NOVEL SENSOR PLATFORMS BASED ON FABRY-PEROT RESONATORS FOR APPLICATIONS IN ENVIRONMENTAL GEOPHYSICS

Fabry-Perot resonator sensors have been widely used for various physical and chemical measurements owing to their unique advantages over traditional sensors such as high measurement resolution, mechanically robust, and distributed sensing capabilities. This dissertation focuses on the development of robust fiber optic microwave sensors based on Fabry-Perot resonator mechanism for real-time applications in environmental geophysics. Firstly, a novel Extrinsic Fabry-Perot Interferometer (EFPI)-based fiber-optic sensor for force measurement using a pre-buckled beam was demonstrated. The axial displacement is transferred and amplified to a horizontal deflection at the middle of the buckled beam, leading to a relatively significant change in the Fabry-Perot cavity length. The force measurement range and the size of the sensor can be easily reconfigured by adjusting the size of the beam, enabling force measurement for different scenarios. Secondly, a self-compensated inclinometer with a wide dynamic range and high measurement resolution based on two hollow coaxial cable Fabry-Perot resonators (HCC-FPRs) was reported. By tracking the shift of the resonance wavelength of the HCC-FPR, two HCC-FPRs are used in the inclinometer design, which enables the inclinometer to achieve self-compensation for variations in environmental factors. Thirdly, a Polyvinyl Alcohol (PVA) film-assisted open-ended hollow coaxial cable Fabry-Perot resonator was proposed for highly sensitive embeddable soil moisture measurements. The invented sensor platform could be reconfigured to detect chemical contaminants in soil by changing the functional films in the active zone of the sensor --Abstract, p. i

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

Instability Risk and Beam Profile Variation in Optical Ring Resonator due to Thin Gradient Index Lens

In this study, a simple ring resonator model in presence of thin gradient index (GRIN) lens is investigated to characterize the optical beam maginification quality beyond its traditional modalities. This model allow us to vary and control the limit of resonator stability more significantly.It consist of two folding arms and each arm can be realized by its cavity components. Insertation of thin GRIN lens ( thickness < 9.3mm) in ring resonator, mainly in between first folding range gives the magnified output beams and meets the beam expander feature for the laser. Variation of GRIN lens thickness (L) is an emphatic and influencing parameter than its refractive index (n) to disturb the resonator stability. Resonator stability in Tangential (T) plane is relatively more sensitive than sagittal (S) plane. Vigorous magnification in optical beam size at the end of output range in a cavity is the noticeable consequences because of GRIN lens

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

Femtosecond Laser Micromachining of Advanced Fiber Optic Sensors and Devices

Research and development in photonic micro/nano structures functioned as sensors and devices have experienced significant growth in recent years, fueled by their broad applications in the fields of physical, chemical and biological quantities. Compared with conventional sensors with bulky assemblies, recent process in femtosecond (fs) laser three-dimensional (3D) micro- and even nano-scale micromachining technique has been proven an effective and flexible way for one-step fabrication of assembly-free micro devices and structures in various transparent materials, such as fused silica and single crystal sapphire materials. When used for fabrication, fs laser has many unique characteristics, such as negligible cracks, minimal heat-affected-zone, low recast, high precision, and the capability of embedded 3D fabrication, compared with conventional long pulse lasers. The merits of this advanced manufacturing technique enable the unique opportunity to fabricate integrated sensors with improved robustness, enriched functionality, enhanced intelligence, and unprecedented performance. Recently, fiber optic sensors have been widely used for energy, defense, environmental, biomedical and industry sensing applications. In addition to the well-known advantages of miniaturized in size, high sensitivity, simple to fabricate, immunity to electromagnetic interference (EMI) and resistance to corrosion, all-optical fiber sensors are becoming more and more desirable when designed with characteristics of assembly free and operation in the reflection configuration. In particular, all-optical fiber sensor is a good candidate to address the monitoring needs within extreme environment conditions, such as high temperature, high pressure, toxic/corrosive/erosive atmosphere, and large strain/stress. In addition, assembly-free, advanced fiber optic sensors and devices are also needed in optofluidic systems for chemical/biomedical sensing applications and polarization manipulation in optical systems. Different fs laser micromachining techniques were investigated for different purposes, such as fs laser direct ablating, fs laser irradiation with chemical etching (FLICE) and laser induced stresses. A series of high performance assembly-free, all-optical fiber sensor probes operated in a reflection configuration were proposed and fabricated. Meanwhile, several significant sensing measurements (e.g., high temperature, high pressure, refractive index variation, and molecule identification) of the proposed sensors were demonstrated in this dissertation as well. In addition to the probe based fiber optic sensors, stress induced birefringence was also created in the commercial optical fibers using fs laser induced stresses technique, resulting in several advanced polarization dependent devices, including a fiber inline quarter waveplate and a fiber inline polarizer based on the long period fiber grating (LPFG) structure

LASER Tech Briefs, Spring 1994

Topics in this Laser Tech Brief include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Mechanics, Fabrication Technology, and books and reports

Permanently-Installed Distributed Pressure Sensors for Downhole Applications

Technology advancements (e.g., hydraulic fracturing and horizontal drilling) to recover unconventional oil and gas (UOG) resources are critical in maintaining future U.S. oil and gas production levels. Permanently installed distributed downhole pressure sensors could monitor fracture propagation, assess the effectiveness of hydraulic fracturing, and optimize hydraulic fracturing placement so that overall UOG recovery efficiency can be increased. However, the harsh environment (high temperatures, high pressures, strong vibration, and presence of brine, mud, debris, hydrate, and various gases), the long data telemetry distance, and the requirements of reliability and service lifetime make the downhole monitoring a very challenging task. To combat these challenges, this thesis presents three sensing systems for downhole pressure monitoring. First, A microwave-photonic low-coherence interferometry (MPLCI) system is proposed for optical fiber based distributed sensing. The system can be used to interrogate the intrinsic Fabry–Pérot interferometers (IFPIs) based distributed downhole pressure sensors. Assisted by an unbalanced Michelson interferometer (MI), a low-coherence laser source is used to interrogate IFPIs along with an optical fiber for a dark zone-free (or spatially continuous) distributed measurement. By combining the advantages of microwaves and photonics, the MPLCI system can synergistically achieve high sensitivity and high spatial resolution. Second, to solve the packaging and drift problems in optical fiber sensors, an all-digital sensing method based on an electrical encoder is developed for downhole pressure monitoring. The key innovation of the all-digital sensor concept is the built-in nonelectric analog-to-digital converter (ADC), which eliminates the need for downhole electronics for signal conditioning and telemetry in conventional electrical downhole sensors. As such, the sensors are more robust, less expensive, and have less drift in comparison with the existing sensors. Because the sensor outputs are digital in nature, the developed sensors can be remotely logged over a long distance, and many sensors can be digitally multiplexed for distributed sensing using a single surface instrument. The all-digital pressure sensors and their surface instrument were designed, engineered, fabricated, and calibrated. The integrated sensing system was tested/validated at both laboratory and research wellbores. Third, to solve the hysteresis problem induced by the electrical encoder, a non-contact optical encoder based all-digital pressure sensor for downhole applications is proposed. The proposed sensor combines the advantages of both optical fiber and all-digital sensing method. The noncontact-type encoder, which is composed of an encoding pad and an all-glass optical fiber sensing head. A glass additive and subtractive manufacturing (ASM) system was used to embed the multi-channel optical fibers into a bulk-fused silica glass substrate with high positioning accuracy and good thermal stability even at elevated temperatures. The optical fiber only serves as the telemetry channel to directly transmit the data in digital format, such that the system has long-distance telemetry capability as well as low drift. The proposed pressure sensor was manufactured and experimentally verified to have a high SNR, linear pressure response, and good long-term stability. In addition, a mathematical model to study the relationships between the sensor’s performances and design parameters was established

Optical Fiber Sensing for SubMillimeter IntrinsicallySafe Liquid Level Monitoring

The popularization and fast growth of the optical fiber sensing technology has stimulated in different fields WHERE measurements of diverse physical and chemical parameters are required. Among these parameters, liquid level sensing plays an essential role in industry applications such as chemical processing, fuel storage, transportation systems, oil tanks/reservoirs, and wastewater treatment plants. In order to measure this parameter different sensing techniques based on acoustical, mechanical, electrical and electromagnetical technologies have been already proposed. Nevertheless, they suffer from intrinsic safety concerns in harsh environments, especially with corrosive, and explosive or flammable atmospheres. Fiber optic based liquid level sensors (FOLLS) can work in harsh environments with inherent advantageous features that only optical fiber offers, such as intrinsic safety, resistance to chemical corrosion, immunity to electromagnetic interference, electric isolation, small size, lightweight sensing heads, high accuracy and resolution, easy multiplexing, and capability for extremely remote monitoring without the need of electrical power at the measuring point. In this context, this doctoral Thesis presents two specific optical fiber sensor technologies to measure liquid level. Both the MachZehnder and FabryPerot interferometers are researched. The Thesis also focus on uniform fiber Bragg grating (FBG). Since these technologies have different operation principle, the liquid level measurement was based on refractive index changes for the MachZehnder sensor and based on hydrostatic pressure in the case of both the FPI and FBG sensors. Furthermore, analysis of temperature crosssensitivity is performed with the aim to improve the pressurebased sensors performance. Despite the FBGs provide high accurate measurements, the interrogation systems are the most important drawback for their large commercial application, due to their high cost. Therefore, a new and lower cost interrogation technique based on FPI microcavities was proposed as a final contribution

Simulations of Optical Effects in Nanostructures

Thesis advisor: Krzysztof KempaIn my work presented in this dissertation, I have focused on simulation studies of light interaction with nanostructures made of metals and dielectrics. Of particular interest have been plasmonic effects. The structures included the wire and coaxial nanowaveguides, as well as periodic arrays of planar quasi-triangles, and periodic arrays of nanoholes in thin metallic films. In the nanowaveguides I focused on plasmon polariton modes which resemble the TEM modes propagating in the corresponding conventional radio transmission lines. This collaborative research, involving an experimental effort, showed how the nanoscopic plasmon polariton modes reduce in the retarded limit to the TEM modes, and in the non-retarded limit to the corresponding surface plasmon modes. My simulations explained details of recent experimental results involving plasmonic waveguiding in metallic nanowires. Similar results have been obtained for nanocoaxial waveguides. My simulations of the optical absorption in the arrays of nano quasi-triangles, recently observed experimentally, helped identify those as due to Mie plasmonic resonances in these nanoparticles. They also explained the peak shifts in terms of the 2D surface plasmon dispersion, and the plasmon momentum quantization. In the study of the arrays evolution from holes to quasi-triangles, my simulations provided the clue to the critical behavior of the peak position for structures approaching the percolation threshold (the transitional structure in the series, for which film resistance diverges), and allowed to identify the series of structures as an analog of the percolation threshold problem. Finally, I have simulated optical performance of nanorod arrays (or multi-core nanocoax), which have been employed as platform for novel solar cells. My simulations have been employed to predict and optimize these cells. My work resulted in 5 publications and 2 manuscripts in preparation.Thesis (PhD) — Boston College, 2011.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Physics

NASA Patent Abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 21) Abstracts

Abstracts are cited for 87 patents and applications introduced into the NASA scientific and technical information system during the period of January 1982 through June 1982. Each entry consists of a citation, an abstract, and in mose cases, a key illustration selected from the patent or patent application