Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication

Optics and photonics are among the key technologies of the 21st century, and offer potential for novel applications in areas such as sensing and spectroscopy, analytics, monitoring, biomedical imaging/diagnostics, and optical communication technology. The high degree of control over light fields, together with the capabilities of modern processing and integration technology, enables new optical measurement systems with enhanced functionality and sensitivity. They are attractive for a range of applications that were previously inaccessible. This Special Issue aims to provide an overview of some of the most advanced application areas in optics and photonics and indicate the broad potential for the future

Application of Resonant and Non-Resonant Laser-Induced Plasmas for Quantitative Fuel-to-Air Ratio and Gas-Phase Temperature Measurements

In this work, two laser-induced plasma techniques are used for gas-phase chemical and temperature measurements. The first technique, laser-induced breakdown spectroscopy (LIBS) is applied for fuel-to-air ratio (FAR) measurements in a well calibrated Hencken flame. In Chapter I, relevant technical and background information for each technique is provided. In Chapter II, measurements are first performed for high-pressure (1-11 Bar) methane-air flames, for which calibration curves are generated using the emission ratio of hydrogen at 656 nm and ionic nitrogen at 568 nm. The effect of pressure on the sensitivity and precision of the resulting calibrated curves is evaluated. Results indicate a degradation of measurement precision as environmental pressure increases, with data indicating that fluctuations of the plasma play a major part in this behavior. Expanding upon this work with LIBS, a comparison of FAR calibration curve results for atmospheric methane-air Hencken flame using three different laser pulse widths, femto-, pico-, and nanosecond regimes, is done in Chapter III. The results are discussed in the context of potential advantages for high-pressure LIBS-based FAR measurements. Results indicate that while nanosecond duration pulses provide better precision at 1 Bar conditions, femtosecond duration pulses might be better suited for high-pressure measurements.In Chapter IV, the radar REMPI technique, which uses microwave scattering from a plasma created by selective multiphoton ionization of molecular oxygen, is used for gas-phase temperature measurements through the wall of ceramic-enclosed environments. Specifically, measurements are done through the wall of a heated laboratory flow reactor and through the wall of a ceramic well-stirred reactor. Results show good agreement with thermocouple and/or computational modeling and the effectiveness of radar REMPI for through-the-wall measurements.In Chapter V, a new technique is discussed, namely acoustic REMPI, which utilizes the pressure wave generated from the creation of the REMPI plasma for diagnostics. The acoustic emission from the plasma is characterized and used for gas-phase temperature measurements. Comparison, with radar REMPI shows a high-level of agreement.Finally, in Chapter VI, a summary of the work in this dissertation is provided along with a discussion of potential for work in the future

Roadmap on ultrafast optics

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3D Micromachining of Optical Devices on Transparent Material by Ultrafast Laser

Ultrafast lasers, also referred to as ultrashort pulse lasers, have played an important role in the development of next generation manufacturing technologies in recent years. Their broad range of applications has been investigated in the field of microstructure processing for the biomedical, optical, and many other laboratory and industrial fields. Ultrafast laser machining has numerous unique advantages, including high precision, a small heat affected area, high peak intensity, 3D direct-writing, and other flexible capabilities When integrated with optical delivery, motion devices and control systems, one-step fabrication of assemble-free micro-devices can be realized. In particular, ultrafast lasers enable the creation of various three-dimensional, laser-induced modifications using an extremely high peak intensity over a short time frame, producing precise ablation of material and a small heat affected area in transparent materials. In contrast, lasers with longer pulse durations are based on a thermal effect, which results in significant melting in the heat affected area. In general, ultrafast laser micromachining can be used either to subtract material from or to change the material properties of both absorptive and transparent substances. Recently, integrated micro-devices including optical fiber sensors, microfluidic devices, and lab-on-chips (LOC) have gained worldwide recognition because of their unique characteristics. These micro-devices have been widely used for a broad range of applications, from fundamental research to industry. The development of integrated glass micro-devices introduced new possibilities for biomedical, environmental, civil and other industries and research areas. Of these devices, optical fiber sensors are recognized for their small size, accuracy, resistance to corrosion, fast response and high integration. They have demonstrated their excellent performance in sensing temperature, strain, refractive index and many other physical quantities. In addition to the all-in-fiber device, the LOC is another attractive candidate for use in micro-electro-mechanical systems (MEMS) because it includes several laboratory functions on a single integrated circuit. LOCs provide such advantages as low fluid volume consumption, improved analysis and response times due to short diffusion distances, and better process control, all of which are specific to their application. Combining ultrafast laser micromachining techniques with integrated micro-devices has resulted in research on a variety of fabrication methods targeted for particular purposes. In this dissertation, the direct creation of three-dimensional (3D) structures using an ultra-fast laser was investigated for use in optical devices. This research was motivated by the desire to understand more fully the relationship among laser parameters, material properties and 3D optical structures. Various all-in-fiber sensors in conjunction with femtosecond laser ablation and irradiation were investigated based on magnetic field, temperature and strain application. An incoherent optical carrier based microwave interferometry technique was used for in-situ weak reflector fabrication and a picosecond laser micromachining technique was introduced for developing LOCs with unlimited utilization potential

Impulse radio ultra wideband over fiber techniques for broadband in-building network applications

In recent years, the demand for high bandwidth and mobility from the end users has been continuously growing. To satisfy this demand, broadband communication technologies that combined the benefit of both wired and wireless are considered as vital solutions. These hybrid optical wireless solutions enable multi-Gbit/s transmission as well as adequate flexibility in terms of mobility. Optical fiber is the ideal medium for such hybrid solution due its signal transparency and wide bandwidth. On the other hand, ultra wideband(UWB) radio over optical fiber technology is considered to be one of the key promising technologies for broadband communication and sensor network applications. The growing interest for UWB is mainly due to its numerous attractive features, such as low power spectral density, tolerance to multipath fading, low probability of interception, coexistence with other wireless services and capability of providing cost-effective > 1 Gb/s transmission. The main idea of UWB over fiber is to deliver UWB radio signals over optical channels, where the optical part serves as a backbone communication infrastructure to carry the UWB signal with a bandwidth of several GHz. This enables multiple novel applications such as: range extension of high speed wireless personal area networks (WPANs), low cost distributed antenna systems, secure and intelligent networks, or delivering broadband services to remote areas. In particular, this thesis deals with novel concepts on shaping and generation of IR-UWB pulses, theoretical and experimental demonstrations over different fiber types, routing of integrated wired/wireless IR-UWB services and effect of fiber types on ranging/localization of IR-UWB-over-fiber systems. Accordingly, this thesis investigates techniques for delivery of high data rate wireless services using impulse radio ultra wideband (IR-UWB) over fiber technology for both access and in-building network applications. To effectively utilize the emission mask imposed for UWB technologies by the Federal Communications Commission(FCC), novel pulse shaping techniques have been investigated and experimentally demonstrated. Comparison of the proposed pulses with conventional ones in terms of the compliance to the FCC-mask requirements, spectral power efficiencies and wireless coverage has been theoretically studied. Simple and efficient optical generation of the new pulse has been experimentally demonstrated. Furthermore, performance evaluation of 2 Gb/s transmission of IR-UWB over different types of fiber such as 25 km silica single-mode, 4.4 km silica multi-mode and 100 m plastic heavily-multi-mode fiber have been performed. To improve the functionalities of in-building networks for the delivery of wireless services; techniques that provide flexibility in terms of dynamic capacity allocation have been investigated. By employing wavelength conversion based on cross-gain modulation in optical semiconductor amplifiers(SOA), routing of three optical channels of IR-UWB over fiber system has been experimentally realized. To reduce the cost of the overall system and share the optical infrastructure, an integrated testbed for wired baseband data and wireless IR-UWB over 1 km SMF-28 fiber has been developed. Accordingly, 1.25 Gb/s wired baseband and 2 Gb/s wireless IR-UWB data have been successfully transmitted over the testbed. Furthermore, to improve the network flexibility, routing of both wired baseband and wireless signals has been demonstrated. Additionally, the ranging and localization capability of IR-UWB over fiber for in-door wireless picocells have been investigated. The effect of different fiber types (4 km SMF, 4.4 km GI-MMF and 100 m PF GI-POF) on the accuracy of the range estimation using time-of-arrival (ToA) ranging technique has been studied. A high accuracy in terms of cm level was achieved due to the combined effect of high bandwidth IR-UWB pulses, short reach fiber and low chromatic dispersion at 1300nm wavelength. Furthermore, ranging/ localization using IR-UWB over fiber system provides additional benefit of centralizing complex processing algorithms, simplifying radio access points, relaxing synchronization requirement, enabling energy-efficient and efficient traffic management networks. All the concepts, design and system experiments presented in this thesis underline the strong potential of IR-UWB for over optical fiber(silica and plastic) techniques for future smart, capacity and energy-efficient broadband in-building network applications

A trillion frames per second: the techniques and applications of light-in-flight photography

Cameras capable of capturing videos at a trillion frames per second allow to freeze light in motion, a very counterintuitive capability when related to our everyday experience in which light appears to travel instantaneously. By combining this capability with computational imaging techniques, new imaging opportunities emerge such as three dimensional imaging of scenes that are hidden behind a corner, the study of relativistic distortion effects, imaging through diffusive media and imaging of ultrafast optical processes such as laser ablation, supercontinuum and plasma generation. We provide an overview of the main techniques that have been developed for ultra-high speed photography with a particular focus on `light-in-flight' imaging, i.e. applications where the key element is the imaging of light itself at frame rates that allow to freeze it's motion and therefore extract information that would otherwise be blurred out and lost.Comment: Published in Reports on progress in Physic

Fiber Bragg Grating Based Sensors and Systems

This book is a collection of papers that originated as a Special Issue, focused on some recent advances related to fiber Bragg grating-based sensors and systems. Conventionally, this book can be divided into three parts: intelligent systems, new types of sensors, and original interrogators. The intelligent systems presented include evaluation of strain transition properties between cast-in FBGs and cast aluminum during uniaxial straining, multi-point strain measurements on a containment vessel, damage detection methods based on long-gauge FBG for highway bridges, evaluation of a coupled sequential approach for rotorcraft landing simulation, wearable hand modules and real-time tracking algorithms for measuring finger joint angles of different hand sizes, and glaze icing detection of 110 kV composite insulators. New types of sensors are reflected in multi-addressed fiber Bragg structures for microwave–photonic sensor systems, its applications in load-sensing wheel hub bearings, and more complex influence in problems of generation of vortex optical beams based on chiral fiber-optic periodic structures. Original interrogators include research in optical designs with curved detectors for FBG interrogation monitors; demonstration of a filterless, multi-point, and temperature-independent FBG dynamical demodulator using pulse-width modulation; and dual wavelength differential detection of FBG sensors with a pulsed DFB laser