There is an unprecedented need in neuroscience and medical research for the precise imaging of individual neurons and their interconnectivity in an effort to achieve a more complete understanding of neurological illness and cognitive growth. While several imaging architectures successfully detect active neural tissue, fluorescent imaging through head-mounted microscopes is becoming a standard method of imaging neural circuitry in freely behaving animals. At Boston University, the Gardner Group developed a miniaturized, open-source, single-photon ‘finch-scope’ to spur rapid prototyping in head-mounted miniscope technology. While experimentally convenient, the finch-scope and other miniscope platforms are limited by their native depth of field and may only detect a thin layer of active neurons in a neurological volume. In this Master’s Thesis Project, I will investigate utilizing optical phase masks integrated in the Fourier plane of the finch-scope to invoke a less-diffractive Bessel point spread function. Next, I will experimentally justify the extended depth of field nature of these phase masks by imaging the axial profile of a 10μm fluorescent pinhole object with a modified finch-scope.

Imaging systems have long been designed in separated steps: the experience-driven optical design followed by sophisticated image processing. Such a general-propose approach achieves success in the past but left the question open for specific tasks and the best compromise between optics and post-processing, as well as minimizing costs. Driven from this, a series of works are proposed to bring the imaging system design into end-to-end fashion step by step, from joint optics design, point spread function (PSF) optimization, phase map optimization to a general end-to-end complex lens camera. To demonstrate the joint optics application with image recovery, we applied it to flat lens imaging with a large field of view (LFOV). In applying a super-resolution single-photon avalanche diode (SPAD) camera, the PSF encoded by diffractive op tical element (DOE) is optimized together with the post-processing, which brings the optics design into the end-to-end stage. Expanding to color imaging, optimizing PSF to achieve DOE fails to find the best compromise between different wavelengths. Snapshot HDR imaging is achieved by optimizing a phase map directly. All works are demonstrated with prototypes and experiments in the real world. To further compete for the blueprint of end-to-end camera design and break the limits of a simple wave optics model and a single lens surface. Finally, we propose a general end-to-end complex lens design framework enabled by a differentiable ray tracing image formation model. All works are demonstrated with prototypes and experiments in the real world. Our frameworks offer competitive alternatives for the design of modern imaging systems and several challenging imaging applications.

Over a wide range of applications, optical systems have utilized conventional optics in order to provide the ability to engineer the properties of incident infra-red fields in terms of the transmitted field spectral, spatial, amplitude, phase, and polarization characteristics. These micro/nano-optical elements that provide specific optical functionality can be categorized into subcategories of refractive, diffractive, multi-layer thin film dichroics, 3-D photonic crystals, and polarization gratings. The feasibility of fabrication, functionality, and level of integration which these elements can be used in an optical system differentiate which elements are more compatible with certain systems than others. With enabling technologies emerging allowing for a wider range of options when it comes to lithographic nano/micro-patterning, dielectric growth, and transfer etching capabilities, optical elements that combine functionalities of conventional optical elements can be realized. Within this one class of optical elements, it is possible to design and fabricate components capable of tailoring the spectral, spatial, amplitude, phase, and polarization characteristics of desired fields at different locations within an optical system. Optical transmission filters, polarization converting elements, and spectrally selective reflecting components have been investigated over the course of this dissertation and have been coined  MOSSE,' which is an acronym for micro-optic-spectral-spatial-elements. Each component is developed and fabricated on a wafer scale where the thin film deposition, lithographic exposure, and transfer etching stages are decoupled from each other and performed in a sequential format. This facilitates the ability to spatially vary the optical characteristics of the different MOSSE structures across the surface of the wafer itself.

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In this thesis an investigation into novel beams and optical manipulation is presented. Sculpting the phase profile of a Gaussian beam can result in the generation of a beam with unusual properties. Described in this thesis are optical vortices, Bessel beams and Airy beams. Additionally, optical manipulation was investigated using both novel beams and Gaussian beams with an emphasis on the use of a broad bandwidth laser source. The generation of multiple broadband optical trap sites was explored, and the transfer of orbital angular momentum from a broadband optical vortex to trapped microspheres was demonstrated. An introduction to the thesis and an overview of laser sources used for optical manipulation is presented in Chapters 1 and 2. Chapters 3 and 4 detail the background of optical manipulation and novel beam shaping. In Chapter 5, an investigation into the generation of multiple broadband optical trap sites is presented. Chapter 6 details the use of a ‘white light’ optical vortex to transfer orbital angular momentum to trapped microspheres. Chapter 7 presents the results of an investigation carried out using a supercontinuum source to characterise the wavelength and spatial coherence dependence of the properties of an optical Airy beam. The use of a monochromatic laser to generate Bessel beams that propagate along curved trajectories is detailed in Chapter 8. Chapter 9 summarises the thesis and suggests future work.

This thesis describes investigations into the optical and device design of organic light-emitting diodes (OLEDs) with the aim of exploring the factors controlling the spatial emission pattern of OLEDs and developing novel OLEDs with directional emission by applying wavelength-scale photonic microstructure. The development of directional OLEDs was broken down into two steps: the development of efficient narrow linewidth OLEDs and the integration of wavelength-scale photonic microstructures into narrow linewidth OLEDs. The narrow linewidth OLEDs were developed using europium (Eu) complexes. The electrical optimisation of solution-processed Eu-based OLEDs using commercially available materials was investigated. The optimised Eu-based OLEDs gave an external quantum efficiency of 4.3% at a display brightness of 100 cd/m². To our knowledge, this is the highest efficiency reported for solution-processed Eu-based OLED devices, and the efficiency roll-off has been reduced compared with other reported references. Photonic microstructures were applied to develop directional OLEDs using the efficient Eu-based OLEDs. Two contrasting strategies were used. One was to embed photonic microstructures into Eu-based OLEDs, the other was to couple photonic microstructures externally onto the devices. The microstructured devices developed by the former strategy boosted the emitted power in desired angles in both s- and p-polarisations and doubled the fraction of emission in an angle range of 4⁰. The devices developed by the external coupling strategy achieved even higher directionality and the out-coupled emission was a confined beam with easy control of beam steering. Around 90% of the emitted power was confined in an angular range of 20⁰ in the detection plane. The optical properties can be optimised independently without compromising the electrical properties of devices, which gives major advantages in terms of effectiveness and versatility. Optical models were also developed to investigate the out-coupling mechanism of various trapped modes and develop OLEDs with stronger directionality.

Soft x-ray microscopy in the water-window (λ = 2.28 nm – 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x‑ray facilities, thereby limiting their accessibility for a wider scientific community. This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments are supported by extensive numerical modelling for improved understanding of partially coherent image formation and stray light in soft x-ray microscopes. The models are useful tools for studying effects of zone plate optics or optical design of the microscope on image formation and quantitative accuracy in soft x-ray tomography. / QC 20110221

Orientador: Jose Joaquin Lunazzi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T07:18:00Z (GMT). No. of bitstreams: 1 RodriguezRivera_NoemiInes_D.pdf: 6088514 bytes, checksum: c2c66dc6b71f900d00c6832f96aaf3eb (MD5) Previous issue date: 2007 / Resumo: Apresentamos neste trabalho a análise da formação de imagens por elementos difrativos com luz branca fazendo o traçado de raios pelas direções principais. O primeiro sistema analisado é composto por duas redes de difração e uma fenda, o segundo por dois elementos bidimensionais de estrutura espiral e um orifício, que formam imagens ortoscópicas (relevo natural). A partir das análises mencionadas desenvolvemos um sistema de dois elementos difrativos sem elementos intermediários que forma uma imagem de luz branca que é pancromática, porque oferece as cores originais. Além disso, apresentamos um sistema formador de uma imagem por transmissão que consiste na projeção de objetos usando uma fonte linear (filamento extenso) e um elemento difrativo. Aproveitando as propriedades de uma fonte linear, desenvolvemos um sistema que permite que espelhos ou lentes imperfeitos gerem imagens nítidas. Mediante estes sistemas visamos conseguir um dia a formação de imagens convergentes, entretanto já oferecemos novas maneiras de se exibir imagens tridimensionais atrativas e amplas / Abstract: We present the analysis of the formation of images by diffractive elements using white light by performing ray-tracing through main directions. The first system we describe is composed of two diffraction gratings and a slit, the second by two bi-dimensional spiral elements and a hole aperture, generating ortoscopic (natural relief) images. From this we had found a system of two diffractive elements without any intermediating element that makes and image which is panchromatic because gives original colors. Furthermore, we present a transmission imaging system that projects objects by means of a linear source (extended filament) and a diffractive element. Profiting the imaging properties of that linear source we also developed a system for mirrors and lenses having no sharpness to generate sharp images. By studying these systems we seek to find a way to achieve the making of convergent images and we already offer new ways to exhibit attractive and large three-dimensional images / Doutorado / Física / Doutor em Ciências

This master’s thesis develops a novel method of digital holography, from recent studies known as Fresnel Incoherent Correlation Holography (FINCH). The method enables the reconstruction of the correlation records of three-dimensional objects, captured under quasi-monochromatic, incoherent illumination. The experimental system is based on an action of a Spatial Light Modulator, driven by computer generated holograms to create mutually correlated beams. Both optical and digital parts of the experiment can be carried out using procedures of classical holography, diffractive optics and digital holography. As an important theoretical result of the master’s thesis, a new computational model was proposed, which allows to describe the experiment completely with respect to its two basic phases. The proposed model allows to understood the method intuitively and can be used additionally for analysis and interpretation of the imaging parameters and the system optimalization. The theoretical part of the master’s thesis also presents a detailed description of the correlation imaging based on an appropriate reconstruction process. Computational models were developed for both monochromatic and quasi-monochromatic illumination. In experimental part, all theoretical results were verified. The imaging parameters were examined using standard resolution target tests and appropriate biological samples. As an original experimental result, spiral modification of the system resulting in a vortex imaging was proposed and realized. Here, a selective edge enhancement of three-dimensional objects is possible, resulting in a significant extension of possible applications of the method.

The full complex, spatial modulation of light at high frame rates is essential for a variety of applications. In particular, emerging techniques applied to scattering media, such as Digital Optical Phase Conjugation and Wavefront Shaping, request challenging performance parameters. They refer to imaging tasks inside biological media, whose characteristics concerning the transmission and reflection of scattered light may change over time within milliseconds. Thus, these methods call for frame rates in the kilohertz range. Existing solutions typically offer frame rate capabilities below 100 Hz, since they rely on liquid crystal spatial light modulators (SLMs). We propose a diffractive MEMS optical system for this application range. It relies on an analog, tilt-type micro mirror array (MMA) based on an established SLM technology, where the standard application is grayscale amplitude control. The new MMA system design allows the phase manipulation at high-speed as well. The article studies properties of the appropriate optical setup by simulating the propagation of the light. Relevant test patterns and sensitivity parameters of the system will be analyzed. Our results illustrate the main opportunities of the concept with particular focus on the tilt mirror technology. They indicate a promising path to realize the complex light modulation at frame rates above 1 kHz and resolutions well beyond 10,000 complex pixels.