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 88 for “"DBR"”.
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Adaptation of VT-Dbr Lasers for LIDAR
<p>Vernier Tuned Distributed Bragg Reflector (VT-DBR) lasers have had great success in the field of Swept-Source Optical Coherence Tomography (SS-OCT) due to their continuous and nearly 40 nm wavelength tuning range in a single longitudinal mode. Fast sweeps allow for real time imaging with …
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Automated SG-DBR Tunable Laser Calibration Optimized for Optical Coherence Tomography Applications
<p>SG-DBR lasers look to solve many problems associated with present OCT sources by being cost effective, smaller in size, more robust, and by operating at faster repetition rates. Swept Source Optical Coherence Tomography (SS-OCT) requires a tunable laser source that exhibits linear frequency …
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Point-Spread Function Assessment of SG-DBR Based Swept Source for OCT Imaging
… Sampled grating distributed Bragg reflector (SG-DBR) lasers are proven in telecom applications and are expected to fulfill the requirements for SS-OCT at a significantly lower cost than alternative solutions.</p> <p>Constructed entirely on a semiconductor substrate, SG-DBR lasers require four …
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Microwave Signal Generation Using Self-Heterodyning of a Fast Wavelength Switching SG-DBR Laser
… using a single-chip fast wavelength-tunable SG-DBR laser. Microwave signals are established by a delayed self-heterodyne technique. The optical frequency of the laser is square-wave modulated between two closely spaced wavelengths. These two wavelengths are made time coincident using a fiber …
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Using Gamification to enhance student engagement at a South African Private Higher Education Institution: A DBR approach
… (PHEI). Utilizing a Design-Based Research (DBR) framework, the research aims to develop evidence-based design principles for effectively incorporating gamification into teaching practices in higher education. The central research question focused on identifying effective design principles …
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The use of satellite remote sensing to determine land water runoff
… the atmosphere and the Divergence Bowen Ratio (DBR). The DBR is the ratio of the horizontal flux of internal and potential energy to the horizontal flux of latent heat in the atmosphere. A tropical DBR of -2 was determined from two independent techniques, from a least squares regression relating …
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Examining A Brief Behavior Progress Monitoring Tool's Sensitivity to Change
… FastBridge - Direct Behavior Rating (FastBridge-DBR), a brief, novel progress monitoring measure, designed to assess student behavioral change in response to a classroom behavioral intervention. Twenty-four elementary teacher-student dyads implemented a daily progress report intervention to …
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Swept-Frequency Sampled Grating Distributed Bragg Reflector Lasers Optimized for Optical Coherence Tomography Applications
… sampled grating distributed Bragg reflector (SG-DBR) laser provides wide wavelength tuning range while exhibiting a wavelength switching speed that is among the fastest currently available. The SG-DBR laser is used to generate linear frequency ramps with high repetition rates. Since the SG-DBR …
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Fabrication and measurements of surface-etched grating distributed Bragg reflector laser
… broad, so a distributed Bragg reflector (DBR) laser is used to make a narrow linewidth laser. The thesis discusses semiconductor lasers that use surface-etched DBR along with the physics of both the semiconductor and the DBR laser. The topics addressed are the fabrication of the broad area …
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Design and Characterization of Integrated Photonic Devices Fabricated Using Selective-Area Epitaxy and Distributed Bragg Reflector Surface Gratings
… devices using distributed Bragg reflectors (DBRs). In this dissertation, ridge-waveguide DBR lasers with first-order surface gratings are investigated. These lasers exhibit low thresholds (6 mA), high slope efficiencies (0.46 W/A), and single-frequency operation with narrow linewidths ($<$25 …
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Neuartige nanostrukturierte Halbleiterlaser und Mikroringresonatoren auf InP-Basis für Wellenlängenmultiplexsysteme in der optischen Nachrichtenübertragung
… 5 beschäftigt sich mit monomodige DFB- oder DBR-Lasern für Wellenlängenmultiplexsysteme im Wellenlängenbereich um 1.55 µm, als Einzelkomponenten oder in Arrays, die eine exakt einstellbarere Wellenlänge und hoher Modenstabilität aufweisen. Durch die Verwendung des DBR-Prinzips kann eine …
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Technological assessment of light-trapping technology for thin-film Si solar cell
… technology of Distributed Bragg Reflector (DBR) with Diffraction Grating (DG) and Anti-Reflection Coating (ARC) for thin film Si solar cell was analyzed from the technology, market, and implementation perspectives. Two applications were investigated. For monocrystalline thin film Si solar …
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Towards a pedagogical framework for construction of historicity: a case of using Wikis among pre-service teachers at Makerere University
… A Design Based Research Methodology (DBR), with theoretically informed solutions aligned to the study problem, was used among pre-service teachers enrolled at Makerere University, Uganda, for the period 2013-2016. Consequently, four phases of DBR were employed: identification of the …
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High efficiency thin film silicon solar cells with novel light trapping : principle, design and processing
… crystal as a distributed Bragg reflector (DBR) and reflection grating. The DBR achieves near unity reflectivity in a wide omnidirectional bandgap completely covering the wavelengths needing light trapping, and the grating can diffract light into large oblique angles and form total internal …
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Compact Femtosecond Lasers for Multiphoton Imaging
… recently introduced Distributed Bragg Reflector (DBR) free technology helps to address these challenges. The second part of this thesis describes the development of 1µm DBR free VECSEL - Membrane External Cavity Surface Emitting Laser (MECSEL), that demonstrated the record CW output power for …
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Wide stripe single and dual wavelength mode semiconductor diode lasers
… internal grating, a distributed Bragg reflector (DBR) grating that was monolithically inserted into the gain section of a semiconductor laser. The result is a single wavelength mode semiconductor laser capable of delivering high power levels. These lasers were made to have an emission wavelength …
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Surface -Etched Distributed Bragg Reflector Lasers in Photonic Integrated Circuits
A high-power DBR laser array is also presented for use in spectral beam combining systems. The laser structure for this application is engineered for high-power applications. The engineering of the lateral optical guiding structure as well as the surface-etched grating is discussed.
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Herstellung und Charakterisierung von kanten- und vertikalemittierenden (Ga)InAs/Ga(In)As-Quantenpunkt(laser)strukturen
… Spiegelschichten aus AlAs und GaAs im unteren DBR (DBR: Distributed Bragg Reflector), einer lambda-dicken Kavität aus GaAs mit einer Quantenpunktschicht im Zentrum und einem oberen DBR mit 20 Perioden. Es konnten Resonatoren mit sehr hohen Güten über 8000 realisiert werden. Für die weiteren …
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Thin-film silicon solar cells : photonic design, process and fundamentals
… grating layer and a distributed Bragg reflector (DBR) for effcient light scattering and reflection, increasing light path length in the thin-film cell. We have understood the operation principles for this design by using photonic band theories and electromagnetic wave simulations. we discover that …
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Expanding Dialogic Space in Online Undergraduate Research Training: A Design-Based Approach
… a dialogic form of Design-Based Research (DBR) to explore the operationalization of expanding online dialogic spaces through the development, implementation, evaluation, and refinement of educational interventions. The DBR combines quantitative methods (content analysis with Epistemic …
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