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- Title
- Filament Plasma Density Enhancement Using Two Co-Propagating Beams.
- Creator
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Pena, Jessica, Richardson, Martin, Moharam, Jim, Gaume, Romain, Rostami Fairchild, Shermineh, University of Central Florida
- Abstract / Description
-
Filaments are self-guided plasma channels generated from laser pulses with power above a critical value. They can propagate several times the Rayleigh length for diffraction and can travel through adverse atmospheric conditions. As such, filaments are useful in applications such as long wavelength electromagnetic and electric discharge guiding, and weather manipulation to name a few. Arrays of filaments can be useful to these applications, particularly in the generation of waveguides. However...
Show moreFilaments are self-guided plasma channels generated from laser pulses with power above a critical value. They can propagate several times the Rayleigh length for diffraction and can travel through adverse atmospheric conditions. As such, filaments are useful in applications such as long wavelength electromagnetic and electric discharge guiding, and weather manipulation to name a few. Arrays of filaments can be useful to these applications, particularly in the generation of waveguides. However, understanding the filament-induced plasma dynamics of two closely propagating beams is crucial in designing the ideal waveguide. One common way to characterize a filament is through the electron density of the plasma channel, a property which has previously been proven to be clamped for a single filament. This work will show how the electron density can be enhanced through the use of two co-propagating beams, taking advantage of their interaction. Three cases were studied: two sub-critical beams, one subcritical beam and one filament, and two filaments. The separations and focusing conditions of the beams were also varied. Enhancement of the electron density and lengthening of the plasma lifetime will be discussed for each case.
Show less - Date Issued
- 2019
- Identifier
- CFE0007702, ucf:52436
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007702
- Title
- Fundamental Properties of Metallic Nanolasers.
- Creator
-
Hayenga, William, Khajavikhan, Mercedeh, Christodoulides, Demetrios, Likamwa, Patrick, Abdolvand, Reza, University of Central Florida
- Abstract / Description
-
The last two decades have witnessed tremendous advancements in the area of nanophotonics and plasmonics, which has helped propel the development of integrated photonic sources. Of central importance to such circuits is compact, scalable, low threshold, and efficient coherent sources that can be driven at high modulation frequencies. In this regard, metallic nanolasers offer a unique platform. Their introduction has enabled confinement of light at a subwavelength scale and the ultra-small size...
Show moreThe last two decades have witnessed tremendous advancements in the area of nanophotonics and plasmonics, which has helped propel the development of integrated photonic sources. Of central importance to such circuits is compact, scalable, low threshold, and efficient coherent sources that can be driven at high modulation frequencies. In this regard, metallic nanolasers offer a unique platform. Their introduction has enabled confinement of light at a subwavelength scale and the ultra-small size of the modes afforded by these structures allows for cavity enhancing effects that can help facilitate thresholdless lasing and large direct modulation bandwidths. In this report, I present my work on the study of the fundamental properties of metallic nanolasers. I start with a rate equation model to predict threshold behavior and the modulation response of metallic nanolasers. Next, I explain the second-order coherence measurement setup that was built, based on a modified Hanbury-Brown and Twiss experiment, to assess the intensity autocorrelation of various optically pumped metallic nanolasers. These studies concluded that metallic coaxial and disk-shaped nanolasers are capable of generating truly coherent radiation. Subsequently, design considerations are taken into account for electrically pumped coaxial nanolasers. This has led to the demonstration of electrically injected coaxial and disk-shaped nanolasers at cryogenic temperatures. Lastly, the appearance of collective behaviors in metallic nanolasers lattices is explored. Individually supporting modes that are highly vectorial by nature, when such cavities are fabricated in close proximity to one another, coupling through their overlapping fields results in the formation of a set of supermodes. The tendency of the system to minimize the overall loss leads to each element of the lattice having a geometric dependent field distribution and helps promotes single-mode lasing. We show both through simulations and experimentally that this effect can lead to the direct generation of vector vortices.
Show less - Date Issued
- 2018
- Identifier
- CFE0007752, ucf:52391
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007752
- Title
- CHARACTERIZATION AND MODELING OF A HIGH POWER THIN DISK LASER.
- Creator
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Rodriguez-Valls, Omar, Richardson, Martin, University of Central Florida
- Abstract / Description
-
High power lasers have been adapted to material processing, energy, military and medical applications. In the Laser Plasma Laboratory at CREOL, UCF, high power lasers are used to produce highly ionized plasmas to generate EUV emission. This thesis examines the quality of a recently acquired high power thin disk laser through thermal modeling and beam parameter measurements. High power lasers suffer from thermally induced issues which degrade their operation. Thin disk lasers use an innovative...
Show moreHigh power lasers have been adapted to material processing, energy, military and medical applications. In the Laser Plasma Laboratory at CREOL, UCF, high power lasers are used to produce highly ionized plasmas to generate EUV emission. This thesis examines the quality of a recently acquired high power thin disk laser through thermal modeling and beam parameter measurements. High power lasers suffer from thermally induced issues which degrade their operation. Thin disk lasers use an innovative heat extraction mechanism that eliminates the transverse thermal gradient within the gain medium associated with thermal lensing. A thorough review of current thin disk laser technology is described. Several measurement techniques were performed on a high power thin disk laser. The system efficiencies, spectrum, and temporal characteristics were examined. The laser was characterized in the far-field regime to determine the beam quality and intensity of the laser. Laser cavity simulations of the thin disk laser were performed using LASCAD. The induced thermal and stress effects are demonstrated. Simulated output power and efficiency is compared to those that have been quantified experimentally.
Show less - Date Issued
- 2010
- Identifier
- CFE0003216, ucf:48578
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003216
- Title
- Power Scaling of High Power Solid State Lasers.
- Creator
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Oh, Bumjin, Richardson, Martin, Soileau, MJ, Chini, Michael, University of Central Florida
- Abstract / Description
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The solid-state laser is one of the most widely used lasers in scientific research and industrial applications. This thesis describes detailed investigations of two modern architectures of high power cw solid-state lasers, a 20 W diode-pumped Yb:YAG thin disc laser and 300 W diode-pumped Nd:YAG rod laser. With the thin disc laser architecture, the signal beam must fit to the pump area on the disc defined by the multi-pass diode pump configuration. The beam propagation, beam diameter, phase...
Show moreThe solid-state laser is one of the most widely used lasers in scientific research and industrial applications. This thesis describes detailed investigations of two modern architectures of high power cw solid-state lasers, a 20 W diode-pumped Yb:YAG thin disc laser and 300 W diode-pumped Nd:YAG rod laser. With the thin disc laser architecture, the signal beam must fit to the pump area on the disc defined by the multi-pass diode pump configuration. The beam propagation, beam diameter, phase and thermal effects for various cavity configurations are investigated theoretically and experimentally. In addition, the internal loss, small signal gain, and thermal lensing effect are essential properties to construct the laser system but usually unknown. The theories and methodologies to obtain these properties are presented and the experimental results are compared. In a second phase of the project, the multi-mode and single-mode operation of a high power diode-pumped rod laser system are examined and compared to the thin disc system. Thermal effects on the phase, beam quality and brightness are examined and future applications and improvements considered.
Show less - Date Issued
- 2018
- Identifier
- CFE0007232, ucf:52221
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007232
- Title
- Laser Filamentation Interaction with Materials for Spectroscopic Applications.
- Creator
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Weidman, Matthew, Richardson, Martin, Schulzgen, Axel, Christodoulides, Demetrios, Sigman, Michael, University of Central Florida
- Abstract / Description
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Laser filamentation is a non-diffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work has shown a quasi-constant filament-induced mass ablation along a 35 m propagation distance. The mass ablated was sufficient for the application of...
Show moreLaser filamentation is a non-diffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work has shown a quasi-constant filament-induced mass ablation along a 35 m propagation distance. The mass ablated was sufficient for the application of laser filamentation as a sampling tool for plasma based spectroscopy techniques. Within the scope of this study, single-shot ablation was compared with multi-shot ablation. The dependence of ablated mass on the number of pulses was observed to have a quasi-linear dependence on the number of pulses, advantageous for applications such as spectroscopy. Sample metrology showed that both physical and optical material properties have significant effects on the filament-induced ablation behavior. A relatively slow filament-induced plasma expansion was observed, as compared with a focused beams. This suggests that less energy was transferred to the plasma during filament-induced ablation. The effects of the filament core and the energy reservoir on the filament-induced ablation and plasma formation were investigated. Goniometric measurements of the filament-induced plasma, along with radiometric calculations, provided the number of emitted photons from a specific atomic transition and sample material.This work has advanced the understanding of the effects of single filaments on the ablation of solid materials and the understanding of filament-induced plasma dynamics. It has laid the foundation for further quantitative studies of multiple filamentation. The implications of this work extend beyond spectroscopy and included any application of filamentation that involves the interaction with a solid material.
Show less - Date Issued
- 2012
- Identifier
- CFE0004616, ucf:49940
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004616
- Title
- POWER SCALING OF LARGE MODE AREA THULIUM FIBER LASERS IN VARIOUS SPECTRAL AND TEMPORAL REGIMES.
- Creator
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McComb, Timothy, Richardson, Martin, University of Central Florida
- Abstract / Description
-
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...
Show moreHigh 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 for particular applications. This work outlines several techniques for spectral control of thulium fiber lasers and investigates scaling of average laser powers while using these techniques to maintain a desired spectral output. In addition, an examination of operation in both nanosecond and picosecond pulsed regimes and scaling of average powers and pulse energies in these regimes to useful power levels is conducted. The demonstration of thulium fiber laser systems for applications in frequency conversion and spectral beam combination is also discussed. In addition to the experimental results, theoretical modeling of thulium fiber amplifier operation, simple thermal management analysis, as well as practical fiber and system design considerations for future power scaling are presented. Experimental and theoretical results of this work will enable the successful design of future extremely high power spectrally and temporally controlled thulium fiber laser systems.
Show less - Date Issued
- 2009
- Identifier
- CFE0002885, ucf:48045
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002885
- Title
- High Power Continuous Wave Quantum Cascade Lasers With Increased Ridge Width.
- Creator
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Todi, Ankesh, Lyakh, Arkadiy, Huo, Qun, Tetard, Laurene, University of Central Florida
- Abstract / Description
-
Quantum Cascade Lasers have recently gained considerable attention for their capability to emit infrared radiation in a broad infrared spectral region, very compact dimensions, and high optical power/efficiency. Increasing continuous wave optical power is one of the main research directions in the field. A straightforward approach to increasing optical power in the pulsed regime is to increase number of stages in the cascade structure. However, due to a low active region thermal conductivity,...
Show moreQuantum Cascade Lasers have recently gained considerable attention for their capability to emit infrared radiation in a broad infrared spectral region, very compact dimensions, and high optical power/efficiency. Increasing continuous wave optical power is one of the main research directions in the field. A straightforward approach to increasing optical power in the pulsed regime is to increase number of stages in the cascade structure. However, due to a low active region thermal conductivity, the increase in number of stages leads to active region overheating in continuous wave operation. In this work, an alternative approach to power scaling with device dimensions is explored: number of stages is reduced to reduce active region thermal resistance, while active region lateral size is increased for reaching high optical power level. Using this approach, power scaling for active region width increase from 10(&)#181;m to 20(&)#181;m is demonstrated for the first time. An analysis based on a simple semi-empirical model suggests that laser power can be significantly improved by increasing characteristic temperature T0 that describes temperature dependence of laser threshold current density.
Show less - Date Issued
- 2017
- Identifier
- CFE0007137, ucf:52299
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007137
- Title
- LASER FILAMENT INTERACTION WITH AEROSOLS AND CLOUDS.
- Creator
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Jeon, Cheonha, Richardson, Martin, Vanstryland, Eric, Baudelet, Matthieu, Sigman, Michael, University of Central Florida
- Abstract / Description
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A high powered ultrashort laser pulse can propagate as a diffraction-free self-channeled structure called a filament, created by a combination of nonlinear processes. With its ability to convey extremely high intensity beams to distant targets, many applications such as remote sensing, cloud seeding, and discharge guiding are potentially possible. However, one of the main challenges of outdoor field applications is the laser propagation through the atmosphere where pressure fluctuations and...
Show moreA high powered ultrashort laser pulse can propagate as a diffraction-free self-channeled structure called a filament, created by a combination of nonlinear processes. With its ability to convey extremely high intensity beams to distant targets, many applications such as remote sensing, cloud seeding, and discharge guiding are potentially possible. However, one of the main challenges of outdoor field applications is the laser propagation through the atmosphere where pressure fluctuations and concentrations of aerosols may be present. The rationale behind the work presented in this dissertation is to evaluate the robustness of the filamentation, measure the interaction losses as well as understanding the modifications to (i) filament length (ii) supercontinuum generation, and (iii) the beam profile along propagation through perturbed media.Detailed studies of the interaction of a single filament with a single water droplet are presented. In addition, preliminary results on filament propagation through a cloud of aerosols are discussed. The effect of pressure on the beam profile along propagation and on the supercontinuum generated by the filament is studied. This document provides valuable insight into the complex nonlinear processes affecting the formation, propagation and post propagation of filaments under adverse atmospheric conditions.
Show less - Date Issued
- 2016
- Identifier
- CFE0006530, ucf:51368
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006530
- Title
- Design and Engineering of Ultrafast Amplifier Systems.
- Creator
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Webb, Benjamin, Richardson, Martin, Chang, Zenghu, Delfyett, Peter, Gaume, Romain, Shah, Lawrence, Klemm, Richard, University of Central Florida
- Abstract / Description
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Recently, the design and engineering of ultrafast laser systems have led to an extraordinary increase in laser power and performance which have brought about advances in many fields such as medicine, material processing, communications, remote sensing, spectroscopy, nonlinear optics, and atomic physics. In this work, several ultrafast amplification techniques -- including chirped-pulse amplification (CPA), optical parametric chirped-pulse amplification (OPCPA), and divided-pulse amplification...
Show moreRecently, the design and engineering of ultrafast laser systems have led to an extraordinary increase in laser power and performance which have brought about advances in many fields such as medicine, material processing, communications, remote sensing, spectroscopy, nonlinear optics, and atomic physics. In this work, several ultrafast amplification techniques -- including chirped-pulse amplification (CPA), optical parametric chirped-pulse amplification (OPCPA), and divided-pulse amplification (DPA) -- are described and demonstrated in the design and construction of two ultrafast laser facilities. An existing Ti:Sapphire laser system was completely redesigned with an increased power of 10 TW for experiments capable of generating hundreds of laser filaments in ordered arrays. The performance of DPA above the Joule-level was investigated in a series of experiments utilizing various DPA schemes with gain-saturated amplifiers at high pulse energy. A new high energy OPCPA facility has been designed and its pump laser system constructed, utilizing the technique of DPA for the first time in a flashlamp-pumped amplifier chain and with a record combined energy of 5 Joules in a 230 ps pulse duration. The demonstrated OPCPA pump performance will allow for the generation of 50 TW quasi-single cycle 5 fs pulses at 2.5 Hz from a table-top OPCPA system.
Show less - Date Issued
- 2016
- Identifier
- CFE0006547, ucf:51349
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006547
- Title
- A MOBILE ROBOTIC COMPUTING PLATFORM FOR THREE-DIMENSIONAL INDOOR MAPPING AND DATABASE BUILDING.
- Creator
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McCoig, Kenneth, Schiavone, Guy, University of Central Florida
- Abstract / Description
-
There are several industries exploring solutions to quickly and accurately digitize unexplored indoor environments, into useable three-dimensional databases. Unfortunately, there are inherent challenges to the indoor mapping process such as, scanning limitations and environment complexity, which require a specific application of tools to map an environment precisely with low cost and high speed. This thesis successfully demonstrates the design and implementation of a low cost mobile robotic...
Show moreThere are several industries exploring solutions to quickly and accurately digitize unexplored indoor environments, into useable three-dimensional databases. Unfortunately, there are inherent challenges to the indoor mapping process such as, scanning limitations and environment complexity, which require a specific application of tools to map an environment precisely with low cost and high speed. This thesis successfully demonstrates the design and implementation of a low cost mobile robotic computing platform with laser scanner, for quickly mapping with high resolution, urban and/or indoor environments using a gyro-enhanced orientation sensor and selectable levels of detail. In addition, a low cost alternative solution to three-dimensional laser scanning is presented, via a standard two-dimensional SICK proximity laser scanner mounted to a custom servo motor mount and controlled by external microcontroller. A software system to control the robot is presented, which incorporates and adheres to widely accepted software engineering guidelines and principles. An analysis of the overall system, including robot specifications, system capabilities, and justification for certain design decisions, are described in detail. Results of various open source software algorithms, as it applies to scan data and image data, are also compared; including evaluation of data correlation and registration techniques. In addition, laser scanner mapping tests, specifications, and capabilities are presented and analyzed. A sample design for converting the final scanned point cloud data to a database is presented and assessed. The results suggest the overall project yields a relatively high degree of accuracy and lower cost over most other existing systems surveyed, as well as, the potential for application of the system in other fields. The results also discuss thoughts for possible future research work.
Show less - Date Issued
- 2004
- Identifier
- CFE0000313, ucf:46317
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000313
- Title
- CHOLESTERIC LIQUID CRYSTAL PHOTONIC CRYSTAL LASERS AND PHOTONIC DEVICES.
- Creator
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Zhou, Ying, Wu, Shin-Tson, University of Central Florida
- Abstract / Description
-
This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser...
Show moreThis dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser emission is further demonstrated in a hybrid photonic band edge - Fabry-Perot (FP) type structure by sandwiching the CLC active layer within a circular polarized resonator consisting of two CLC reflectors. The resonator generates multiple FP modes while preserving the PBE mode from the active layer. More importantly this band edge mode can be greatly enhanced by the external resonator under some conditions. Theoretical analysis is conducted based on 4×4 transfer matrix and scattering matrix and the results are consistent with our experimental observations. To make the CLC laser more compact and miniaturized, we have developed a flexible polymer laser using dye-doped cholesteric polymeric films. By stacking the mirror reflecting layer, the active layer and the CLC reflecting layer, enhanced laser emission was observed in opposite-handed circular polarization state, because of the light recycling effect. On the other hand, we use the stacked cholesteric liquid crystal films, or the cholesteric liquid crystals and polymer composite films to demonstrate the single film broadband circular polarizers, which are helpful for converting a randomly polarized light into linear polarization. New fabrication methods are proposed and the circular polarizers cover ~280 nm in the visible spectral range. Both theoretical simulation and experimental results are presented with a good match.
Show less - Date Issued
- 2008
- Identifier
- CFE0002198, ucf:47891
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002198
- Title
- 2 micron fiber lasers: power scaling concepts and limitations.
- Creator
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Sincore, Alex, Richardson, Martin, Amezcua Correa, Rodrigo, Schulzgen, Axel, Shah, Lawrence, University of Central Florida
- Abstract / Description
-
Thulium- and holmium-doped fiber lasers (TDF and HDF) emitting at 2 micron offer unique benefits and applications compared to common ytterbium-doped 1 micron lasers. This dissertation details the concepts, limitations, design, and performance of four 2 micron fiber laser systems. While these lasers were developed for various end-uses, they also provide further insight into two major power scaling limitations. The first limitation is optical nonlinearities: specifically stimulated Brillouin...
Show moreThulium- and holmium-doped fiber lasers (TDF and HDF) emitting at 2 micron offer unique benefits and applications compared to common ytterbium-doped 1 micron lasers. This dissertation details the concepts, limitations, design, and performance of four 2 micron fiber laser systems. While these lasers were developed for various end-uses, they also provide further insight into two major power scaling limitations. The first limitation is optical nonlinearities: specifically stimulated Brillouin scattering (SBS) and modulation instability (MI). The second limitation is thermal failure due to inefficient pump conversion. First, a 21.5 W single-frequency, single-mode laser with adjustable output from continuous-wave to nanosecond pulses is developed. Measuring the SBS threshold versus pulse duration enables the Brillouin gain coefficient and gain bandwidth to be determined at 2 micron. Second, a 23 W spectrally-broadband, nanosecond pulsed laser is constructed for materials processing applications. The temporally incoherent multi-kW peak power pulses can also efficiently produce MI and supercontinuum generation by adjusting the input spectral linewidth. Third, the measured performance of in-band pumped TDF and HDF lasers are compared with simulations. HDF displays low efficiencies, which is explained by including ion clustering in the simulations. The TDF operates with impressive (>)90% slope efficiencies. Based on this result, a system design for (>)1 kW average power TDF amplifier is described. The designed final amplifier will be in-band pumped to enable high efficiency and low thermal load. The amplifier efficiency, operating bandwidth, thermal load, and nonlinear limits are modeled and analyzed to provide a framework for execution. Overall, this dissertation provides further insight and understanding on the various processes that limit power scaling of 2 micron fiber lasers.
Show less - Date Issued
- 2018
- Identifier
- CFE0007374, ucf:52105
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007374
- Title
- Design and Engineering Criteria for Optical Parametric Chirped Pulse Amplifier Systems.
- Creator
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Bodnar, Nathan, Richardson, Martin, Delfyett, Peter, Likamwa, Patrick, Baudelet, Matthieu, Shah, Lawrence, University of Central Florida
- Abstract / Description
-
The generation of a quasi-single-cycle laser light pulse is a goal in many laser applications experiments. Some involve in High Harmonic Generation (HHG) and Attosecond Sciences. The demand for ultrafast laser facilities has grown; the techniques and availability of materials have changed; thereby posing new design challenges in building Optical Parametric Chirped Pulse Amplification (OPCPA) laser facilities. The concepts and challenges are discussed in detail in the development of two laser...
Show moreThe generation of a quasi-single-cycle laser light pulse is a goal in many laser applications experiments. Some involve in High Harmonic Generation (HHG) and Attosecond Sciences. The demand for ultrafast laser facilities has grown; the techniques and availability of materials have changed; thereby posing new design challenges in building Optical Parametric Chirped Pulse Amplification (OPCPA) laser facilities. The concepts and challenges are discussed in detail in the development of two laser systems within the Laser Plasma Laboratory, HERACLES and PhaSTHEUS. This dissertation also gives insight to the challenges that are encountered in other cutting edge OPCPA laser facilities. An overview of the design challenges that need to be addressed in any OPCPA laser facility either high energy or high average power that is suitable for high intensity laser physics is discussed in this dissertation.
Show less - Date Issued
- 2018
- Identifier
- CFE0007158, ucf:52300
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007158
- Title
- Multiscale simulation of laser ablation and processing of semiconductor materials.
- Creator
-
Shokeen, Lalit, Schelling, Patrick, Kar, Aravinda, Vaidyanathan, Rajan, Su, Ming, Kara, Abdelkader, University of Central Florida
- Abstract / Description
-
We present a multiscale model of laser-solid interactions in silicon based on an empirical potential developed under conditions of strong electronic excitations. The parameters of the interatomic potential depends on the temperature of the electronic subsystem Te, which is directly related to the density of the electron-hole pairs and hence the number of broken bonds. We analyze the dynamics of this potential as a function of electronic temperature Te and lattice temperature Tion. The...
Show moreWe present a multiscale model of laser-solid interactions in silicon based on an empirical potential developed under conditions of strong electronic excitations. The parameters of the interatomic potential depends on the temperature of the electronic subsystem Te, which is directly related to the density of the electron-hole pairs and hence the number of broken bonds. We analyze the dynamics of this potential as a function of electronic temperature Te and lattice temperature Tion. The potential predicts phonon spectra in good agreement with finite-temperature density-functional theory (DFT), including the lattice instability induced by the high electronic excitations. For 25fs pulse, a wide range of fluence values is simulated resulting in heterogeneous melting, homogenous melting, and ablation. The results presented demonstrate that phase transitions can usually be described by ordinary thermal processes even when the electronic temperature Te is much greater than the lattice temperature TL during the transition. However, the evolution of the system and details of the phase transitions depend strongly on Te and corresponding density of broken bonds. For high enough laser fluence, homogeneous melting is followed by rapid expansion of the superheated liquid and ablation. Rapid expansion of the superheated liquid occurs partly due to the high pressures generated by a high density of broken bonds. As a result, the system is readily driven into the liquid-vapor coexistence region, which initiates phase explosion. The results strongly indicates that phase explosion, generally thought of as an ordinary thermal process, can occur even under strong non-equilibrium conditions when Te (>)(>)TL. In summary, a detailed investigation of laser-solid interactions in silicon is presented for femtosecond laser pulse that yields strong far-from-equilibrium conditions.
Show less - Date Issued
- 2012
- Identifier
- CFE0004599, ucf:49206
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004599
- Title
- PHOTODISRUPTION IN OCULAR TISSUE NEAR AND AT THE BOUNDARY BETWEEN THE ANTERIOR CHAMBER AND CRYSTALLINE LENS.
- Creator
-
Olmstead, Richard, Richardson, Martin, University of Central Florida
- Abstract / Description
-
Lasers have been involved in Ophthalmology in the treatment of myopia and hyperopia for several years. Laser systems have transformed patients' quality of life, freeing them from the need for glasses, as in the case of LASIK. Ultrafast lasers have played an important role in surgery of the eye. In LASIK, they are used to cut the flap that is lifted to expose the stroma for UV Excimer laser treatment of this region. They are now being used for surgery deeper into the eye,for instance, treating...
Show moreLasers have been involved in Ophthalmology in the treatment of myopia and hyperopia for several years. Laser systems have transformed patients' quality of life, freeing them from the need for glasses, as in the case of LASIK. Ultrafast lasers have played an important role in surgery of the eye. In LASIK, they are used to cut the flap that is lifted to expose the stroma for UV Excimer laser treatment of this region. They are now being used for surgery deeper into the eye,for instance, treating the lens as part of treatments for cataract surgery. The use of ultrafast lasers in cataract surgery and how they can be applied to achieve better surgical outcomes is the focus of this work. It reports on an investigation of laser interaction at and near the anterior of the lens, in particular the boundary between the fibrous mass, capsule, and anterior chamber of the eye. The study reviews the biomechanics of the eye, develops an interaction model with lens tissue, and reports for the first time clinically studies using ex vivo testing of porcine eyes. The components of the treatment laser system are described along with the requirements. Results of the experiments are outlined and discussed, followed by a summary and conclusions including discussion of areas for further research.
Show less - Date Issued
- 2011
- Identifier
- CFE0003658, ucf:48817
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003658
- Title
- Electrical Parasitic Bandwidth Limitations of Oxide-Free Lithographic Vertical-Cavity Surface-Emitting Lasers.
- Creator
-
Yang, Xu, Deppe, Dennis, Fathpour, Sasan, Wu, Shintson, Gong, Xun, University of Central Florida
- Abstract / Description
-
Nowadays, Vertical-Cavity Surface-Emitting Lasers (VCSELs) are the most popular optical sources in short-reach data communications. In the commercial oxide VCSEL technology, an oxide aperture is created inside resonant cavity in realizing good mode and current confinement, however, high electrical resistance comes along with forming the oxide aperture and the electrical parasitic bandwidth becomes the main limitation in modulation speed. In this report, electrical bandwidths of oxide-free...
Show moreNowadays, Vertical-Cavity Surface-Emitting Lasers (VCSELs) are the most popular optical sources in short-reach data communications. In the commercial oxide VCSEL technology, an oxide aperture is created inside resonant cavity in realizing good mode and current confinement, however, high electrical resistance comes along with forming the oxide aperture and the electrical parasitic bandwidth becomes the main limitation in modulation speed. In this report, electrical bandwidths of oxide-free lithographic VCSELs have been studied along with their general lasing properties. Due to the new ways of fabricating the aperture, record low resistances have been achieved in oxide-free lithographic VCSELs with various sizes, while high slope efficiencies and high output powers have been maintained. High speed simulation has been performed showing the very low differential resistances will benefit much to the electrical parasitic bandwidths, and are expected to produce higher modulation speed. A bottom emitting structure has been proposed and analyzed, showing reduction in both mirror resistance and capacitance will further improve the modulation speed. The total 3-dB modulation bandwidth is expected to be 50-80 GHz, much higher than the bandwidth reached in existing oxide VCSELs. Lithographic VCSELs also show superior lasing characteristics, including record low thermal resistance and record high output power. The maximum power exceeds 19 mW in a 6 (&)#181;m device and over 50 % power conversion efficiency has been achieved. A maximum single mode operation power of 5 mW has been observed from a 1 (&)#181;m diameter VCSEL. High temperature stress testing has been performed showing lithographic VCSELs can operate more reliably than oxide VCSELs under extreme operating conditions. Lithographic VCSEL with low electrical resistance, single-mode operation, high efficiency, and high power will be a strong candidate as the optical source in high speed data communications, as well as other applications such as high power VCSEL arrays and optical sensing.
Show less - Date Issued
- 2016
- Identifier
- CFE0006425, ucf:51491
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006425
- Title
- High Average Power Nanosecond Pulsed Tm:Fiber Laser for Pumping an Optical Parametric Oscillator.
- Creator
-
Abdulfattah, Ali, Richardson, Martin, Shah, Lawrence, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
Thulium-doped fiber lasers operating with wavelengths in the vicinity of 2 (&)#181;m are useful for several emerging applications including generating mid-IR light via nonlinear frequency conversion. In this study we describe the design and construction of a thulium fiber laser system comprising a master oscillator and a power amplifier. The first stage is a Q-switched, thulium-doped photonic crystal fiber oscillator utilizing an acousto-optic modulator to produce 65-80 nanosecond pulses. A...
Show moreThulium-doped fiber lasers operating with wavelengths in the vicinity of 2 (&)#181;m are useful for several emerging applications including generating mid-IR light via nonlinear frequency conversion. In this study we describe the design and construction of a thulium fiber laser system comprising a master oscillator and a power amplifier. The first stage is a Q-switched, thulium-doped photonic crystal fiber oscillator utilizing an acousto-optic modulator to produce 65-80 nanosecond pulses. A diffraction grating in the cavity provides wavelength tunability from 1.8 (-) 2?m. The oscillator produced up to 3 W of average power and 150 (&)#181;J pulse energies, corresponding to 2.3 kW peak powers. The amplifier stage consists of a large mode area, thulium-doped, step-index fiber seeded with powers up to 2 W from the oscillator. An output energy of 700 (&)#181;J with 81 ns pulse width, was achieved at a wavelength of 1.9 (&)#181;m. The effect of the fiber holder temperature on the amplifier performance relative to output pulse energy and seed wavelength was also studied. As a part of this thesis, a methodology has been developed to thoroughly characterize Tm:fiber amplifier performance. This has been the subject of prior work by several research groups, however, this work explicitly focuses on the precise characterization of absorbed pump power, pump bleaching, and extracted amplified energy for a range of input seeds power, pulse energy, and wavelength in order to better understand amplifier performance.
Show less - Date Issued
- 2016
- Identifier
- CFE0006240, ucf:51065
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006240
- Title
- Design of a hydrogen-filled hollow-core Raman fiber laser.
- Creator
-
Qin, Yangyang, Amezcua Correa, Rodrigo, Schulzgen, Axel, Shah, Lawrence, University of Central Florida
- Abstract / Description
-
The purpose of this study is to investigate the design of a Raman fiber laser based on a molecule hydrogen-filled hollow-core fiber with non-touching single ring of capillaries structure. O-hydrogen vibrational frequency shift of 4155 cm-1 and rotational frequency shift of 587 cm-1 were employed to generate Raman scattering from a 1064nm pump source.A thorough exploration was made to show how all Raman fiber laser components made up: gas chamber, hollow-core fibers, windows. The whole process...
Show moreThe purpose of this study is to investigate the design of a Raman fiber laser based on a molecule hydrogen-filled hollow-core fiber with non-touching single ring of capillaries structure. O-hydrogen vibrational frequency shift of 4155 cm-1 and rotational frequency shift of 587 cm-1 were employed to generate Raman scattering from a 1064nm pump source.A thorough exploration was made to show how all Raman fiber laser components made up: gas chamber, hollow-core fibers, windows. The whole process of chamber design, modification and fabrication were demonstrated. Besides, two kinds of anti-resonant hollow-core fibers were studied and tested. The transmission and loss spectrum of these fibers were measured thus it's easier to make a choice. Through the whole thesis a Raman fiber laser can be set up and tested very soon.
Show less - Date Issued
- 2017
- Identifier
- CFE0006645, ucf:51213
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006645
- Title
- DISPERSION-MANAGED BREATHING-MODE SEMICONDUCTOR MODE-LOCKED RING LASER: EXPERIMENTAL STUDY, NUMERICAL SIMULATIONS AND APPLICATIONS.
- Creator
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Resan, Bojan, Delfyett, Peter J., University of Central Florida
- Abstract / Description
-
A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching...
Show moreA novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated.
Show less - Date Issued
- 2004
- Identifier
- CFE0000176, ucf:46155
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000176
- Title
- EXTERNAL CAVITY MULTIWAVELENGTH SEMICONDUCTOR MODE-LOCKED LASER GAIN DYNAMICS.
- Creator
-
Archundia-Berra, Luis, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
External cavity semiconductor mode-locked lasers can produce pulses of a few picoseconds. The pulses from these lasers are inherently chirped with a predominant linear chirp component that can be compensated resulting in sub-picosecond pulses. External cavity semiconductor mode-locked lasers can be configured as multiwavelength pulse sources and are good candidates for time and wavelength division multiplexing applications. The gain medium in external cavity semiconductor mode-locked lasers...
Show moreExternal cavity semiconductor mode-locked lasers can produce pulses of a few picoseconds. The pulses from these lasers are inherently chirped with a predominant linear chirp component that can be compensated resulting in sub-picosecond pulses. External cavity semiconductor mode-locked lasers can be configured as multiwavelength pulse sources and are good candidates for time and wavelength division multiplexing applications. The gain medium in external cavity semiconductor mode-locked lasers is a semiconductor optical amplifier (SOA), and passive and hybrid mode-locked operation are achieved by the introduction of a saturable absorber (SA) in the laser cavity. Pump-probe techniques were used to measure the intracavity absorption dynamics of a SA in an external cavity semiconductor mode-locked laser and the gain dynamics of a SOA for the amplification of diverse pulses. The SOA gain dynamics measurements include the amplification of 750 fs pulses, 6.5 ps pulses, multiwavelength pulses and the intracavity gain dynamics of an external cavity multiwavelength semiconductor mode-locked laser. The experimental results show how the inherent chirp on pulses from external cavity semiconductor mode-locked lasers results in a slow gain depletion without significant fast gain dynamics. In the multiwavelength operation regime of these lasers, the chirp broadens the temporal pulse profile and decreases the temporal beating resulting from the phase correlation among wavelength channels. This results in a slow gain depletion mitigating nonlinearities and gain competition among wavelength channels in the SOA supporting the multiwavelength operation of the laser. Numerical simulations support the experimental results.
Show less - Date Issued
- 2006
- Identifier
- CFE0001359, ucf:46984
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001359
