.54 with a good linear response. Additionally, the dependence of surface plasmonic resonance wavelength on analyte refractive index is studied. The maximum wavelength sensitivity of this sensor is found to be 4782 nm/RIU with a high resolution of 2.09 × 10?5 RIU. The effects of different structural parameters on loss spectrum are studied in detail to optimize this SSCFF structure. In comparison to traditional PCF, this SSCFF structure is fabrication complexity free as well as a suitable candidate for developing portable devices and high refractive index analyte sensors, particularly chemical and protein sensors.
关键词： Photonic crystal fiber,Surface plasmon,Optical sensing,Finite element method,Refractive index sensor
更新于2025-09-23 15:19:57
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On the combination of luminescent rare earth MOF and rhodamine dopant with two sensing channels for picric acid
摘要： The present paper reported a hybrid structure for the optical recognition of PA (picric acid). This dye-MOF structure, named as R6h@EuBTC, consisted of a supporting matrix based on rare earth MOF and a sensing probe based on rhodamine dye, which was con?rmed using XRD, IR, thermal and photophysical analysis. R6h@EuBTC's rhodamine absorption in visible region was enhanced by increasing PA concentrations, showing obvious color change and consequently colorimetric sensing. R6h@EuBTC's rhodamine emission component was increased by increasing PA concentrations, while its Eu emission component was slightly quenched by increasing PA concentrations, which offered self-calibrated sensing signals for ratiometric ?uorescent sensing. Linear response and good selectivity were observed for both sensing channels with LOD of 3.9 μM. R6h@EuBTC's sensing mechanism towards PA was the combination of two procedures, which were the emission turn on effect of rhodamine component triggered by PA-released protons and the emission turn off effect of Eu component caused by its electron transfer procedure to PA, respectively. R6h@EuBTC's novelty was its two sensing channels and the practicability of naked eye detection.
关键词： Ratiometric sensing,Optical sensing,Explosive detection,Naked eye detection
更新于2025-09-19 17:15:36
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Spectrophotometric, fluorimetric and electrochemical selective pyrophosphate/ATP sensing based on the dimethyltin(IV)-tiron system
摘要： Sensing of pyrophosphate anion (PPi) in the presence of nucleotide triphosphates allows the real time monitoring of the polymerase chain reaction. To get a deeper understanding of the factors involved in PPi/nucleotide triphosphate discrimination, a detailed study on the performance of a dimethyltin(IV)-catecholate complex capable of both separate fluorimetric or electrochemical detection of PPi in the presence of adenosine triphosphate (ATP) has been undertaken. Dimethyltin(IV) tightly binds PPi or ATP, and forms a stable 1:1 complex with tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid) in water. The complexation equilibria with all components are characterized quantitatively by potentiometric and spectroscopic titrations. Pyrophosphate anion can be detected owing to its ability to release free tiron from the complex by measuring either a fluorimetric or an electrochemical signal. On the contrary, ATP does not displace tiron but causes an interference with PPi in the fluorimetric detection method due to the formation of a ternary Me2Sn(IV)-tiron-ATP complex with optical properties intermediate between those of free and bound tiron. In the electrochemical (square wave voltammetry) method, the ternary ATP complex shows a separate peak which does not coincide with the peaks of neither free nor bound tiron, thus making possible the simultaneous detection of ATP in addition to PPi.
关键词： optical sensing,dimethyltin(IV),pyrophosphate,electrochemical sensing,adenosine triphosphate selectivity,tiron
更新于2025-09-19 17:15:36
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The influence of molecular structure on collision radius for optical sensing of molecular oxygen based on cyclometalated Ir( <scp>iii</scp> ) complexes
摘要： Three triphenylamine (TPA) substituted cyclometalated Ir(III) complexes IrA1, IrA2, and IrA3 based on Ir(ppy)3 were synthesized and applied as phosphorescent probes for the monitoring of molecular oxygen. The phosphorescence intensity of all the Ir(III) complexes in tetrahydrofuran (THF) was gradually quenched with an increase of oxygen concentration. The increase of TPA substituents on the meta-position of 2-phenylpyridine (IrA1-IrA3) gradually improved the oxygen sensitivity of cyclometalated Ir(III) complexes. IrA3 showed the highest oxygen sensitivity in THF with a KappSV of 204.8 bar?1 and a limit of detection (LOD) of 0.27 mbar. The relationship between molecular structure and the collision radiuses (s) of all the Ir(III) complexes has been investigated on the basis of the Demas model and the fundamental expression of luminescence quenching systems by oxygen. The ratio of collision radiuses are sIrA1/sIr(ppy)3 = 1.27 ± 0.05, sIrA2/sIr(ppy)3 = 1.72 ± 0.10, and sIrA3/sIr(ppy)3 = 2.13 ± 0.07, respectively. The introduction and increase of TPA substituents can obviously increase the collision radiuses of cyclometalated Ir(III) complexes which leading to potential oxygen sensitivity. And the incremental effect of collision radiuses caused by the introduction of TPA substituents resulted in outstanding oxygen sensitivity of IrA3. The results demonstrate for the first time evidence between molecular structure and oxygen sensitivity of the emitters for optical sensing.
关键词： optical sensing,collision radius,molecular oxygen,triphenylamine substituents,cyclometalated Ir(III) complexes
更新于2025-09-19 17:15:36