Thesis (M.S.)--Oregon Graduate Center, 1976.

Thesis (M.S.)--Oregon Graduate Center, 1979.

M.S. / Applied Physics / This monograph summarizes the theory and construction of a tunable continuous wave (CW) Rhodamine 6G dye laser longitudinally pumped by an argon laser. (from Introduction; no abstract available)

I investigate the use of vertical cavity surface emitting lasers (VCSELs) for portable optical neural imaging. In particular, I attempt to use one laser source to produce the different illumination needed for three techniques, imaging flow, oxygenation, and fluorescence. Our group's goal is to combine these techniques using a single source in a simple imaging format, which can be modified for portable use in awake animals. We exploit tuning properties of VCSELs to implement two distinct operation schemes with different illumination characteristics. Single mode operation provides high speckle contrasts, used to map flow speeds in laser speckle contrast imaging (LSCI). Sweep operation provides low noise, allowing us to image small signal changes with intrinsic optical signal imaging (IOSI), which relate to blood oxygenation. Finally, we use our VCSEL devices for on-chip integrated fluorescence sensing. Future work aims to develop a fully portable format, using CMOS detectors and integrated circuit control.

I investigate the use of vertical cavity surface emitting lasers (VCSELs) for portable optical neural imaging. In particular, I attempt to use one laser source to produce the different illumination needed for three techniques, imaging flow, oxygenation, and fluorescence. Our group's goal is to combine these techniques using a single source in a simple imaging format, which can be modified for portable use in awake animals. We exploit tuning properties of VCSELs to implement two distinct operation schemes with different illumination characteristics. Single mode operation provides high speckle contrasts, used to map flow speeds in laser speckle contrast imaging (LSCI). Sweep operation provides low noise, allowing us to image small signal changes with intrinsic optical signal imaging (IOSI), which relate to blood oxygenation. Finally, we use our VCSEL devices for on-chip integrated fluorescence sensing. Future work aims to develop a fully portable format, using CMOS detectors and integrated circuit control.

The resonant interaction of light with metal nanoparticles can result in extraordinary optical effects in both the near and far fields. Plasmonics, the study of this interaction, has the potential to enhance performance in a wide range of applications, including sensing, photovoltaics, photocatalysis, biomedical imaging, diagnostics, and treatment. However, the mechanisms of plasmonic enhancement often remain poorly understood, limiting the design and effectiveness of plasmonics for advanced applications. This dissertation focuses on evaluating the mechanisms of plasmonic enhancement and distinguishing between near and far field effects using simulations and experimental results. Thorough characterization of metal nanoparticle colloids shows that electromagnetic simulations can be used to accurately predict the optical response of nanoparticles only if the true shapes and size distributions are taken into account. By coupling these optical interaction calculations with heat transfer models, experimental limits for the maximum optical power before nanoparticle melting can be found. These limits are important for plasmonic multiphoton luminescence imaging applications. Subsequently, we demonstrate ultrafast laser plasmonic nanoablation of silicon substrates using gold nanorods to identify the near-field enhancement and mechanism of plasmon-assisted ablation. The experimentally observed shape of the ablation region and reduction of the ablation threshold are compared with simulations to show the importance of the enhanced electromagnetic fields in near-field nanoablation with plasmonic nanoparticles. The targeted use of plasmonic nanoparticles requires narrow size distribution colloids, because wide size distributions result in a blurring and weakening of the optical response. A new synthesis method is presented for the seeded-growth of nearly monodisperse metal nanoparticles ranging from 10 to 100 nm in diameter, both with and without dielectric shells of controlled thickness. This method is used to acquire fine control over the position and width of the plasmonic peak response. We also demonstrate self-assembled sub-monolayers of these particles with controllable concentrations, which is ideal for looking at plasmonic effects in surface and layered geometries. Finally, we present results for the spatial distribution of absorption around plasmonic nanoparticles. We introduce field-based definitions for distinguishing near-field and far-field regions and develop a new set of equations to determine the point-by-point enhanced absorption in a medium around a plasmonic nanoparticle. This set of equations is used to study plasmon-enhanced optical absorption for thin-film photovoltaic cells. Plasmonic nanoparticle systems are identified using simulations and proof-of-concept experiments are used to demonstrate the potential of this approach.

Graduation date: 1991

We present the fabrication of InGaAsP/InP buried heterostructure spot-size converter lasers. In the lateral conversion, we use photolithography to make tapered ridge waveguides. In the vertical conversion, we use a pair of step-index passive waveguides, namely guard waveguides (GWs), in the two sides of the step-index active waveguide region to increase optical-field profile. In order to decrease leakage current, we use a p-n-p current blocking structure by MOCVD regrowth. From numerical simulations, the far-field divergence is 21x21. The step-index GW structure shows an internal efficiency of 63%. However, the BH lasers did not lase from our fabrication processes. From the I-V characteristics, a large leakage current has bypassed through the blocking structure. The reason may relate to the high background doping concentration of our MOCVD growth.

Rapport de recherche bibliographique DESS : Réseaux d'information et document électronique : Villeurbanne, ENSSIB : 2002.

Thèse de doctorat : Physique : Optoélectronique : Metz : 2008. Thèse de doctorat : Physique : Optoélectronique : Vrije Universiteit Brussel : 2008. / Thèse soutenue en co-tutelle sur ensemble de travaux. Bibliogr.p.239-256. Liste des publications p. 257-260.