Matching Items (8)

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Measuring the Index of Refraction of a Medium through the use of a Michelson Interferometer

Description

In this experiment, an attempt was made to measure the index of refraction of a thin glass microscope slide, with a known thickness of 1.01 mm. A monochromatic laser with

In this experiment, an attempt was made to measure the index of refraction of a thin glass microscope slide, with a known thickness of 1.01 mm. A monochromatic laser with wavelength of 532nm was employed to generate the interference pattern through the use of a Michelson interferometer. The slide was placed in the path of one of the beams. The slide could then be rotated through a series of angles, and, from the resulting changes in the interference pattern, the index of refraction of the slide could be extracted. The index of refraction was found to be 1.5±0.02.

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Agent

Created

Date Created
  • 2014-05

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Characterization of Zika Virus Inactivated by Ultrashort Pulsed Laser as a Source for Vaccine Development

Description

The objective of this thesis was to determine whether Zika Virus (ZIKV) can be effectively inactivated by Selective Photonic Disinfection (SEPHODIS) and determine whether key proteins involved in the infection

The objective of this thesis was to determine whether Zika Virus (ZIKV) can be effectively inactivated by Selective Photonic Disinfection (SEPHODIS) and determine whether key proteins involved in the infection process are preserved, making SEPHODIS a possible source for vaccine development. As of January 2018, there have been 3,720 confirmed cases of Congenital Zika Syndrome in infants, making a Zika Vaccine a high priority (Mitchell, 2018). SEPHODIS is a process that involves prolonged exposure of an object to a pulsing laser which can render it ineffective. Initially, ZIKV was subjected to laser inactivation for 6 hours, then a plaque assay was performed on both laser-treated and control samples. ZIKV was inactivated two-fold? after laser treatment, when compared with control, as indicated by the plaque assay results. Additionally, both samples were submitted to ELISA to evaluate antigenicity with a panel of monoclonal and human sera. As a second control, virus inactivated by formaldehyde (2%) was used. ELISA results showed that antigenicity of some proteins were preserved while others were probably disturbed. However, ELISA results show that ZIKV envelope protein (E-protein), the protein responsible for viral entry into cells, was effectively preserved after laser-treatment, implying that if laser parameters were tweaked to obtain more complete inactivation, then SEPHODIS may be an appropriate source for the development of a vaccine.

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Agent

Created

Date Created
  • 2018-05

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Growth and characterization of multisegment chalcogenide alloy nanostructures for photonic applications in a wide spectral range

Description

In this dissertation, I described my research on the growth and characterization of various nanostructures, such as nanowires, nanobelts and nanosheets, of different semiconductors in a Chemical Vapor Deposition (CVD)

In this dissertation, I described my research on the growth and characterization of various nanostructures, such as nanowires, nanobelts and nanosheets, of different semiconductors in a Chemical Vapor Deposition (CVD) system.

In the first part of my research, I selected chalcogenides (such as CdS and CdSe) for a comprehensive study in growing two-segment axial nanowires and radial nanobelts/sheets using the ternary CdSxSe1-x alloys. I demonstrated simultaneous red (from CdSe-rich) and green (from CdS-rich) light emission from a single monolithic heterostructure with a maximum wavelength separation of 160 nm. I also demonstrated the first simultaneous two-color lasing from a single nanosheet heterostructure with a wavelength separation of 91 nm under sufficiently strong pumping power.

In the second part, I considered several combinations of source materials with different growth methods in order to extend the spectral coverage of previously demonstrated structures towards shorter wavelengths to achieve full-color emissions. I achieved this with the growth of multisegment heterostructure nanosheets (MSHNs), using ZnS and CdSe chalcogenides, via our novel growth method. By utilizing this method, I demonstrated the first growth of ZnCdSSe MSHNs with an overall lattice mismatch of 6.6%, emitting red, green and blue light simultaneously, in a single furnace run using a simple CVD system. The key to this growth method is the dual ion exchange process which converts nanosheets rich in CdSe to nanosheets rich in ZnS, demonstrated for the first time in this work. Tri-chromatic white light emission with different correlated color temperature values was achieved under different growth conditions. We demonstrated multicolor (191 nm total wavelength separation) laser from a single monolithic semiconductor nanostructure for the first time. Due to the difficulties associated with growing semiconductor materials of differing composition on a given substrate using traditional planar epitaxial technology, our nanostructures and growth method are very promising for various device applications, including but not limited to: illumination, multicolor displays, photodetectors, spectrometers and monolithic multicolor lasers.

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Agent

Created

Date Created
  • 2015

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Investigation of light absorption and emission in Ge and GeSn films grown on Si substrates

Description

Ge1-ySny alloys represent a new class of photonic materials for integrated optoelectronics on Si. In this work, the electrical and optical properties of Ge1-ySny alloy films grown on Si, with

Ge1-ySny alloys represent a new class of photonic materials for integrated optoelectronics on Si. In this work, the electrical and optical properties of Ge1-ySny alloy films grown on Si, with concentrations in the range 0 ≤ y ≤ 0.04, are studied via a variety of methods. The first microelectronic devices from GeSn films were fabricated using newly developed CMOS-compatible protocols, and the devices were characterized with respect to their electrical properties and optical response. The detectors were found to have a detection range that extends into the near-IR, and the detection edge is found to shift to longer wavelengths with increasing Sn content, mainly due to the compositional dependence of the direct band gap E0. With only 2 % Sn, all of the telecommunication bands are covered by a single detector. Room temperature photoluminescence was observed from GeSn films with Sn content up to 4 %. The peak wavelength of the emission was found to shift to lower energies with increasing Sn content, corresponding to the decrease in the direct band gap E0 of the material. An additional peak in the spectrum was assigned to the indirect band gap. The separation between the direct and indirect peaks was found to decrease with increasing Sn concentration, as expected. Electroluminescence was also observed from Ge/Si and Ge0.98Sn0.02 photodiodes under forward bias, and the luminescence spectra were found to match well with the observed photoluminescence spectra. A theoretical expression was developed for the luminescence due to the direct band gap and fit to the data.

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Agent

Created

Date Created
  • 2011

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Surface plasmon-polariton enhanced lasing: numerical studies

Description

The study of subwavelength behavior of light and nanoscale lasing has broad

potential applications in various forms of computation i.e. optical and quantum, as well as

in energy engineering. Although

The study of subwavelength behavior of light and nanoscale lasing has broad

potential applications in various forms of computation i.e. optical and quantum, as well as

in energy engineering. Although this field has been under active research, there has been

little work done on describing the behaviors of threshold and saturation. Particularly, how

the gain-molecule behavior affects the lasing behavior has yet to be investigated.

In this work, the interaction of surface-plasmon-polaritons (SPPs) and molecules is

observed in lasing. Various phenomenologies are observed related to the appearance of the

threshold and saturation regions. The lasing profile, as a visual delimiter of lasing threshold

and saturation, is introduced and used to study various parametrical dependencies of lasing,

including the number-density of molecules, the molecular thickness and the frequency

detuning between the molecular transition frequency and the SPP resonant frequency. The

molecular population distributions are studied in terminal and dynamical methods and are

found to contain unexpected and theoretically challenging properties. Using an average

dynamical analysis, the simulated spontaneous emission cascade can be clearly seen.

Finally, theoretical derivations of simple 1D strands of dipoles are presented in both

the exact and mean-field approximation, within the density matrix formalism. Some

preliminary findings are presented, detailing the observed behaviors of some simple

systems.

Contributors

Agent

Created

Date Created
  • 2017

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Optical characterization and lasing study of nanowires

Description

Nanowires are one-dimensional (1D) structures with diameter on the nanometer scales with a high length-to-diameter aspect ratio. Nanowires of various materials including semiconductors, dielectrics and metals have been intensively researched

Nanowires are one-dimensional (1D) structures with diameter on the nanometer scales with a high length-to-diameter aspect ratio. Nanowires of various materials including semiconductors, dielectrics and metals have been intensively researched in the past two decades for applications to electrical and optical devices. Typically, nanowires are synthesized using the vapor-liquid-solid (VLS) approach, which allows defect-free 1D growth despite the lattice mismatch between nanowires and substrates. Lattice mismatch issue is a serious problem in high-quality thin film growth of many semiconductors and non-semiconductors. Therefore, nanowires provide promising platforms for the applications requiring high crystal quality materials.

With the 1D geometry, nanowires are natural optical waveguides for light guiding and propagation. By introducing feedback mechanisms to nanowire waveguides, such as the cleaved end facets, the nanowires can work as ultra-small size lasers. Since the first demonstration of the room-temperature ultraviolet nanowire lasers in 2001, the nanowire lasers covering from ultraviolet to mid infrared wavelength ranges have been intensively studied. This dissertation focuses on the optical characterization and laser fabrication of two nanowire materials: erbium chloride silicate nanowires and composition-graded CdSSe semiconductor alloy nanowires.

Chapter 1 – 5 of this dissertation presents a comprehensive characterization of a newly developed erbium compound material, erbium chloride silicate (ECS) in a nanowire form. Extensive experiments demonstrated the high crystal quality and excellent optical properties of ECS nanowires. Optical gain higher than 30 dB/cm at 1.53 μm wavelength is demonstrated on single ECS nanowires, which is higher than the gain of any reported erbium materials. An ultra-high Q photonic crystal micro-cavity is designed on a single ECS nanowire towards the ultra-compact lasers at communication wavelengths. Such ECS nanowire lasers show the potential applications of on-chip photonics integration.

Chapter 6 – 7 presents the design and demonstration of dynamical color-controllable lasers on a single CdSSe alloy nanowire. Through the defect-free VLS growth, engineering of the alloy composition in a single nanowire is achieved. The alloy composition of CdSxSe1-x uniformly varies along the nanowire axis from x=1 to x=0, giving the opportunity of multi-color lasing in a monolithic structure. By looping the wide-bandgap end of the alloy nanowire through nanoscale manipulation, the simultaneous two-color lasing at green and red colors are demonstrated. The 107 nm wavelength separation of the two lasing colors is much larger than the gain bandwidth of typical semiconductors. Since the two-color lasing shares the output port, the color of the total lasing output can be controlled dynamically between the two fundamental colors by changing the relative output power of two lasing colors. Such multi-color lasing and continuous color tuning in a wide spectral range would eventually enable color-by-design lasers to be used for lighting, display and many other applications.

Contributors

Agent

Created

Date Created
  • 2015

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Fabrication and characterization of metallic cavity nanolasers

Description

Nanolasers represents the research frontier in both the areas of photonics and nanotechnology for its interesting properties in low dimension physics, its appealing prospects in integrated photonics, and other on-chi

Nanolasers represents the research frontier in both the areas of photonics and nanotechnology for its interesting properties in low dimension physics, its appealing prospects in integrated photonics, and other on-chip applications. In this thesis, I present my research work on fabrication and characterization of a new type of nanolasers: metallic cavity nanolasers. The last ten years witnessed a dramatic paradigm shift from pure dielectric cavity to metallic cavity in the research of nanolasers. By using low loss metals such as silver, which is highly reflective at near infrared, light can be confined in an ultra small cavity or waveguide with sub-wavelength dimensions, thus enabling sub-wavelength cavity lasers. Based on this idea, I fabricated two different kinds of metallic cavity nanolasers with rectangular and circular geometries with InGaAs as the gain material and silver as the metallic shell. The lasing wavelength is around 1.55 μm, intended for optical communication applications. Continuous wave (CW) lasing at cryogenic temperature under current injection was achieved on devices with a deep sub-wavelength physical cavity volume smaller than 0.2 λ3. Improving device fabrication process is one of the main challenges in the development of metallic cavity nanolasers due to its ultra-small size. With improved fabrication process and device design, CW lasing at room temperature was demonstrated as well on a sub-wavelength rectangular device with a physical cavity volume of 0.67 λ3. Experiments verified that a small circular nanolasers supporting TE¬01 mode can generate an azimuthal polarized laser beam, providing a compact such source under electrical injection. Sources with such polarizations could have many special applications. Study of digital modulation of circular nanolasers showed that laser noise is an important factor that will affect the data rate of the nanolaser when used as the light source in optical interconnects. For future development, improving device fabrication processes is required to improve device performance. In addition, techniques need to be developed to realize nanolaser/Si waveguide integration. In essence, resolving these two critical issues will finally pave the way for these nanolasers to be used in various practical applications.

Contributors

Agent

Created

Date Created
  • 2014

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Modelling and simulation of plasmonic waveguides and nanolasers

Description

This thesis summarizes modeling and simulation of plasmonic waveguides and nanolasers. The research includes modeling of dielectric constants of doped semiconductor as a potential plasmonic material, simulation of plasmonic waveguides

This thesis summarizes modeling and simulation of plasmonic waveguides and nanolasers. The research includes modeling of dielectric constants of doped semiconductor as a potential plasmonic material, simulation of plasmonic waveguides with different configurations and geometries, simulation and design of plasmonic nanolasers. In the doped semiconductor part, a more accurate model accounting for dielectric constant of doped InAs was proposed. In the model, Interband transitions accounted for by Adachi's model considering Burstein-Moss effect and free electron effect governed by Drude model dominate in different spectral regions. For plasmonic waveguide part, Insulator-Metal-Insulator (IMI) waveguide, silver nanowire waveguide with and without substrate, Metal-Semiconductor-Metal (MSM) waveguide and Metal-Insulator-Semiconductor-Insulator-Metal (MISIM) waveguide were investigated respectively. Modal analysis was given for each part. Lastly, a comparative study of plasmonic and optical modes in an MSM disk cavity was performed by FDTD simulation for room temperature at the telecommunication wavelength. The results show quantitatively that plasmonic modes have advantages over optical modes in the scalability down to small size and the cavity Quantum Electrodynamics(QED) effects due to the possibility of breaking the diffraction limit. Surprisingly for lasing characteristics, though plasmonic modes have large loss as expected, minimal achievable threshold can be attained for whispering gallery plasmonic modes with azimuthal number of 2 by optimizing cavity design at 1.55µm due to interplay of metal loss and radiation loss.

Contributors

Agent

Created

Date Created
  • 2014