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

Coaxial Cable Sensors Based on Fabry-Perot Interferometers and Their Applications in Distributed Sensing

Aging civic infrastructures in the world has put tremendous pressure in their maintenances because potential failure of the large size civil structures will be catastrophic. Structure health monitoring (SHM) has been proven effective to prevent these failures, and distributed sensing technologies are preferred in SHM as they are effective to provide comprehensive evaluation of the structures. Fiber optic sensors are well developed in the past two decades for distributed sensing, but the lack of robustness and the limited deformability of silica make them not suitable for heavy duty and large deformation applications, which is very common in SHM. To address the above limitation of optical fiber sensors, we change the sensing platform from optical fibers to coaxial cable. Inspired by optical FPI, we created two reflectors on a coaxial cable to form a coaxial cable Fabry-Perot interferometer (CCFPI). The reflectors are commonly made by drilling half way holes or crimp on the cable, which introduce impedance discontinuity and hence partial reflection of EM wave in the cable. The two reflectors can produce interference patterns with multiple resonant frequencies which can be tracked to indicate changes in physical parameters such as temperature and strain. To realize distributed sensing, multiple reflectors are implemented along a coaxial cable, where every two consecutive reflectors will form a low finesse CCFPI. A specific signal process technique is used to reconstruct each individual CCFPI interferogram from the complex frequency domain signal. As examples of the distributed sensing capability of the coaxial cable platform, distributed torsion sensing and 3D beam shape estimation system are demonstrated in this thesis. By modifying the cable material and structure, we can achieve other special function for CC-FPI sensors. By fabricating the cable with ceramics as dielectric material and implanting built in reflectors, a high temperature CC-FPI sensor is developed and tested. Another example is a magnetic field sensor made by filling a cavity in a semi-rigid cable with ferrofluid. When external magnetic field change, the property of the ferrofluid will also change, resulting in spectrum shift of the FPI. The coaxial cable FPI sensors have many potentials to measure different physical parameters in distributed sensing form, which makes it a very good sensing platform for long distance and distributed sensing in harsh environment and heavy duty applications

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

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

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

OPTICAL AND OPTOMECHANICAL RESONATORS AND THEIR APPLICATIONS IN COMMUNICATION AND SENSING

The radiation pressure of the large circulating optical power inside micro-scale high quality factor Whispering-Gallery mode micoresonators couples the mechanical deformation of the resonator structure to the optical resonance. This coupling results in damping or amplification of the corresponding mechanical modes. Self-sustained mechanical oscillation takes place when the optomechanical gain becomes larger than mechanical loss. In this dissertation, several applications of optomechanical oscillator (OMO) in communication and sensing are proposed and explored using silica microtoroid resonator. First we investigate the spectrum of the OMO and define weak\u27 and \u27strong\u27 harmonic generation regimes based on two distinct spectral behaviors. In weak harmonic regime, an analytical method is proposed to optimize the spectral behavior of an OMO for RF-photonic communication systems. In the strong harmonic regime, we show that OMO spectrum can be used in a read-out system for resonant optical sensing applications. Next, we explore optomechanical RF mixing and its application in RF-photonics. We study optomechanical RF mixing using coupled differential equations as well as a semi-analytical model that simplifies the calculation of mixed frequency components. Furthermore, optomechanical down-conversion of various waveforms and audio signal from an RF carrier are demonstrated. Here for the first time we show that an OMO can function as a high-resolution mass sensor based on optomechanical oscillation frequency shift. In an OMO based mass sensor, optical power simultaneously servers as an efficient actuator and a sensitive probe for monitoring optomechanical oscillation frequency variations. The narrow linewidth of optomechanical oscillation and the small effective mass of the corresponding mechanical mode result in sub-pg mass sensitivity. We analyze the performance of microtoroid OMO mass sensor and evaluate its ultimate detection limit. The outcomes of our study enable combination of resonant optical sensing with optomechanical sensing in a single device. This so-called \u27dual-mode\u27 sensing can be a powerful technique for measuring the properties (mass, density and refractive index) of micro/nano-particles and molecules. To boost the optical sensitivity of the dual-mode sensor, we also demonstrate a dynamic sensing method where the resonant photonic sensitivity is improved by over 50 times through thermally induced line narrowing

Effects of the environment on quantum systems: decoherence, bound states and high impedance in superconducting circuits

Superconducting circuits in the quantum regime represent a viable platform for microwave quantum optics, quantum simulations and quantum computing. In the last two decades, a large effort brought this architecture from an academic curiosity to concrete technology.\ua0 In this thesis, we study the effects of the environment on superconducting circuits. We consider mainly two typologies of the environment. On one hand, we study the classical baths inevitably coupled to the circuits, in particular the substrate where they are fabricated and the highly attenuated coaxial lines used for controlling them, which are the main sources for decoherence. On the other hand, we study structured electromagnetic environments that shape the density of states for the circuits, modifying their energy structure and their excitation properties.\ua0\ua0 Defects on the substrate mechanically and electrically coupled to superconducting circuits, behave as a bath of two-level systems. We investigate the effects of the bath on a qubit fabricated on silicon. From a time trace with more than 2000 measurements of T1 and T2 (every 3 min for 60 h), we statistically infer a Lorentzian resonance signature of the bath. Moreover, measuring the residual population of the first excited state of the qubit, and tuning the photonic population in the line, we assess the thermal state of the bath, measuring a temperature of 56 mK. Furthermore, we investigate the mechanical coupling of the bath, saturating its state, strongly pumping neighbouring modes in a high finesse mechanical resonator. On a piezoelectric substrate, the travelling phonons, carry an electric component together with a lattice deformation. Therefore, superconducting circuits can be coupled to a phononic waveguide through which they release part of their energy. We design, fabricate and measure superconducting resonators on gallium arsenide, demonstrating the electromechanical coupling as the main source of decoherence.\ua0Concentrating on the effects of the photonic bath in the coaxial line, we design a qubit with a very large coupling to this bath compared to the bath of two-level fluctuators. In this limit, the scattering of a coherent photon by the qubit linearly depends on the photonic bath population. In this regime, the qubit can be used as a primary thermometer; we measured injected calibrated noise and the photon occupation of our input lines at different temperatures.\ua0 Finally, we implemented a slow-waveguide made of a linear chain of high impedance resonators. The excitation of two transmon qubits coupled to the waveguide is dressed with a photonic component, generating the hybrid excitation of atom-photon bound state. We spectroscopically investigated the first and second excitation subspaces of the system, and we demonstrated full frequency and time domain control, of these bound states. These results may help to improve the performance of superconducting circuits and their setup. Moreover, we hope that our experiment can provide tools for quantum thermodynamics and quantum simulation