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Articles 1 - 12 of 12
Full-Text Articles in Physics
Femtosecond Laser Written Volumetric Diffractive Optical Elements And Their Applications, Jiyeon Choi
Femtosecond Laser Written Volumetric Diffractive Optical Elements And Their Applications, Jiyeon Choi
Electronic Theses and Dissertations
Since the first demonstration of femtosecond laser written waveguides in 1996, femtosecond laser direct writing (FLDW) has been providing a versatile means to fabricate embedded 3-D microstructures in transparent materials. The key mechanisms are nonlinear absorption processes that occur when a laser beam is tightly focused into a material and the intensity of the focused beam reaches the range creating enough free electrons to induce structural modification. One of the most useful features that can be exploited in fabricating photonic structures is the refractive index change which results from the localized energy deposition. The laser processing system for FLDW can …
Wavefront Sensor For Eye Aberrations Measurements, Costin Curatu
Wavefront Sensor For Eye Aberrations Measurements, Costin Curatu
Electronic Theses and Dissertations
Ocular wavefront sensing is vital to improving our understanding of the human eye and to developing advanced vision correction methods, such as adaptive optics, customized contact lenses, and customized laser refractive surgery. It is also a necessary technique for high-resolution imaging of the retina. The most commonly used wavefront sensing method is based on the Shack-Hartmann wavefront sensor. Since Junzhong Liang's first application of Shack-Hartmann wavefront sensing for the human eye in 1994, the method has quickly gained acceptance and popularity in the ophthalmic industry. Several commercial Shack-Hartmann eye aberrometers are currently available. While the existing aberrometers offer reasonable measurement …
Analysis And Design Of Wide-Angle Foveated Optical Systems, George Curatu
Analysis And Design Of Wide-Angle Foveated Optical Systems, George Curatu
Electronic Theses and Dissertations
The development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and complexity in fast wide-angle lenses. The fundamental concept behind optical foveated imaging is reducing the number of elements in a fast wide-angle lens by placing a phase SLM at the pupil stop to dynamically compensate …
Dense Spectral Beam Combining With Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Oleksiy Andrusyak
Dense Spectral Beam Combining With Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Oleksiy Andrusyak
Electronic Theses and Dissertations
Beam combining techniques have become an important tool in the design of high-power high-brightness laser systems. Spectral beam combining (SBC) is an incoherent combining technique that does not require phase control of sources, allowing for a stable and robust system. Using SBC, beams from an array of lasers with each element operated at a different wavelength are combined into a single near-diffraction-limited beam with the same aperture using dispersive optical elements. SBC by means of volume Bragg gratings (VBGs) utilizes unique spectral response of VBGs: diffraction efficiency is close to unity when the Bragg condition is satisfied and is close …
Design, Analysis, And Optimization Of Diffractive Optical Elements Under High Numerical Aperture Focusing, Toufic Jabbour
Design, Analysis, And Optimization Of Diffractive Optical Elements Under High Numerical Aperture Focusing, Toufic Jabbour
Electronic Theses and Dissertations
The demand for high optical resolution has brought researchers to explore the use of beam shaping diffractive optical elements (DOEs) for improving performance of high numerical aperture (NA) optical systems. DOEs can be designed to modulate the amplitude, phase and/or polarization of a laser beam such that it focuses into a targeted irradiance distribution, or point spread function (PSF). The focused PSF can be reshaped in both the transverse focal plane and along the optical axis. Optical lithography, microscopy and direct laser writing are but a few of the many applications in which a properly designed DOE can significantly improve …
Optical Nonlinear Interactions In Dielectric Nano-Suspensions, Ramy El-Ganainy
Optical Nonlinear Interactions In Dielectric Nano-Suspensions, Ramy El-Ganainy
Electronic Theses and Dissertations
This work is divided into two main parts. In the first part (chapters 2-7) we consider the nonlinear response of nano-particle colloidal systems. Starting from the Nernst-Planck and Smoluchowski equations, we demonstrate that in these arrangements the underlying nonlinearities as well as the nonlinear Rayleigh losses depend exponentially on optical intensity. Two different nonlinear regimes are identified depending on the refractive index contrast of the nanoparticles involved and the interesting prospect of self-induced transparency is demonstrated. Soliton stability is systematically analyzed for both 1D and 2D configurations and their propagation dynamics in the presence of Rayleigh losses is examined. We …
Gabor Domain Optical Coherence Microscopy, Supraja Murali
Gabor Domain Optical Coherence Microscopy, Supraja Murali
Electronic Theses and Dissertations
Time domain Optical Coherence Tomography (TD-OCT), first reported in 1991, makes use of the low temporal coherence properties of a NIR broadband laser to create depth sectioning of up to 2mm under the surface using optical interferometry and point to point scanning. Prior and ongoing work in OCT in the research community has concentrated on improving axial resolution through the development of broadband sources and speed of image acquisition through new techniques such as Spectral domain OCT (SD-OCT). In SD-OCT, an entire depth scan is acquired at once with a low numerical aperture (NA) objective lens focused at a fixed …
Power Scaling Of Large Mode Area Thulium Fiber Lasers In Various Spectral And Temporal Regimes, Timothy Mccomb
Power Scaling Of Large Mode Area Thulium Fiber Lasers In Various Spectral And Temporal Regimes, Timothy Mccomb
Electronic Theses and Dissertations
High power thulium fiber lasers are interesting for a myriad of applications due to their potential for high average output power, excellent beam quality, compactness, portability, high operating efficiency and broad, eye-safe spectral range from 1.8-2.1 microns. Currently, the majority of thulium laser research effort is being invested into scaling average output powers; however, such output powers are being scaled with no degree of control on laser system output spectrum or temporal behavior. Thulium fiber laser technology is not useful for many of its most important applications without implementation of techniques enabling tunable, narrow spectral widths with appropriate pulse durations …
Silicon Carbide And Agile Optics Based Sensors For Power Plant Gas Turbines, Laser Beam Analysis And Biomedicine, Mumtaz Sheikh
Silicon Carbide And Agile Optics Based Sensors For Power Plant Gas Turbines, Laser Beam Analysis And Biomedicine, Mumtaz Sheikh
Electronic Theses and Dissertations
Proposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing method that combines wavelength-tuned signal processing for coarse measurements and classical FP etalon peak shift for fine measurements is proposed and demonstrated. This method gives direct unambiguous temperature measurements with …
Design And Fabrication Of Space Variant Micro Optical Elements, Pradeep Srinivasan
Design And Fabrication Of Space Variant Micro Optical Elements, Pradeep Srinivasan
Electronic Theses and Dissertations
A wide range of applications currently utilize conventional optical elements to individually transform the phase, polarization, and spectral transmission/reflection of the incident radiation to realize the desired system level function. The material properties and the feasibility of fabrication primarily impact the device and system functionality that can be realized. With the advancement in micro/nano patterning, growth, deposition and etching technology, devices with novel and multiplexed optical functionalities have become feasible. As a result, it has become possible to engineer the device response in the near and far field by controlling the phase, polarization or spectral response at the micro scale. …
Wavelength-Division-Multiplexed Transmission Using Semiconductor Optical Amplifiers And Electronic Impairment Compensation, Xiaoxu Li
Electronic Theses and Dissertations
Over the last decade, rapid growth of broadband services necessitated research aimed at increasing transmission capacity in fiber-optic communication systems. Wavelength division multiplexing (WDM) technology has been widely used in fiber-optic systems to fully utilize fiber transmission bandwidth. Among optical amplifiers for WDM transmission, semiconductor optical amplifier (SOA) is a promising candidate, thanks to its broad bandwidth, compact size, and low cost. In transmission systems using SOAs, due to their large noise figures, high signal launching powers are required to ensure reasonable optical signal-to-noise ratio of the received signals. Hence the SOAs are operated in the saturation region and the …
Nonlinear Femtosecond Near Infrared Laser Structuring In Oxide Glasses, Arnaud Royon
Nonlinear Femtosecond Near Infrared Laser Structuring In Oxide Glasses, Arnaud Royon
Electronic Theses and Dissertations
Three-dimensional femtosecond laser structuring has a growing interest because of its ease of implementation and the numerous possible applications in the domain of photonic components. Structures such as waveguides, diffraction gratings, optical memories or photonic crystals can be fabricated thanks to this technique. Its use with oxide glasses is promising because of several advantages; they are resistant to flux and ageing, their chemical composition can easily be changed to fit the well-defined requirements of an application. They can already be found in Raman amplifiers, optical fibers, fiber lasers, and other devices. This thesis is based on two axes. The first …