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PHOTODISRUPTION IN OCULAR TISSUE NEAR AND AT THE BOUNDARY BETWEEN THE ANTERIOR CHAMBER AND CRYSTALLINE LENS
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.
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Date Issued
2011
Identifier
CFE0003658, ucf:48817
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003658
DEBRIS CHARACTERIZATION AND MITIGATION OF DROPLET LASER PLASMA SOURCES FOR EUV LITHOGRAPHY
Title
DEBRIS CHARACTERIZATION AND MITIGATION OF DROPLET LASER PLASMA SOURCES FOR EUV LITHOGRAPHY.
Creator
Takenoshita, Kazutoshi, Richardson, Martin, University of Central Florida
Abstract / Description
Extreme ultraviolet lithography (EUVL) is a next generation lithographic techniques under development for fabricating semiconductor devices with feature sizes smaller than 32 nm. The optics to be used in the EUVL steppers is reflective optics with multilayer mirror coatings on each surface. The wavelength of choice is 13.5 nm determined by the optimum reflectivity of the mirror coatings. The light source required for this wavelength is derived from a hot-dense plasma produced by either a gas...
Show moreExtreme ultraviolet lithography (EUVL) is a next generation lithographic techniques under development for fabricating semiconductor devices with feature sizes smaller than 32 nm. The optics to be used in the EUVL steppers is reflective optics with multilayer mirror coatings on each surface. The wavelength of choice is 13.5 nm determined by the optimum reflectivity of the mirror coatings. The light source required for this wavelength is derived from a hot-dense plasma produced by either a gas discharge or a laser. This study concentrate only on the laser produced plasma source because of its advantages of scalability to higher repetition rates. The design of a the laser plasma EUVL light source consists of a plasma produced from a high-intensity focused laser beam from a solid/liquid target, from which radiation is generated and collected by a large solid angle mirror or array of mirrors. The collector mirrors have the same reflectivity characteristics as the stepper mirrors. The EUVL light source is considered as the combination of both the hot-dense plasma and the collector mirrors. The EUVL light sources required by the stepper manufacturers must have sufficient EUV output power and long operational lifetimes to meet market-determined chip production rates. The most influential factor in achieving the required EUV output power is the conversion efficiency (CE) of laser input energy relative to the EUV radiation collected. A high CE is demonstrated in a separate research program by colleagues in the Laser Plasma laboratory at CREOL. Another important factor for the light source is the reflectivity lifetime of the collection optics as mirror reflectivity can be degraded by deposition and ablation from the plasma debris. Realization of a high CE but low debris plasma source is possible by reducing the mass of the target, which is accomplished by using tin-doped droplet targets. These have sufficient numbers of tin atoms for high CE, but the debris generation is minimal. The first part of this study investigates debris emissions from tin-doped droplet targets, in terms of aerosols and ions. Numerous tin aerosols can be created during a single laser-target interaction. The effects these interactions are observed and the depositions are investigated using SEM, AFM, AES, XPS, and RBS techniques. The generation of aerosols is found to be the result of incomplete ionization of the target material, corresponding to non-optimal laser coupling to the target for maximum CE. In order to determine the threats of the ion emission to the collector mirror coatings from an optimal, fully ionized target, the ion flux is measured at the mirror distance using various techniques. The ion kinetic energy distributions obtained for individual ion species are quantitatively analyzed. Incorporating these distributions with Monte-Carlo simulations provide lifetime estimation of the collector mirror under the effect of ion sputtering. The current estimated lifetime the tin-doped droplet plasma source is only a factor of 500 less than the stepper manufacturer requirements, without the use of any mitigation schemes to stop these ions interacting with the mirror. The second part of this investigation explores debris mitigation schemes. Two mitigation schemes are applied to tin-doped droplet laser plasmas; electrostatic field mitigation, and a combination of a foil trap with a magnetic field. Both mitigation schemes demonstrate their effectiveness in suppressing aerosols and ion flux. A very small number of high-energy ions still pass through the combination of the two mitigation schemes but the sputtering caused by these ions is too small to offer a threat to mirror lifetime. It is estimated that the lifetime of the collector mirror, and hence the source lifetime, will be sufficient when tin-doped targets are used in combination with these mitigation schemes.
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Date Issued
2006
Identifier
CFE0001289, ucf:46920
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001289
CONTROL AND STABILIZATION OF LASER PLASMASOURCES FOR EUV LITHOGRAPHY
Title
CONTROL AND STABILIZATION OF LASER PLASMASOURCES FOR EUV LITHOGRAPHY.
Creator
Cunado, Jose, Richardson, Martin, University of Central Florida
Abstract / Description
Extreme Ultraviolet (EUV) sources rely on droplet laser plasmas for EUV generation. These sources consist of a small (30 μm diameter) droplet which is excited into plasma emitting EUV around 13.5 nm, the industry's chosen wavelength for EUV lithography (EUVL). These sources are the best candidates for the commercialization of EUVL allowing mass production of computer chips with 32 nm or even smaller feature size. However, the biggest challenges which EUV source developers encounter...
Show moreExtreme Ultraviolet (EUV) sources rely on droplet laser plasmas for EUV generation. These sources consist of a small (30 μm diameter) droplet which is excited into plasma emitting EUV around 13.5 nm, the industry's chosen wavelength for EUV lithography (EUVL). These sources are the best candidates for the commercialization of EUVL allowing mass production of computer chips with 32 nm or even smaller feature size. However, the biggest challenges which EUV source developers encounter today are the issues of conversion efficiency (CE) and debris.In order to satisfy the technology requirements, the source will need to meet high levels of stability, performance, and lifetime. Our tin-doped droplet plasma has demonstrated high CE and low debris resulting in long lifetime. Long term stability is obtained through the use of novel tracking techniques and active feedback. The laser plasma targeting system combines optical illumination and imaging, droplet technology innovation, advanced electronics, and custom software which act in harmony to provide complete stabilization of the droplets. Thus, a stable, debris-free light source combined with suitable collection optics can provide useful EUV radiation power. Detailed description of the targeting system and the evaluation of the system will be presented.
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Date Issued
2007
Identifier
CFE0001790, ucf:47278
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001790
PLASMA TEMPERATURE MEASUREMENTS IN THE CONTEXT OF SPECTRAL INTERFERENCE
Title
PLASMA TEMPERATURE MEASUREMENTS IN THE CONTEXT OF SPECTRAL INTERFERENCE.
Creator
Seesahai, Brandon, Baudelet, Matthieu, University of Central Florida
Abstract / Description
The path explored in this thesis is testing a plasma temperature measurement approach that accounts for interference in a spectrum. The Atomic Emission Spectroscopy (AES) technique used is called Laser Induced Breakdown Spectroscopy (LIBS) and involves focusing a laser pulse to a high irradiance onto a sample to induced a plasma. Spectrally analyzing the plasma light provides a "finger print" or spectrum of the sample. Unfortunately, spectral line broadening is a type of interference...
Show moreThe path explored in this thesis is testing a plasma temperature measurement approach that accounts for interference in a spectrum. The Atomic Emission Spectroscopy (AES) technique used is called Laser Induced Breakdown Spectroscopy (LIBS) and involves focusing a laser pulse to a high irradiance onto a sample to induced a plasma. Spectrally analyzing the plasma light provides a "finger print" or spectrum of the sample. Unfortunately, spectral line broadening is a type of interference encountered in a LIBS spectrum because it blends possible ionic or atomic transitions that occur in plasma. To make use of the information or transitions not resolved in a LIBS spectrum, a plasma temperature method is developed. The basic theory of a LIBS plasma, broadening mechanisms, thermal equilibrium and distribution laws, and plasma temperature methods are discussed as background support for the plasma temperature method tested in this thesis. In summary, the plasma temperature method analyzes the Full Width at Half the Maximum (FWHM) of each spectral line for transitions provided from a database and uses them for temperature measurements. The first implementation of the temperature method was for simulated spectra and the results are compared to other conventional temperature measurement techniques. The temporal evolution of experimental spectra are also taken as a function of time to observe if the newly developed temperature technique can perform temporal measurements. Lastly, the temperature method is tested for a simulated, single element spectrum when considering interferences from all the elements provided in an atomic database. From stimulated and experimental spectra analysis to a global database consideration, the advantages and disadvantages of the temperature method are discussed.
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Date Issued
2016
Identifier
CFH2000140, ucf:46057
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH2000140
THE EFFECTS OF ELECTRODE GEOMETRY ON CURRENT PULSE CAUSED BY ELECTRICAL DISCHARGE OVER AN ULTRA-FAST LASER FILAMENT
Title
THE EFFECTS OF ELECTRODE GEOMETRY ON CURRENT PULSE CAUSED BY ELECTRICAL DISCHARGE OVER AN ULTRA-FAST LASER FILAMENT.
Creator
Bubelnik, Matthew, Siders, Craig, University of Central Florida
Abstract / Description
The time-resolved electrical conductivity of a short-pulse generated plasma filament in air was studied. Close-coupled metal electrodes were used to discharge the stored energy of a high-voltage capacitor and the resulting microsecond-scale electrical discharge was measured using fast current sensors. Significant differences in the time dependence of the current were seen with the two electrode geometries used. Using sharp-tipped electrodes additional peaks in the time-resolved conductivity...
Show moreThe time-resolved electrical conductivity of a short-pulse generated plasma filament in air was studied. Close-coupled metal electrodes were used to discharge the stored energy of a high-voltage capacitor and the resulting microsecond-scale electrical discharge was measured using fast current sensors. Significant differences in the time dependence of the current were seen with the two electrode geometries used. Using sharp-tipped electrodes additional peaks in the time-resolved conductivity were seen, relative to the single peak seen with spherical electrodes. We attribute these additional features to secondary electron collisional ionization brought about by field enhancement at the tips. Additional discrepancies in the currents measured leaving the high-voltage electrode and that returning to ground were also observed. Implications for potential laser-induced discharge applications will be discussed.
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Date Issued
2005
Identifier
CFE0000447, ucf:46378
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000447
RADIATION STUDIES OF THE TIN-DOPED MICROSCOPIC DROPLET LASER PLASMA LIGHT SOURCE SPECIFIC TO EUV LITHOGRAPHY
Title
RADIATION STUDIES OF THE TIN-DOPED MICROSCOPIC DROPLET LASER PLASMA LIGHT SOURCE SPECIFIC TO EUV LITHOGRAPHY.
Creator
Koay, Chiew-Seng, Richardson, Martin, University of Central Florida
Abstract / Description
Extreme ultraviolet lithography(EUVL) is being developed worldwide as the next generation technology to be inserted in ~ 2009 for the mass production of IC chips with feature sizes
Show moreExtreme ultraviolet lithography(EUVL) is being developed worldwide as the next generation technology to be inserted in ~ 2009 for the mass production of IC chips with feature sizes <35 nm. One major challenge to its implementation is the development of a 13.5 nm EUV source of radiation that meets the requirements of current roadmap designs of the source of illumination in commercial EUVL scanners. The light source must be debris-free, in a free-space environment with the imaging EUV optics that must provide sufficient, narrow spectral band EUV power to print 100 wafers/hr. To meet this need, extensive studies on emission from a laser plasma source utilizing tin-doped droplet target was conducted. Presented in this work, are the many optical techniques such as spectroscopy, radiometry, and imaging, that were employed to characterize and optimize emission from the laser plasma source State of the art EUV spectrographs were employed to observe the source's spectrum under various laser irradiation conditions. Comparing the experimental spectra to those from theory, has allowed the determination of the Sn ion stages responsible for emitting into the useful EUV bandwidth. Experimental results were compared to spectral simulations obtained using Collisional-Radiative Equilibrium (CRE) model, as well. Moreover, extensive measurements surveying source emission from 2 nm to 30 nm, which is the region of the electromagnetic spectrum defined as EUV, was accomplished. Absolutely calibrated metrology was employed with the Flying Circus instrument from which the source's conversion efficiency (CE)--from laser to the useful EUV energy--was characterized under various laser irradiation conditions. Hydrodynamic simulations of the plasma expansion together with the CRE model predicted the condition at which optimum conversion could be attained. The condition was demonstrated experimentally, with the highest CE to be slightly above 2%, which is the highest value among all EUV source contenders. In addition to laser intensity, the CE was found to depend on the laser wavelength. For better understanding, this observation is compared to results from simulations. Through a novel approach in imaging, the size of the plasma was characterized by recording images of the plasma within a narrow band, around 13.5 nm. The size, approximately 100 ìm, is safely within the etendue limit set by the optical elements in the EUV scanner. Finally, the notion of irradiating the target with multiple laser beams was explored for the possibility of improving the source's conversion efficiency.
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Date Issued
2006
Identifier
CFE0000938, ucf:46733
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000938
LASER PLASMA RADIATION STUDIES FOR DROPLET SOURCES IN THE EXTREME ULTRAVIOLET
Title
LASER PLASMA RADIATION STUDIES FOR DROPLET SOURCES IN THE EXTREME ULTRAVIOLET.
Creator
Kamtaprasad, Reuvani, Richardson, Martin, University of Central Florida
Abstract / Description
The advancement of laboratory based Extreme Ultraviolet (EUV) radiation has escalated with the desire to use EUV as a source for semiconductor device printing. Laser plasmas based on a mass-limited target concept, developed within the Laser Plasma Laboratory demonstrate a much needed versatility for satisfying rigorous source requirements. This concept produces minimal debris concerns and allows for the attainment of high repetition rates as well as the accommodation of various laser and...
Show moreThe advancement of laboratory based Extreme Ultraviolet (EUV) radiation has escalated with the desire to use EUV as a source for semiconductor device printing. Laser plasmas based on a mass-limited target concept, developed within the Laser Plasma Laboratory demonstrate a much needed versatility for satisfying rigorous source requirements. This concept produces minimal debris concerns and allows for the attainment of high repetition rates as well as the accommodation of various laser and target configurations. This work demonstrates the generation of EUV radiation by creating laser plasmas from mass-limited targets with indium, tin, and antimony doped droplets. Spectral emission from the laser plasmas is quantified using a flat-field spectrometer. COWAN code oscillator strength predications for each of the dopants were convolved with narrow Gaussian functions creating synthetic spectra for the EUV region between 10 nm - 20 nm. A preliminary comparison was made between the theoretical spectra and experimental results. From this comparison, ion stage transitions for each of the hot dense plasmas generated were assessed.
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Date Issued
2010
Identifier
CFE0003168, ucf:48597
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003168
Plasma Dynamics of Laser Filaments
Title
Plasma Dynamics of Laser Filaments.
Creator
Reyes, Danielle, Richardson, Martin, Gaume, Romain, Chini, Michael, University of Central Florida
Abstract / Description
Laser filamentation is a complex phenomenon occurring for pulses with peak power above a critical value. A filament is a dynamic self-guided structure characterized by several unique qualities, which include a beam with a high-intensity core surrounded by an energy reservoir, a weakly ionized plasma channel, and supercontinuum generation. Several of the proposed applications for filamentation utilize the plasma channel, such as for assisted electric discharge and microwave guiding. However,...
Show moreLaser filamentation is a complex phenomenon occurring for pulses with peak power above a critical value. A filament is a dynamic self-guided structure characterized by several unique qualities, which include a beam with a high-intensity core surrounded by an energy reservoir, a weakly ionized plasma channel, and supercontinuum generation. Several of the proposed applications for filamentation utilize the plasma channel, such as for assisted electric discharge and microwave guiding. However, filament properties are highly influenced by the physical conditions under which they are formed. A host of studies have been conducted to further characterize filaments, but much work still remains in order to understand their complex behavior. This work presents an accurate and direct measurement of the electron density based on an interferometric technique. The impact of different initial parameters on filament spatio-temporal dynamics in air is investigated, concentrating primarily on their influence on the plasma. For comparison of the experiment with theory, the plasma decay is modeled by a system of kinetic equations that takes into account three-body and dissociative electron recombination reactions.
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Date Issued
2017
Identifier
CFE0006646, ucf:51222
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006646
Development of laser spectroscopy for elemental and molecular analysis
Title
Development of laser spectroscopy for elemental and molecular analysis.
Creator
Liu, Yuan, Richardson, Martin, Vanstryland, Eric, Bass, Michael, Sigman, Michael, University of Central Florida
Abstract / Description
Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are still growing analytical and sensing spectroscopic techniques. They significantly reduce the time and labor cost in analysis with simplified instrumentation, and lead to minimal or no sample damage. In this dissertation, fundamental studies to improve LIBS analytical performance were performed and its fusion with Raman into one single sensor was explored.On the fundamental side, Thomson scattering was reported for the...
Show moreLaser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are still growing analytical and sensing spectroscopic techniques. They significantly reduce the time and labor cost in analysis with simplified instrumentation, and lead to minimal or no sample damage. In this dissertation, fundamental studies to improve LIBS analytical performance were performed and its fusion with Raman into one single sensor was explored.On the fundamental side, Thomson scattering was reported for the first time to simultaneously measure the electron density and temperature of laser plasmas from a solid aluminum target at atmospheric pressure. Comparison between electron and excitation temperatures brought insights into the verification of local thermodynamic equilibrium condition in laser plasmas.To enhance LIBS emission, Microwave-Assisted LIBS (MA-LIBS) was developed and characterized. In MA-LIBS, a microwave field extends the emission lifetime of the plasma and stronger time integrated signal is obtained. Experimental results showed sensitivity improvement (more than 20-fold) and extension of the analytical range (down to a few tens of ppm) for the detection of copper traces in soil samples. Finally, laser spectroscopy systems that can perform both LIBS and Raman analysis were developed. Such systems provide two types of complimentary information (-) elemental composition from LIBS and structural information from Raman. Two novel approaches were reported for the first time for LIBS-Raman sensor fusion: (i) an Ultra-Violet system which combines Resonant Raman signal enhancement and high ablation efficiency from UV radiation, and (ii) a Ti:Sapphire laser based NIR system which reduces the fluorescence interference in Raman and takes advantage of femtosecond ablation for LIBS.
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Date Issued
2013
Identifier
CFE0005105, ucf:50729
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005105
Enhanced Ablation by Femtosecond and Nanoseond Laser Pulses
Title
Enhanced Ablation by Femtosecond and Nanoseond Laser Pulses.
Creator
Kerrigan, Haley, Richardson, Martin, Baudelet, Matthieu, Shivamoggi, Bhimsen, University of Central Florida
Abstract / Description
Laser ablation of GaAs by a combination of femtosecond and nanosecond pulses is investigated as a means of enhancing material removal by a femtosecond pulse in the filamentation intensity regime. We demonstrate for the first time increased ablation of GaAs by ultrafast laser pulse plasmas augmented by nanosecond pulse radiation from a secondary laser. Material removal during laser ablation is a complex process that occurs via multiple mechanisms over several timescales. Due to different pulse...
Show moreLaser ablation of GaAs by a combination of femtosecond and nanosecond pulses is investigated as a means of enhancing material removal by a femtosecond pulse in the filamentation intensity regime. We demonstrate for the first time increased ablation of GaAs by ultrafast laser pulse plasmas augmented by nanosecond pulse radiation from a secondary laser. Material removal during laser ablation is a complex process that occurs via multiple mechanisms over several timescales. Due to different pulse durations, ablation by femtosecond and nanosecond pulses are dominated by different mechanisms. Ablation can be enhanced by optimally combining a femtosecond and nanosecond pulse in time. In this work, the craters generated by combinations of pulses are investigated for inter-pulse delays ranging from -50ns to +1?s, with the fs pulse preceding the ns pulse corresponding to a positive delay. The Ti:Sapph Multi-Terawatt Femtosecond Laser (MTFL) in the Laser Plasma Laboratory (LPL) provides 50fs pulses at 800nm with intensities of 1014W/cm^2 at the sample. An Nd:YAG laser (Quantel CFR200) provides 8ns pulses at 1064nm with intensities of 109W/cm^2. Crater profilometry with white-light interferometry and optical microscopy determine the structure and surface features of the craters and the volume of material removed. Ultrafast shadowgraphy of the ejected plasma provides insight to the dual-pulse ablation dynamics. Sedov-Taylor analysis of the generated shockwave reveals the energy coupled to the sample or preceding plasma. It was found that inter-pulse delays between +40 and +200ns yielded craters 2.5x greater in volume than that of the femtosecond pulse alone, with a maximum enhancement of 2.7x at +100ns. Shadowgraphy of -40 to +40ns delays revealed that enhancement occurs when the nanosecond pulse couples to plasma generated by the fs pulse. This work provides a possible means of enhancing ablation by femtosecond filaments, which propagate long distances with clamped intensity, advancing long-range stand-off ablation
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Date Issued
2017
Identifier
CFE0006889, ucf:51734
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006889
LASER INDUCED BREAKDOWN SPECTROSCOPY FOR DETECTION OF ORGANIC RESIDUES: IMPACT OF AMBIENT ATMOSPHERE AND LASER PARAMETERS
Title
LASER INDUCED BREAKDOWN SPECTROSCOPY FOR DETECTION OF ORGANIC RESIDUES: IMPACT OF AMBIENT ATMOSPHERE AND LASER PARAMETERS.
Creator
Brown, Christopher, Richardson, Martin, University of Central Florida
Abstract / Description
Laser Induced Breakdown Spectroscopy (LIBS) is showing great potential as an atomic analytical technique. With its ability to rapidly analyze all forms of matter, with little-to-no sample preparation, LIBS has many advantages over conventional atomic emission spectroscopy techniques. With the maturation of the technologies that make LIBS possible, there has been a growing movement to implement LIBS in portable analyzers for field applications. In particular, LIBS has long been considered the...
Show moreLaser Induced Breakdown Spectroscopy (LIBS) is showing great potential as an atomic analytical technique. With its ability to rapidly analyze all forms of matter, with little-to-no sample preparation, LIBS has many advantages over conventional atomic emission spectroscopy techniques. With the maturation of the technologies that make LIBS possible, there has been a growing movement to implement LIBS in portable analyzers for field applications. In particular, LIBS has long been considered the front-runner in the drive for stand-off detection of trace deposits of explosives. Thus there is a need for a better understanding of the relevant processes that are responsible for the LIBS signature and their relationships to the different system parameters that are helping to improve LIBS as a sensing technology. This study explores the use of LIBS as a method to detect random trace amounts of specific organic materials deposited on organic or non-metallic surfaces. This requirement forces the limitation of single-shot signal analysis. This study is both experimental and theoretical, with a sizeable component addressing data analysis using principal components analysis to reduce the dimensionality of the data, and quadratic discriminant analysis to classify the data. In addition, the alternative approach of 'target factor analysis' was employed to improve detection of organic residues on organic substrates. Finally, a new method of characterizing the laser-induced plasma of organics, which should lead to improved data collection and analysis, is introduced. The comparison between modeled and experimental measurements of plasma temperatures and electronic density is discussed in order to improve the present models of low-temperature laser induced plasmas.
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Date Issued
2011
Identifier
CFE0003708, ucf:48843
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003708
SPECTROSCOPIC STUDIES OF LASER PLASMAS FOR EUV SOURCES
Title
SPECTROSCOPIC STUDIES OF LASER PLASMAS FOR EUV SOURCES.
Creator
George, Simi, Richardson, Martin, University of Central Florida
Abstract / Description
With the availability of high reflectivity multilayer mirrors and zone plate lenses, the EUV region (5nm - 40nm) of the electromagnetic spectrum is currently being explored for applications of nanoscale printing and imaging. Advances made in this area have consequences for many areas of science. Research for producing a compact, bright EUV source for laboratory use has gained momentum in recent years. For this study, EUV radiation is produced by irradiating target materials using a focused...
Show moreWith the availability of high reflectivity multilayer mirrors and zone plate lenses, the EUV region (5nm - 40nm) of the electromagnetic spectrum is currently being explored for applications of nanoscale printing and imaging. Advances made in this area have consequences for many areas of science. Research for producing a compact, bright EUV source for laboratory use has gained momentum in recent years. For this study, EUV radiation is produced by irradiating target materials using a focused laser beam. Focused laser beam ionizes the target to create a hot, dense, pulsed plasma source, where emission is a result of the relaxation of excited levels. Spectroscopy is used as the main diagnostic to obtain the spectral signature of the plasma. Spectral characteristics are used to deduce the physical state of plasma, thus enabling the tuning of laser irradiance conditions to maximize the needed emission bandwidth. Various target materials are studied, as well as different target geometries, with spectroscopy below 200 nm on pulsed micro-plasmas being a particularly daunting task. Total range spectroscopy from 1 nm to greater than 1 micron is completed for tin-doped spherical droplet plasma source. Reliable plasma diagnostics require both accurate measurements and solid theoretical support in order to interpret the experimental results. Using existing 1D-hydrocode, temperature and density characteristics of the expanding plasma is simulated for any set of experimental conditions. Existing atomic codes written for calculating one-electron radial wavefunctions with LS-coupling scheme via Hartree-Fock method is used in order to gain details of the ion stages, populations, transitions, etc, contributing to the spectral data.
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Date Issued
2007
Identifier
CFE0001972, ucf:47433
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001972
EXTREME ULTRAVIOLET SPECTRAL STREAK CAMERA
Title
EXTREME ULTRAVIOLET SPECTRAL STREAK CAMERA.
Creator
Szilagyi, John, Richardson, Martin, University of Central Florida
Abstract / Description
The recent development of extreme ultraviolet (EUV) sources has increased the need for diagnostic tools, and has opened up a previously limited portion of the spectrum. With ultrafast laser systems and spectroscopy moving into shorter timescales and wavelengths, the need for nanosecond scale imaging of EUV is increasing. EUVÂÂÂÂ's high absorption has limited the number of imaging options due...
Show moreThe recent development of extreme ultraviolet (EUV) sources has increased the need for diagnostic tools, and has opened up a previously limited portion of the spectrum. With ultrafast laser systems and spectroscopy moving into shorter timescales and wavelengths, the need for nanosecond scale imaging of EUV is increasing. EUVÂÂÂÂ's high absorption has limited the number of imaging options due to the many atomic resonances in this spectrum. Currently EUV is imaged with photodiodes and X-ray CCDs. However photodiodes are limited in that they can only resolve intensity with respect to time and X-ray CCDs are limited to temporal resolution in the microsecond range. This work shows a novel approach to imaging EUV light over a nanosecond time scale, by using an EUV scintillator to convert EUV to visible light imaged by a conventional streak camera. A laser produced plasma, using a mass-limited tin based target, provided EUV light which was imaged by a grazing incidence flat field spectrometer onto a Ce:YAG scintillator. The EUV spectrum (5 nm-20 nm) provided by the spectrometer is filter by a zirconium filter and then converted by the scintillator to visible light (550 nm) which can then be imaged with conventional optics. Visible light was imaged by an electron image tube based streak camera. The streak camera converts the visible light image to an electron image using a photocathode, and sweeps the image across a recording medium. The streak camera also provides amplification and gating of the image by the means of a micro channel plate, within the image tube, to compensate for low EUV intensities. The system provides 42 ns streaked images of light with a temporal resolution of 440 ps at a repetition rate of 1 Hz. Upon calibration the EUV streak camera developed in this work will be used in future EUV development.
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Date Issued
2010
Identifier
CFE0003558, ucf:48905
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003558
Precision Metrology of Laser Plasmas in the XUV Band
Title
Precision Metrology of Laser Plasmas in the XUV Band.
Creator
Szilagyi, John, Richardson, Martin, Sundaram, Kalpathy, Abdolvand, Reza, Baudelet, Matthieu, Shivamoggi, Bhimsen, University of Central Florida
Abstract / Description
The XUV band, a region of light spanning the wavelength range of 5 - 200 nm, is located between the Ultraviolet and X-ray regions of the electromagnetic spectrum. It is further divided into a 100 - 200 nm region called the Vacuum Ultraviolet (VUV), and a 5 (-) 100 nm region called the Extreme Ultraviolet (EUV). Applications of this light have been slow to develop due to the lack of suitable sources, efficient optics, and sensitive detectors. Recently, many industries such as the semiconductor...
Show moreThe XUV band, a region of light spanning the wavelength range of 5 - 200 nm, is located between the Ultraviolet and X-ray regions of the electromagnetic spectrum. It is further divided into a 100 - 200 nm region called the Vacuum Ultraviolet (VUV), and a 5 (-) 100 nm region called the Extreme Ultraviolet (EUV). Applications of this light have been slow to develop due to the lack of suitable sources, efficient optics, and sensitive detectors. Recently, many industries such as the semiconductor manufacturing industry, medical surgery, micromachining, microscopy, and spectroscopy have begun to benefit from the short wavelengths and the high photon energies of this light. At present, the semiconductor chip industry is the primary reason for the investment in, and development of, XUV sources, optics, and detectors. The demand for high power EUV light sources at 13.5 nm wavelength is driven by the development of the next generation of semiconductor lithography tools. The development of these tools enables the continued reduction in size, and the increase in transistor density of semiconductor devices on a single chip. Further development and investigation of laser produced plasma EUV light sources is necessary to increase the average optical power and reliability. This will lead to an increase in the speed of EUV lithographic processes, which are necessary for future generations of advanced chip design, and high volume semiconductor manufacturing. Micromachining, lithography, and microscopy benefit from improvements in resolution due to the shorter wavelengths of light in the VUV band. In order to provide adequate illumination for these applications, sources are required which are brighter and have higher average power. Laser produced plasma (LPP) VUV light sources are used extensively for lithography and defect detection in semiconductor manufacturing. Reductions in the wavelength and increases in the average power will increase the rate and yield of chip manufacture, as well as reduce the costs of semiconductor manufacture.The work presented in this thesis, describes the development of two laser plasma source facilities in the Laser Plasma Laboratory at UCF, which were designed to investigate EUV and VUV laser plasma sources. The HP-EUV-Facility was developed to optimize and demonstrate a high power 13.5 nm EUV LPP source. This facility provides high resolution spectroscopy across 10.5 - 20 nm, and absolute energy measurement of 13.5 nm +/- 2% in 2? sr. The VUV-MS-Facility was developed to investigate VUV emission characteristics of laser plasmas of various target geometries and chemistries. This facility provides absolute calibrated emission spectra for the 124 - 250 nm wavelength range, in addition to, at wavelength plasma imaging. Calibrated emission spectra, in-band power, and conversion efficiency are presented in this work for gas targets of Argon, Krypton, and Xenon and solid targets of Silicon, Copper, Molybdenum, Indium, Tantalum, Tin, and Zinc, across the laser intensity range of 8.0x10^6 (-) 3.2x10^12 W/cm2.
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Date Issued
2017
Identifier
CFE0006805, ucf:51793
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006805
Engineering and Application of Ultrafast Laser Pulses and Filamentation in Air
Title
Engineering and Application of Ultrafast Laser Pulses and Filamentation in Air.
Creator
Barbieri, Nicholas, Richardson, Martin, University of Central Florida
Abstract / Description
Continuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter.The need to better...
Show moreContinuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter.The need to better control the light obtained from increasingly advanced laser sources leads to the emergence of beam engineering, the systematic understanding and control of light through refractive media and free space. Beam engineering enables control over the beam shape, energy and spectral composition during propagation, which can be achieved through a variety of means. In this dissertation, several methods of beam engineering are investigated. These methods enable improved control over the shape and propagation of laser light. Laser-matter interaction is also investigated, as it provides both a means to control the propagation of pulsed laser light through the atmosphere, and provides a means to generation remote sources of radiation.
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Date Issued
2013
Identifier
CFE0004650, ucf:49881
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004650