Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"gradient index"”.
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New Vistas in Solar Concentration with Gradient Index Optics
… a) the derivation of fundamentally new gradient-index (GRIN) distributions for perfect optical instruments. For the first time, GRIN lenses for visible and solar radiation with refractive index distributions that are amenable to current fabrication techniques are presented. Those lenses …
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Realization of a 3D gradient index medium in porous silicon
… porosification, the material’s refractive index is defined by modulating the current density along the etch direction to change the porosity in either periodic or continuous fashion, making PSi an excellent materials platform for a variety of photonic and gradient refractive index (GRIN) …
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Gradient-Index (GRIN) lenses by Slurry-based Three-Dimensional Printing (S-3DP)
GRIN lenses with vertical index variation and radial index variation have been successfully fabricated using S-3DPTM. Two silica-based material systems, A1203-SiO₂ and BaO-SiO₂, have been studied and used for the fabrication of GRIN lenses. Aluminum nitrate was dissolved in water to provide the …
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Design and manufacturing of all-dielectric optical metamaterial with gradient index of refraction
Gradient index (GRIN) materials offer the most general manipulation over wave fields of light compared to conventional refractive optics, where the light is deflected by the curved surface. The creative way to implementing GRIN optics is to construct a subwavelength structure with the …
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Superior to one of Glass: Natural Gradient index Lenses via Patchy Particle Self-Assembly
… eye in the ocean, a graded refractive index spherical lens is required to maximize the photon flux on the retina, while leaving an eye structure that fits in the head of an animal. This biological lens must also maintain low protein density fluctuation at the length-scale of a …
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Subsurface two-photon lithography: improvements and applications
… performing subsurface controllable refractive index via beam exposure (SCRIBE), two-photon lithography is implemented with a porous material as the writing medium, allowing different densities of photoresist to be created within. Thus, with SCRIBE, a variety of gradient index (GRIN) optical …
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Metamaterial Enhanced Wireless Power Transmission System
… dominate role in improving system performance. A gradient index (GRIN) MTM lens was designed using Ansoft’s High Frequency Structure Simulator (HFSS) to improve antenna gain and thereby increase WPT system performance. A simple WPT demonstration system using microstrip patch antennas (MPAs) …
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Design of a photonic crystal planar Luneburg lens for optical beam steering
… fabricated using CMOS-compatible techniques. The gradient index of the lens is achieved using a photonic crystal consisting of amorphous silicon patterned with a triangular lattice of holes layered on top of silicon nitride. Multiple waveguides can be placed along the focal circle of the lens and …
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Design and transformation of three dimensional pupils : diffractive and subwavelength
… Inhomogeneity is discussed in the context of gradient--index media. The additional thin--film wave guidance effect along the third dimension due to fabrication constraints is investigated in detail with the proposal of an all--analytical solution.
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Large-scale imaging of endothelial calcium from inside intact atreries
… side-viewing imaging probe (consisting of a gradient-index relay lens and an aluminium-coated micro-optical prism), and permits direct visualisation of an area of the endothelium encompassing ~200 cells with subcellular resolution. The system allows arteries to be pressurised within a normal …
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Nano Cost Nano Patterned Template for Surface Enhanced Raman Scattering (SERS) for IN-VITRO and IN-VIVO Applications
… Raman signal, and a probe / a needle with a gradient-index (GRIN) lens in an articulated arm system. In this work, the aluminum metal was employed as not only a base substrate for a sputtered Au nanostructure (conventional view) but also a sacrificial layer for the Au nanostructure on a …
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A parallel branch-and-bound algorithm for thin-film optical systems, with application to realizing a broadband omnidirectional antireflection coating for silicon solar cells
… using multilayer systems, it is shown that a gradient index constraint on the solution can be exploited to significantly reduce the search space and thereby make the algorithm more practical. This optimization system is then used to design a broadband omnidirectional antireflection coating for …
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Epidemiology and molecular characterization of human and canine hookworm
… WB value >0.4. The second was based on a ‘gradient index’ of the product of monthly accumulated GDD and WB values. It was determined that both environmental temperature and moisture are important in the distribution of hookworm. This study supports the validity of the GDD-WB concept for …
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Design and Experimental Applications of Acoustic Metamaterials
… use this metamaterial to realize a 2D broadband gradient index acoustic lens in air. Furthermore, we optimize the lens design by improving each unit cell's performance and we also realize a 2D acoustic ground cloak in air. In addition, we explore the performance of some novel applications (a 2D …
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Multiphoton Endoscopy
… resonant/nonresonant fiber raster scanner and a gradient index lens assembly that are packaged into a 3-mm outer diameter, 4-cm rigid length tube. Our MPE acquires 110 [MICRO SIGN]m x 110 [MICRO SIGN]m multiphoton images with high scan uniformity at 4 frames/s (512 x 512 pixels), and achieves …
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Advances in non-planar electromagnetic prototyping
… permittivity, permeability, and refractive index. While analytical and numerical tools are equipped to analyze the complex configurations of materials and geometry that constitute many proposed devices, realizations have been limited in part due to fabrication. The fabrication processes used …
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Nanomanufacturing of functional nanostructured surfaces for efficient light transport
… enhanced light extraction from high refractive index materials due to their potential to modulate optical behavior on their surfaces. This thesis focuses on design, analysis, and fabrication of functional nanostructured surfaces for efficient light transport, seeking optimized optical …
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Design and Analysis of Quasioptical Components for use in Terahertz Optics and Future CMB Missions
… mission call and a PLA (Polylatic Acid) GRIN (Gradient Index) lens was analysed using GBM (Gaussian Beam Mode) theory and PO (Physical Optics). This thesis also includes the work the author did as part of an international team of 16 students to design a candidate ESA mission. The final chapter, …
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Development of Multi-modal Optical Coherence Tomography Imaging Systems and Probes
… a 6 mm diameter micro stepper motor and a custom Gradient Index (GRIN) achieving 26 μm lateral resolution and real-time imaging with a frame rate of 100 fps. The forward-viewing probes are built using a piezoelectric (PTZ) cantilever scanner and a micro lens, enabling a 4 mm diameter probe size …
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Diffraction-based Optical Architectures for Processing One-dimensional Data
… new methods for designing aberration-free gradient index lenses. Parameter sweeps are demonstrated to find lenses within the framework, with minimal dynamic range of refractive index distributions found from two families of aberration-free collimation lenses. As such, the theoretical tools …
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