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

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

A review of single-mode fiber optofluidics

We review the field we describe as “single-mode fiber optofluidics” which combines the technologies of microfluidics with single-mode fiber optics for delivering new implementations of well-known single-mode optical fiber devices. The ability of a fluid to be easily shaped to different geometries plus the ability to have its optical properties easily changed via concentration changes or an applied electrical or magnetic field offers potential benefits such as no mechanical moving parts, miniaturization, increased sensitivity and lower costs. However, device fabrication and operation can be more complex than in established single-mode fiber optic devices

Glassy Materials Based Microdevices

Microtechnology has changed our world since the last century, when silicon microelectronics revolutionized sensor, control and communication areas, with applications extending from domotics to automotive, and from security to biomedicine. The present century, however, is also seeing an accelerating pace of innovation in glassy materials; as an example, glass-ceramics, which successfully combine the properties of an amorphous matrix with those of micro- or nano-crystals, offer a very high flexibility of design to chemists, physicists and engineers, who can conceive and implement advanced microdevices. In a very similar way, the synthesis of glassy polymers in a very wide range of chemical structures offers unprecedented potential of applications. The contemporary availability of microfabrication technologies, such as direct laser writing or 3D printing, which add to the most common processes (deposition, lithography and etching), facilitates the development of novel or advanced microdevices based on glassy materials. Biochemical and biomedical sensors, especially with the lab-on-a-chip target, are one of the most evident proofs of the success of this material platform. Other applications have also emerged in environment, food, and chemical industries. The present Special Issue of Micromachines aims at reviewing the current state-of-the-art and presenting perspectives of further development. Contributions related to the technologies, glassy materials, design and fabrication processes, characterization, and, eventually, applications are welcome

Tapered optical fibre sensors: current trends and future perspectives

The development of reliable, affordable and efficient sensors is a key step in providing tools for efficient monitoring of critical environmental parameters. This review focuses on the use of tapered optical fibres as an environmental sensing platform. Tapered fibres allow access to the evanescent wave of the propagating mode, which can be exploited to facilitate chemical sensing by spectroscopic evaluation of the medium surrounding the optical fibre, by measurement of the refractive index of the medium, or by coupling to other waveguides formed of chemically sensitive materials. In addition, the reduced diameter of the tapered section of the optical fibre can offer benefits when measuring physical parameters such as strain and temperature. A review of the basic sensing platforms implemented using tapered optical fibres and their application for development of fibre-optic physical, chemical and bio-sensors is presented

Developing Integrated Optofluidic Platforms for Cellular Phenotyping.

This research demonstrates two optofluidic platforms to address three major problems of current fluorescence-based optical detection methods for cellular phenotyping: (1) limited number of fluorescent probes, (2) laborious and time-consuming assay preparation and manipulation steps, and (3) compromised sensing performance in a point-of-care setting. The first optofluidic platform is called the “microfluidic multispectral flow cytometry (MMFC) device”. The function of the MMFC device is to discriminate multiple cell types based on their fluorescent proteins or surface biomarkers at single cell level with a simplified optical setup. It represents a unique class of optofluidic system incorporating a MEMS-based tunable nanoimprinted grating microdevice, a single excitation laser, and a single PMT detector. The system enables us to achieve in-situ continuous spectral profile detection for bioparticles flowing in a microfluidic channel with high specificity and high speed. The second optofluidic platform is called the “microfluidic immunophenotyping assay (MIPA) device”. The function of the MIPA device is to achieve on-chip cell trapping, cell stimulation and in-situ secreted cytokine detection in one single chip with a shorten assay time and less sample requirements. Compared to previous studies using heterogeneous immunoassay techniques and requiring a longer assay time due to multiple surface immobilization processes and washing steps, our immunophenotyping assay with the MIPA device holds significant promise to open ways for rapid immune status determination in real clinical settings.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/97933/1/nthuang_1.pd

Pós-processamento de fibras óticas para aplicações de sensores

In this work optical fiber post-processing techniques are proposed in order to produce optical fiber sensors (OFS) with lower costs, simplicity and with competitive characteristics compared with their counterparts. The first device was based on multimode interferometers. Those were fabricated by fusing multimode (MM) glass silica fibers (GOF) and MM polymer optical fibers (POF) between two single mode GOFs. For the GOF-based sensor, it was obtained a sensitivity of 4.6 pm/bar. Regarding the POF-based multimodal interferometer, a sensitivity of 58 pm/bar was reached, which corresponds to an enhancement of the sensitivity of twelve times when compared to the one obtained for GOF. Additionally, this sensitivity is five times higher than the one obtained for the POF Bragg grating technology. This improvement in sensitivity makes this sensor very promising since it can reach higher resolutions. The second fiber optic sensor discussed in this work consisted of mechanically induced long period gratings. These were obtained through very simple fabrication methodologies, which consisted of a periodical distribution of photopolymerizable resin onto a single mode GOF, followed by chemical corrosion, which allowed to periodically modulate the fiber diameter. This production method is more advantageous than its direct rivals since it applies cheap and easy to reproduce production techniques and does not require the use of photolithography or chemical vapor deposition technologies. The characterization of this structure to external parameters, such as: longitudinal strain, displacement and temperature revealed promising capabilities, since they allowed, not only the wavelength tuning of the spectral band, but also the optical power coupling strength. The results were very promising, as far as the displacement characterizations are concerned, since a measurement range of 0 - 60 mm was obtained, which is larger than those reported in the literature (i.e. up to 2 mm).Neste trabalho são propostas técnicas de pós-processamento de fibras óticas com o intuito de produzir sensores de fibra ótica de fácil fabrico, com baixo custo e com características competitivas comparadas com os demais sensores. O primeiro dispositivo baseou-se em interferómetros multimodais. Estes foram feitos através da fusão de fibras óticas multimodo tanto de vidro (GOF) como de polímero (POF) entre duas fibras óticas monomodo de vidro. Para o sensor à base de GOF foi obtida uma sensibilidade de 4.6 pm/bar. Já para o interferómetro multimodal baseado em POF, foi obtida uma sensibilidade de 58 pm/bar, que corresponde a uma melhoria da sensibilidade de doze vezes quando comparada com o sensor baseado em GOF. Além disso, esta é cinco vezes superior à obtida para tecnologia de redes de Bragg em POF. Esta melhoria na sensibilidade torna este sensor muito promissor, uma vez que permite obter resoluções muito maiores. O segundo sensor de fibra ótica abordado neste trabalho consistiu em redes de período longo mecanicamente induzidas. Estas foram obtidas através de metodologias de simples fabricação, que consistiam em distribuir periodicamente resina fotopolimerizável numa GOF-monomodo, seguido de um processo de corrosão química que permitiu modular periodicamente o diâmetro da fibra. Este método de produção é muito mais vantajoso comparado com os seus rivais diretos, uma vez que aplica técnicas de produção baratas e de simples reprodução, não exigindo a utilização de tecnologias de fotolitografia ou de deposição química de vapor. A caraterização desta estrutura a parâmetros externos, tais como: tensão longitudinal, deslocamento e temperatura revelaram capacidades promissoras, uma vez que permitiram não só a sintonização da banda espetral tanto em comprimento de onda como também em potência ótica de acoplamento. Os resultados foram bastante promissores no que concerne às caraterizações do deslocamento, uma vez que se obteve uma gama de medição de 0 - 60 mm, o que é maior que aquelas reportadas na literatura (i.e. até 2 mm).Mestrado em Engenharia Físic

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

Advances in Optofluidics

Optofluidics a niche research field that integrates optics with microfluidics. It started with elegant demonstrations of the passive interaction of light and liquid media such as liquid waveguides and liquid tunable lenses. Recently, the optofluidics continues the advance in liquid-based optical devices/systems. In addition, it has expanded rapidly into many other fields that involve lightwave (or photon) and liquid media. This Special Issue invites review articles (only review articles) that update the latest progress of the optofluidics in various aspects, such as new functional devices, new integrated systems, new fabrication techniques, new applications, etc. It covers, but is not limited to, topics such as micro-optics in liquid media, optofluidic sensors, integrated micro-optical systems, displays, optofluidics-on-fibers, optofluidic manipulation, energy and environmental applciations, and so on