Depth Fields: Extending Light Field Techniques to Time-of-Flight Imaging

A variety of techniques such as light field, structured illumination, and time-of-flight (TOF) are commonly used for depth acquisition in consumer imaging, robotics and many other applications. Unfortunately, each technique suffers from its individual limitations preventing robust depth sensing. In this paper, we explore the strengths and weaknesses of combining light field and time-of-flight imaging, particularly the feasibility of an on-chip implementation as a single hybrid depth sensor. We refer to this combination as depth field imaging. Depth fields combine light field advantages such as synthetic aperture refocusing with TOF imaging advantages such as high depth resolution and coded signal processing to resolve multipath interference. We show applications including synthesizing virtual apertures for TOF imaging, improved depth mapping through partial and scattering occluders, and single frequency TOF phase unwrapping. Utilizing space, angle, and temporal coding, depth fields can improve depth sensing in the wild and generate new insights into the dimensions of light's plenoptic function.Comment: 9 pages, 8 figures, Accepted to 3DV 201

Mesoscale Light-matter Interactions

Mesoscale optical phenomena occur when light interacts with a number of different types of materials, such as biological and chemical systems and fabricated nanostructures. As a framework, mesoscale optics unifies the interpretations of the interaction of light with complex media when the outcome depends significantly upon the scale of the interaction. Most importantly, it guides the process of designing an optical sensing technique by focusing on the nature and amount of information that can be extracted from a measurement. Different aspects of mesoscale optics are addressed in this dissertation which led to the solution of a number of problems in complex media. Dynamical and structural information from complex fluids—such as colloidal suspensions and biological fluids—was obtained by controlling the size of the interaction volume with low coherence interferometry. With this information, material properties such as particle sizes, optical transport coefficients, and viscoelastic characteristics of polymer solutions and blood were determined in natural, realistic conditions that are inaccessible to conventional techniques. The same framework also enabled the development of new, scale-dependent models for several important physical and biological systems. These models were then used to explain the results of some unique measurements. For example, the transport of light in disordered photonic lattices was interpreted as a scale-dependent, diffusive process to explain the anomalous behavior of photon path length distributions through these complex structures. In addition, it was demonstrated how specialized optical measurements and models at the mesoscale enable solutions to fundamental problems in cell biology. Specifically, it was found for the first time that the nature of cell motility changes markedly with the curvature of the substrate that the cells iv move on. This particular work addresses increasingly important questions concerning the nature of cellular responses to external forces and the mechanical properties of their local environment. Besides sensing of properties and modeling behaviors of complex systems, mesoscale optics encompasses the control of material systems as a result of the light-matter interaction. Specific modifications to a material’s structure can occur due to not only an exchange of energy between radiation and a material, but also due to a transfer of momentum. Based on the mechanical action of multiply scattered light on colloidal particles, an optically-controlled active medium that did not require specially tailored particles was demonstrated for the first time. The coupling between the particles and the random electromagnetic field affords new possibilities for controlling mesoscale systems and observing nonequilibrium thermodynamic phenomena

Study of efficient transmission and reception of image-type data using millimeter waves

Evaluation of signal processing and modulation techniques for transmission and reception of image type data via millimeter wave relay satellite

Plasmonic Nanoplatforms for Biochemical Sensing and Medical Applications

Plasmonics, the science of the excitation of surface plasmon polaritons (SPP) at the metal-dielectric interface under intense beam radiation, has been studied for its immense potential for developing numerous nanophotonic devices, optical circuits and lab-on-a-chip devices. The key feature, which makes the plasmonic structures promising is the ability to support strong resonances with different behaviors and tunable localized hotspots, excitable in a wide spectral range. Therefore, the fundamental understanding of light-matter interactions at subwavelength nanostructures and use of this understanding to tailor plasmonic nanostructures with the ability to sustain high-quality tunable resonant modes are essential toward the realization of highly functional devices with a wide range of applications from sensing to switching. We investigated the excitation of various plasmonic resonance modes (i.e. Fano resonances, and toroidal moments) using both optical and terahertz (THz) plasmonic metamolecules. By designing and fabricating various nanostructures, we successfully predicted, demonstrated and analyzed the excitation of plasmonic resonances, numerically and experimentally. A simple comparison between the sensitivity and lineshape quality of various optically driven resonances reveals that nonradiative toroidal moments are exotic plasmonic modes with strong sensitivity to environmental perturbations. Employing toroidal plasmonic metasurfaces, we demonstrated ultrafast plasmonic switches and highly sensitive sensors. Focusing on the biomedical applications of toroidal moments, we developed plasmonic metamaterials for fast and cost-effective infection diagnosis using the THz range of the spectrum. We used the exotic behavior of toroidal moments for the identification of Zika-virus (ZIKV) envelope proteins as the infectious nano-agents through two protocols: 1) direct biding of targeted biomarkers to the plasmonic metasurfaces, and 2) attaching gold nanoparticles to the plasmonic metasurfaces and binding the proteins to the particles to enhance the sensitivity. This led to developing ultrasensitive THz plasmonic metasensors for detection of nanoscale and low-molecular-weight biomarkers at the picomolar range of concentration. In summary, by using high-quality and pronounced toroidal moments as sensitive resonances, we have successfully designed, fabricated and characterized novel plasmonic toroidal metamaterials for the detection of infectious biomarkers using different methods. The proposed approach allowed us to compare and analyze the binding properties, sensitivity, repeatability, and limit of detection of the metasensing device

Recent Progress in Optical Fiber Research

This book presents a comprehensive account of the recent progress in optical fiber research. It consists of four sections with 20 chapters covering the topics of nonlinear and polarisation effects in optical fibers, photonic crystal fibers and new applications for optical fibers. Section 1 reviews nonlinear effects in optical fibers in terms of theoretical analysis, experiments and applications. Section 2 presents polarization mode dispersion, chromatic dispersion and polarization dependent losses in optical fibers, fiber birefringence effects and spun fibers. Section 3 and 4 cover the topics of photonic crystal fibers and a new trend of optical fiber applications. Edited by three scientists with wide knowledge and experience in the field of fiber optics and photonics, the book brings together leading academics and practitioners in a comprehensive and incisive treatment of the subject. This is an essential point of reference for researchers working and teaching in optical fiber technologies, and for industrial users who need to be aware of current developments in optical fiber research areas

High-Speed Wide-Field Time-Correlated Single-Photon Counting Fluorescence Lifetime Imaging Microscopy

Fluorescence microscopy is a powerful imaging technique used in the biological sciences to identify labeled components of a sample with specificity. This is usually accomplished through labeling with fluorescent dyes, isolating these dyes by their spectral signatures with optical filters, and recording the intensity of the fluorescent response. Although these techniques are widely used, fluorescence intensity images can be negatively affected by a variety of factors that impact the fluorescence intensity. Fluorescence lifetime imaging microscopy (FLIM) is an imaging technique that is relatively immune to intensity fluctuations and also provides the unique ability to directly monitor the microenvironment surrounding a fluorophore. Despite the benefits associated with FLIM, the applications to which it is applied are fairly limited due to long image acquisition times and high cost of traditional hardware. Recent advances in complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diodes (SPADs) have enabled the design of low-cost imaging arrays that are capable of recording lifetime images with acquisition times greater than one order of magnitude faster than existing systems. However, these SPAD arrays have yet to realize the full potential of the technology due to limitations in their ability to handle the vast amount of data generated during the commonly used time-correlated single-photon counting (TCSPC) lifetime imaging technique. This thesis presents the design, implementation, characterization, and demonstration of a high speed FLIM imaging system. The components of this design include a CMOS imager chip in a standard 0.13 μm technology containing a custom CMOS SPAD, a 64-by-64 array of these SPADs, pixel control circuitry, independent time-to-digital converters (TDCs), a FLIM specific datapath, and high bandwidth output buffers. In addition to the CMOS imaging array, a complete system was designed and implemented using a printed circuit board (PCB) for capturing data from the imager, creating histograms for the photon arrival data using field-programmable gate arrays, and transferring the data to a computer using a cabled PCIe interface. Finally, software is used to communicate between the imaging system and a computer.The dark count rate of the SPAD was measured to be only 231 Hz at room temperature while maintaining a photon detection probability of up to 30\%. TDCs included on the array have a 62.5 ps resolution and a 64 ns range, which is suitable for measuring the lifetime of most biological fluorophores. Additionally, the on-chip datapath was designed to handle continuous data transfers at rates capable of supporting TCSPC-based lifetime imaging at 100 frames per second. The system level implementation also provides sufficient data throughput for transferring up to 750 frames per second from the imaging system to a computer. The lifetime imaging system was characterized using standard techniques for evaluating SPAD performance and an electrical delay signal for measuring the TDC performance. This thesis concludes with a demonstration of TCSPC-FLIM imaging at 100 frames per second -- the fastest 64-by-64 TCSPC FLIM that has been demonstrated. This system overcomes some of the limitations of existing FLIM systems and has the potential to enable new application domains in dynamic FLIM imaging

Trade-off analysis of modes of data handling for earth resources (ERS), volume 1

Data handling requirements are reviewed for earth observation missions along with likely technology advances. Parametric techniques for synthesizing potential systems are developed. Major tasks include: (1) review of the sensors under development and extensions of or improvements in these sensors; (2) development of mission models for missions spanning land, ocean, and atmosphere observations; (3) summary of data handling requirements including the frequency of coverage, timeliness of dissemination, and geographic relationships between points of collection and points of dissemination; (4) review of data routing to establish ways of getting data from the collection point to the user; (5) on-board data processing; (6) communications link; and (7) ground data processing. A detailed synthesis of three specific missions is included

Microfabrication of photonic devices for mid-infrared optical applications

This thesis details research into the microfabrication of photonic devices for mid-infrared optical applications using the technique of ultrafast laser inscription. A diverse range of devices and materials is explored, including the first fabrication and development of an ultrafast laser inscribed mid-infrared waveguide laser source in thulium-doped sesquioxide ceramic gain media. The source produced 81 mW of output power at 1942 nm with a maximum slope efficiency of 9.5% demonstrating progress towards compact, low-threshold and efficient ultrafast laser written waveguide laser sources near 2 μm with the potential for high pulse repetition rate and ultrashort pulse operation. Also shown is the first demonstration of ultrafast laser inscription enabled selective chemical etching of chalcogenide glass. Investigations into the etching of modified regions in gallium lanthanum sulphide glass showed they could be etched at a rate ~13.3 times greater than the un-modified bulk. This result was explored further as a potential route to the production of optofluidic sensors for gas, liquid chemical or biomedical samples. The first demonstration and characterisation of ultrafast laser written waveguides in the chalcogenide glass GASIR-1 is also described. The waveguides were employed for chip scale supercontinuum generation producing the broadest and deepest Infrared supercontinuum from an ultrafast laser inscribed waveguide to-date, spanning ~4 μm from 2.5 to 6.5 μm, which has applications in remote sensing. Finally, the design, build and commissioning of an advanced laser processing setup suitable for ultrafast laser inscription is also detailed