Gas refractometry using hollow core photonic bandgap fiber

Over the last two decades, much research has been carried out on sensors based on photonic crystal fibers. Their unique structure comprising of a periodic array of air holes running along their length provides optical properties that are highly suited for refractometer sensors. The thesis presents a fiber-optic interferometric gas refractometer which is capable of spectrally resolved measurements of both real and imaginary parts of the complex refractive index. The refractometer is based on an earlier fiber based Mach-Zehnder-type refractometer design that was used to determine the refractive index of air-acetylene mixture. The aim of the thesis was to improve the device design in order to ascertain the refractive index of pure acetylene. The device adopts a hollow-core photonic bandgap fiber as both a sample cell and a waveguide. This provides the best overlap between probing light and the analyte. In addition, it requires a very small volume of the analyte due to the small dimensions of the fiber, and the sample cell can be made long while keeping the device compact. The complex refractive index of approx. 96 percent pure acetylene was measured within the optical C band where the gas has a number of pronounced resonance frequencies. The measurement was repeated in approx. 500 Pa air and was used as reference for interpreting the results for acetylene. The optical absorption and refractive index change of acetylene over the resonance frequencies were analyzed and its absorption coefficient and refractive index were calculated. The demonstrated capability of this device to measure the real and imaginary parts of the refractive index of an analyte has important implications in the sensor industry

Development of a sensor for the continuous measurement of oil concentration in a refrigeration system

Shortcomings in the present standard method of determining the circulating oil concentration in a refrigeration system have led to the current research, wherein a continuous, in-line method of measuring the flowing oil concentration is sought;A literature survey and preliminary property measurements examined properties of oil-refrigerant mixtures that could be measured to infer the oil concentration in the liquid line of a refrigeration system. Four measurement methods were selected for development into oil concentration sensors: a vibrating U-tube densimeter, a new type of in-line viscometer, a prototype acoustic velocity probe, and an optical fiber refractometer;A flow loop capable of simulating a wide variety of liquid-line conditions was constructed for the testing and calibration of the oil concentration sensors. Performance tests of the densimeter, viscometer, and acoustic velocity sensor were conducted over an oil concentration range of 0 to 30 weight-percent for 150 SUS naphthenic oil/R-12, 150 SUS naphthenic oil/R-22, and 150 SUS alkylbenzene oil/R-502 mixtures. The temperatures in the flow loop test section during the performance tests were varied from 70 to 120 F and the pressure was maintained to provide approximately 3 F subcooling. Performance testing of the refractometer was not completed because of severe probe temperature sensitivity and poor repeatability;The performance test results were statistically analyzed to determine the oil concentration measurement uncertainty. The three sensors tested were found to attain the desired ±1 weight-percent uncertainty under a variety of conditions. Application guidelines are presented for the use of the densimeter, viscometer, and acoustic velocity as oil concentration sensors

Fiber-optic and coaxial-cable extrinsic Fabry-Perot interferometers for sensing applications

”The fiber-optic extrinsic Fabry-Perot interferometer (EFPI) is one of the simplest sensing configurations and is widely used in various applications due to its prominent features, such as high sensitivity, immunity to electromagnetic interference, and remote operation capability. In this research, a novel one-dimensional wide-range displacement sensor and a three-dimensional displacement sensor based on fiber-optic EFPIs are demonstrated. These two robust and easy-to-manufacture sensors expand the application scope of the fiber-optic EFPI sensor devices, and have great potential in structural health monitoring, the construction industry, oil well monitoring, and geo-technology. Furthermore, inspired by the fiber-optic EFPI, a novel and universal ultra-sensitive microwave sensing platform based on an open-ended hollow coaxial cable resonator (OE-HCCR, i.e., the coaxial cable EFPI) is developed. Both the theoretical predictions and experimental results demonstrate the ultra-high sensitivity of the OE-HCCR device to variations of the gap distance between the endface of the coaxial cable and an external metal plate. Additionally, combining the chemical-specific adsorption properties of metal-organic framework (MOF) materials with the dielectric sensitivity of the OE-HCCR, a mechanically robust and portable gas sensor device (OE-HCCR-MOF) with high chemical selectivity and sensitivity is proposed and experimentally demonstrated. Due to its low cost, high sensitivity, all-metal structure, robustness, and ease of signal demodulation, it is envisioned that the proposed OE-HCCR device will advance EFPI sensing technologies, revolutionize the sensing field, and enable many important sensing applications that take place in harsh environments”--Abstract, page iv

Integrated Long period waveguide gratings for refractometric and gas sensing applications

Depuis plus d'une vingtaine d'année, la photonique intégrée est devenu un domaine de recherche très actif pour le développement de capteurs intégrés à hautes performances. Les capteurs chimiques intégrés, et en particulier ceux dédiés à la détection de gaz, font inexorablement l'objet d'une investigation poussée pour des raisons de santé publique ainsi que pour un grand nombre d'applications industrielles. Un problème majeur lié à la grande diversité des systèmes de capteurs proposés par la communauté scientifique survient toutefois: comment analyser les différentes architectures de façon précise et ainsi pouvoir les comparer? Dans un premier temps, cette thèse propose un modèle de classification pour les capteurs chimiques optiques, suivi d'une revue des architectures de photonique intégrée dédiées à la détection de gaz. Ensuite sont détaillés les modèles théoriques, la conception et le travail expérimental qui ont été effectués dans cette thèse pour la réalisation de capteurs réfractométriques intégrés sur silicium. En particulier, un type spécifique de structure réfractométrique semble être mis en avant par ce travail d'analyse de l'état de l'art, et a par conséquent été développé de façon plus approfondi; il s'agit des réseaux intégrés à longue période. Un modèle détaillé du mécanisme de couplage optique mis en jeux par les réseaux à longue période est par la suite développé. Ce modèle est basé sur la théorie des modes couplés pour laquelle une approche perturbatoire est employée pour analyser les propriétés réfractométriques de ces structures. En utilisant le modèle proposé, plusieurs versions de réseaux à longue période intégrés sont conçus, simulés, puis optimisés. C'est en contrôlant les superpositions de champs optiques au niveau des guides d'ondes ainsi que les propriétés dispersives des modes optiques qu'il est possible d'obtenir de hautes sensibilités de détection ainsi que des réponses spectrales adéquates. Ces réseaux intégrés à longue période ont ensuite été fabriqués à partir d'un procédé technologique de nitrure de silicium spécialement développé dans la salle blanche du LAAS. Puis ils ont été testés sur une station de charactérisation optique conçue dans cette thèse. Des sensibilités réfractométriques aussi hautes que 11,500 nm/RIU ont été expérimentalement obtenues et sont stables sur une large bande spectrale de 100 nm centrée sur 1550 nm, le tout avec une faible diaphonie en température de 0.15 nm/°C. De plus, en s'appuyant sur le modèle proposé, d'autres versions de réseaux à longue période intégrés démontrent via simulation la possibilité d'atteindre des sensibilités d'au moins 300,000 nm/RIU, sensiblités pour lesquelles les limites liées à la fabrications et à l'expérimentation sont abordées. Finalement, une structure de réseaux intégrés à longue période est employée pour la détection de CO2 en utilisant un film en polymère poreux: le PolyHexaMethylene Biguanide. En plus du très fort potentiel des réseaux intégrés à longue période qui a été démontré dans cette thèse avec les modèles proposés et à travers les résultats obtenus, nous pensons également que le travail détaillé ici pourrait également servir à la réalisation de capteurs encore plus performants, et potentiellement permettre l'émergence de nouvelles applications

Ultrasensitive plasmonic sensing in air using optical fibre spectral combs

Surface plasmon polaritons (SPP) can be excited on metal-coated optical fibres, enabling the accurate monitoring of refractive index changes. Configurations reported so far mainly operate in liquids but not in air because of a mismatch between permittivities of guided light modes and the surrounding medium. Here we demonstrate a plasmonic optical fibre platform that overcomes this limitation. The underpinning of our work is a grating architecture - a gold-coated highly tilted Bragg grating - that excites a spectral comb of narrowband-cladding modes with effective indices near 1.0 and below. Using conventional spectral interrogation, we measure shifts of the SPP-matched resonances in response to static atmospheric pressure changes. A dynamic experiment conducted using a laser lined-up with an SPP-matched resonance demonstrates the abil

An experimental study on the process monitoring of resin transfer molded composite structures using fiber optic sensors

This thesis focuses on the research conducted on in situ process monitoring (cure and flow) of resin transfer molded glass fiber reinforced polymer composites using Fiber Bragg Grating (FBG), etched bare fiber optic sensors and Fresnel refractometers. In this direction, a laboratory scale resin transfer molding (RTM) apparatus was used with the capability of visually monitoring the resin filling process as well as embedding fiber optic sensors. Both FBG and etched fiber sensors are embedded into glass fiber rein-forcements in the RTM mold, and are used to monitor the flow front during the resin injec-tion and subsequently the cure cycle. Moreover, the cure cycle of the resin system utilized in this work is studied using an in-house developed Fresnel based refractometer. The data gathered from corresponding cure monitoring experiments have been compared with the results of polymer extraction experiments and excellent correlation between the results was observed. The embedded FBG sensors also allow the determination of mechanical stresses or loads on the in- service composite parts, through interrogating these sensors. This process is referred to as Structural Health Monitoring, which is not considered within the scope of this thesis work

Advances in Fiber-Optic Extrinsic Fabry-Perot Interferometric Physical and Mechanical Sensors: A Review

Fabry-Perot Interferometers Have Found a Multitude of Scientific and Industrial Applications Ranging from Gravitational Wave Detection, High-Resolution Spectroscopy, and Optical Filters to Quantum Optomechanics. Integrated with Optical Fiber Waveguide Technology, the Fiber-Optic Fabry-Perot Interferometers Have Emerged as a Unique Candidate for High-Sensitivity Sensing and Have Undergone Tremendous Growth and Advancement in the Past Two Decades with their Successful Applications in an Expansive Range of Fields. the Extrinsic Cavity-Based Devices, I.e., the Fiber-Optic Extrinsic Fabry-Perot Interferometers (EFPIs), Enable Great Flexibility in the Design of the Sensitive Fabry-Perot Cavity Combined with State-Of-The-Art Micromachining and Conventional Mechanical Fabrication, Leading to the Development of a Diverse Array of EFPI Sensors Targeting at Different Physical Quantities. Here, We Summarize the Recent Progress of Fiber-Optic EFPI Sensors, Providing an overview of Different Physical and Mechanical Sensors based on the Fabry-Perot Interferometer Principle, with a Special Focus on Displacement-Related Quantities, Such as Strain, Force, Tilt, Vibration and Acceleration, Pressure, and Acoustic. the Working Principle and Signal Demodulation Methods Are Shown in Brief. Perspectives on Further Advancement of EFPI Sensing Technologies Are Also Discussed

Optical Gas Sensing: Media, Mechanisms and Applications

Optical gas sensing is one of the fastest developing research areas in laser spectroscopy. Continuous development of new coherent light sources operating especially in the Mid-IR spectral band (QCL—Quantum Cascade Lasers, ICL—Interband Cascade Lasers, OPO—Optical Parametric Oscillator, DFG—Difference Frequency Generation, optical frequency combs, etc.) stimulates new, sophisticated methods and technological solutions in this area. The development of clever techniques in gas detection based on new mechanisms of sensing (photoacoustic, photothermal, dispersion, etc.) supported by advanced applied electronics and huge progress in signal processing allows us to introduce more sensitive, broader-band and miniaturized optical sensors. Additionally, the substantial development of fast and sensitive photodetectors in MIR and FIR is of great support to progress in gas sensing. Recent material and technological progress in the development of hollow-core optical fibers allowing low-loss transmission of light in both Near- and Mid-IR has opened a new route for obtaining the low-volume, long optical paths that are so strongly required in laser-based gas sensors, leading to the development of a novel branch of laser-based gas detectors. This Special Issue summarizes the most recent progress in the development of optical sensors utilizing novel materials and laser-based gas sensing techniques

Integrated Additive and Subtractive Manufacturing of Glass Photonic Sensors for Harsh Environment Applications

Research and development in advanced manufacturing for sensors and devices fabrication is continuously changing the world, assisting to giving sensing solutions in the physical, chemical and biological fields. Specifically, many modern engineered systems are designed to operate under extreme conditions such as high temperature, high pressure, corrosion/erosion, strong electromagnetic interference, heavy load, long reaching distance, limited space, etc. Very often, these extreme conditions not only degrade the performance of the system but also impose risks of catastrophic failures and severe consequences. To perform reliably under these harsh conditions, the materials and components need to be properly monitored and the systems need to be optimally controlled. However, most existing sensing technologies are insufficient to work reliably under these harsh conditions. Innovations in sensor design, fabrication and packaging are needed to address the technological challenges and bridge the capability gaps. Optical fiber sensors have been widely researched and developed for energy, defense, environmental, biochemical and industry sensing applications. In general, optical fiber sensors have a number of well-known advantages such as miniature in size, high sensitivity, long reaching distance, capability of multiplexing and immunity to electromagnetic interference (EMI). In addition, optical fiber sensors are capable of operating under extreme environment conditions, such as high temperature, high pressure, and toxic/corrosive/erosive atmospheres. However, optical fiber sensors are also fragile and easy to break. It has been a challenging task to fabricate and package optical fiber sensors with predicable performance and desired reliability under harsh conditions. The latest advancements in high precision laser micromachining and three-dimensional (3D) printing techniques have opened a window of opportunity to manufacture new photonic structures and integrated sensing devices that deliver unprecedented performance. Consequently, the optical sensor field has quietly gone through a revolutionary transition from the traditional discrete bulk optics to today’s devices and structures with enhanced functionalities and improved robustness for harsh environment applications. Driven by the needs for sensors capable of operating in harsh environments, integrated additive and subtractive manufacturing (IASM) for glass photonics sensor fabrication process has been proposed and developed. In this dissertation, a series of high-performance optical fiber sensors were proposed and fabricated. In addition, several significant sensing measurements (e.g., pressure, temperature, refractive index variation) of the proposed sensors and structures with enhanced robustness were demonstrated in this dissertation. To realize measurement of above parameters, different working principles were studied, including mechanical deflection, light-material interaction and utilizing properties of fluidics. The sensing performance of the fabricated sensors and structures were characterized to demonstrate the capabilities of the developed IASM process on advanced manufacturing of glass photonic sensors with specific geometry and functions, and the realization for information integrated manufacturing purpose