To see the other types of publications on this topic, follow the link: Laser Seeker.
Dissertations / Theses on the topic 'Laser Seeker'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 25 dissertations / theses for your research on the topic 'Laser Seeker.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hubbard, Keith, Gary Katulka, Dave Lyon, Doug Petrick, Frank Fresconi, and T. G. Horwath. "Low-Cost Semi-Active Laser Seekers for US Army Application." International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606162.
Full textAbstract:
ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaThe U.S. Army Research Laboratory (ARL) is exploring technologies to provide low-cost precision fires, applicable across both direct and indirect fire weapon systems. One of these applications involves a forward observer (FO) designating the target with a laser spot and a seeker on-board the munition detecting the reflected energy to allow terminal guidance. This approach, referred to as semi-active laser (SAL) guidance, has been utilized on numerous air-delivered munitions to include bombs, missiles and projectiles. However, the cost of these systems, driven by high quality optics, high sensitivity detectors and specialized electronics, has hampered their migration into gun-fired munitions such as mortars, artillery and grenades. To explore, develop and demonstrate minimal cost solutions, ARL invested in an Army Technical Objective (ATO) called Smaller, Lighter, Cheaper Munition Components (SLCMC). Specifically, SAL seeker hardware, predicated upon commercial components (COTS) and mass production techniques, is being prototyped for use with gun launched projectiles and laser target designators. The seeker system is comprised of several printed circuit board boards, a microprocessor, a quad-photo detector and, a molded optical lens unit. This seeker is designed to rapidly update the projectile boresight angle, interface with other strap-down sensors, and feed data into an on-board guidance, navigation & control (G,N&C) system to allow for projectile maneuvers. The seeker design and basic characteristics are discussed and presented through-out the paper and presentation.
2
Akkal, Elzem. "Control Actuation Systems And Seeker Units Of An Air-to-surface Guided Munition." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1028430/index.pdf.
Full textAbstract:
This thesis proposes a modification to an air to surface guided munition (ASGM) from bang-bang control scheme to continuous control scheme with a little cost. In this respect, time domain system identification analysis is applied to the control actuation system (CAS) of ASGM in order to obtain its mathematical model and controller is designed using pulse width modulation technique. With this modification, canards would be deflected as much as it is commanded to. Seeker signals are also post-processed to obtain the angle between the velocity vector and target line of sight vector. The seeker is modeled using an artificial neural network. Non-linear flight simulation model is built using MATLAB Simulink and obtained seeker and CAS models are integrated to the whole flight simulation model having 6 degrees of freedom. As a flight control unit, fuzzy logic controller is designed, which is a suitable choice if an inertial measurement sensor will not be mounted on the munition. Finally, simulation studies are carried out in order to compare the performance of the &ldquoASGM&rdquo
and &ldquo
improved ASGM&rdquo
and the superiority of the new design is demonstrated.
3
Guner, Dunya Rauf Levent. "Modeling Of A Generic Laser Guided Weapon With Velocity Pursuit Guidance And Its Performance Analysis Using Various Control Strategies." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605386/index.pdf.
Full textAbstract:
In this thesis, a base for the modeling and analysis of laser guided weapons is constituted. In particular, the effects of several control schemes on the performance of a generic laser guided weapon system are investigated. In this generic model, it is assumed that the velocity pursuit guidance is employed via a velocity aligning seeker as the sole sensor.
The laser seeker is modeled experimentally, based on data obtained by conducting a series of tests. The laser reflection is also modeled. Aerodynamic coefficients of the generic geometry are generated by the software Missile Datcom. A nonlinear, six degree of freedom simulation is constructed incorporating 10 Hz laser sensing, velocity pursuit guidance, seeker model, and multiple control schemes.
The effects of bang-bang, bang-trail-bang, multiposition and continuous control techniques on weapon performance are investigated for stationary and moving targets under ideal and noisy conditions. Flight characteristics like miss distance, range envelope, impact speed, and time of flight are monitored. Weapon’
s maneuverability is investigated and the effect of employing a theoretical down sensor on the performance is demonstrated. In the light of simulation results, comparisons between various schemes are carried out, improvements on them and their flight envelopes are emphasized. It is concluded that the multiposition scheme provides a significant performance increase in most delivery types and can be an alternative to the continuous scheme. It is shown that the continuous scheme can achieve longer ranges only if backed up by a down sensor.
4
McDaniel, Sean A. "Seeded, Gain-switched Chromium Doped Zinc Selenide Amplifier." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1343760359.
Full text
5
Maroju, Praveen Kumar [Verfasser], and Giuseppe [Akademischer Betreuer] Sansone. "Attosecond pulse shaping at a seeded free-electron laser : : towards attosecond time-resolved experiments at the free-electron lasers." Freiburg : Universität, 2021. http://d-nb.info/1239556527/34.
Full text
6
Labat, M., M. Hosaka, M. Shimada, M. Katoh, and M. E. Couprie. "Optimization of a Seeded Free-Electron Laser with Helical Undulators." American Physical Society, 2008. http://hdl.handle.net/2237/11342.
Full text
7
Willis-Ott, Christina. "Ytterbium-doped fiber-seeded thin-disk master oscillator power amplifier laser system." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5890.
Full textAbstract:
Lasers which operate at both high average power and energy are in demand for a wide range of applications such as materials processing, directed energy and EUV generation. Presented in this dissertation is a high-power 1 ?m ytterbium-based hybrid laser system with temporally tailored pulse shaping capability and up to 62 mJ pulses, with the expectation the system can scale to higher pulse energies. This hybrid system consists of a low power fiber seed and pre-amplifier, and a solid state thin-disk regenerative amplifier. This system has been designed to generate high power temporally tailored pulses on the nanosecond time scale. Temporal tailoring and spectral control are performed in the low power fiber portion of the system with the high pulse energy being generated in the regenerative amplifier. The seed system consists of a 1030 nm fiber-coupled diode, which is transmitted through a Mach-Zehnder-type modulator in order to temporally vary the pulse shape. Typical pulses are 20-30 ns in duration and have energies of ~0.2 nJ from the modulator. These are amplified in a fiber pre-amplifier stage to ~100 nJ before being used to seed the free-space Yb:YAG thin-disk regenerative amplifier. Output pulses have maximum demonstrated pulse energies of 62 mJ with 20 ns pulse after ~250 passes in the cavity. The effects of thermal distortion in laser and passive optical materials are also. Generally the development of high power and high energy lasers is limited by thermal management strategies, as thermally-induced distortions can degrade laser performance and potentially cause catastrophic damage. Novel materials, such as optical ceramics, can be used to mitigate thermal distortions; however, thorough analysis is required to optimize their fabrication and minimize thermal distortions. Using a Shack-Hartmann wavefront sensor (SHWFS), it is possible to analyze the distortion induced in passive and doped optical elements by high power lasers. For example, the thin-disk used in the regenerative amplifier is examined in-situ during CW operation (up to 2 kW CW pump power). Additionally, passive oxide-based optical materials and Yb:YAG optical ceramics are also examined by pumping at 2 and 1 ?m respectively to induce thermal distortions which are analyzed with the SHWFS. This method has been developed as a diagnostic for the relative assessment of material quality, and to grade differences in ceramic laser materials associated with differences in manufacturing processes and/or the presence of impurities. In summation, this dissertation presents a high energy 1 ?m laser system which is novel in its combination of energy level and temporal tailoring, and an analysis of thermal distortions relevant to the development of high power laser systems.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
8
Eriksson, Mirjam. "Tunable diode laser absorptionspectroscopy of atomic potassium in a KOH-seeded flat flame." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-146503.
Full textAbstract:
Potassium (K) is the main ash-forming element released from biomass during thermochemical conversion. A better understanding of K chemistry and monitoring of K species is needed to optimize combustion systems. Since K species are highly reactive and prevailing concentrations depend on the conversion conditions, accurate quantification requires in situ measurement techniques. Tunable diode laser absorption spectroscopy with a single-mode distributed feedback laser is used to probe the D1 transition of atomic potassium, K(g), at 769.9 nm. The large current tuning range of the diode laser (5 cm-1) enables monitoringthe wings of the absorption profile. Fitting to the acquired line shape wings is used as astrategy to enhance the dynamic range of the sensor and measure K(g) concentrations even under optically thick condition. A potassium-rich combustion environment is simulated by converting KOH salt in a premixed methane/air flat flame. Quantitative measurements of K(g) are made at 75 positions in the flame. This yields radial K(g) profiles at three different heightsin the plume above the KOH salt and an axial profile at the burner center. The acquired average K(g) concentrations are corrected for effective plume size, i.e. the absorption pathlength determined from the radial profiles. Knowledge of the K(g) distribution in flames can lead to a better understanding of K release and primary reaction kinetics.
9
Fahlenkamp, Keith B. "Direct observation of two phase flow generated by an alumina seeded grain in high aspect ratio channels." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Jun/10Jun%5FFahlenkamp.pdf.
Full textAbstract:
Thesis (Mechanical Engineer and M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2010.Thesis Advisor(s): Brophy, Christopher ; Second Reader: Gannon, Anthony. "June 2010." Description based on title screen as viewed on July 13, 2010. Author(s) subject terms: Solid rocket propellant, two phase flow, erosive burning, alumina agglomeration, laser imaging Includes bibliographical references (p. 87). Also available in print.
10
Twumasi, Ricardo. "Working late : exploring the new dynamics of later life working in light of changes in age related legislation, policy and practice." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/21765.
Full textAbstract:
Demographic changes have facilitated longer, healthier lives, and legislative changes have encouraged extended working lives through the increasing of state pension age, equalisation of state pensions, and the removal of the default retirement age. Recent age discrimination legislation has begun to combat age discrimination within the employment context of the UK. Legal precedent has also been established during the course of this research through case law, as a result of high profile age discrimination cases reaching the Supreme Court. Through several interview studies, this thesis explores the experiences, views and attitudes of employees, employers, job seekers and retired individuals. Utilising focus groups, this thesis also presents data from a range of charity representatives, human resources professionals, line managers, employment advisors, health and safety practitioners, and trade union representatives in order to explore the influence of changes in later life working policy and practice. The research of this thesis also includes a consultation exercise to engage the potential users of the research and develops a policy and practice framework providing recommendations which could lead to better outcomes and improved opportunities for older workers. Finally, a series of video case studies presents the research findings in an accessible visual format. This varied use of communication methods was specifically selected in order to increase the impact of the research and potential user audience. Research findings highlighted that managing age diversity was perceived as essential for employee motivation and organisational competitiveness. In particular, interviewees from generationally diverse workforces also reported a more positive attitude to age. Evidence from this thesis presents direct examples of age discrimination limiting the employment opportunities of older workers. Potential victims of age discrimination often struggle to gather evidence to support their perception that they may have been mistreated due to their age. Especially for job seekers, the perception of age discrimination presents a significant barrier to confidence, motivation, and opportunities during the employment search. These concerns are also exacerbated by the most widely reported barrier to securing employment for older jobseekers which was insufficient feedback. While a small minority of employers discussed discriminatory practices, the majority were positive towards age diversity and embraced the benefits of older workers. Responsibility for retirement transitions and performance management as older employees reach the end of their careers were issues employers reported struggling with in light of the removal of the default retirement age. The findings of this thesis highlight the importance of challenging age stereotypes and embracing the opportunities that a multi-generational workforce offers in order to increase equality of opportunity and promote age positive organisational culture. All parts of society have a shared responsibility to change attitudes towards older workers, and offer workers of all ages the equality they deserve.
11
Plath, Tim [Verfasser], and Jörg [Akademischer Betreuer] Rossbach. "Measurements and Detailed Analysis of Seeded High-Gain Free-Electron Lasers at FLASH / Tim Plath ; Betreuer: Jörg Rossbach." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/1141904993/34.
Full text
12
Samulski, Camille Clement. "Deceleration Stage Rayleigh-Taylor Instability Growth in Inertial Confinement Fusion Relevant Configurations." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/103703.
Full textAbstract:
Experimental results and simulations of imploding fusion concepts have identified the Rayleigh-Taylor (RT) instability as one of the largest inhibitors to achieving fusion. Understanding the origin and development of the RT instability will allow for the development of mitigating measures to dampen the instability growth, thus improving the chance that fusion concepts such as inertial confinement fusion (ICF) are successful. A study of 1D and 2D simulations are presented for investigating RT instability growth in deceleration stage of imploding geometries. Two cases of laser-driven implosion geometry, Cartesian and cylindrical, are used to study late stage deceleration-phase RT instability development on the interior surface of imploding targets. FLASH's hydrodynamic (HD) and magnetohydrodynamic (MHD) modeling capabilities are used for different laser and target parameters in order to study the RT instability and the impact of externally applied magnetic fields on their evolution. Several simulation regimes have been identified that provide novel insight into the impact that a seeded magnetic field can have on RT instability growth and the conditions under which magnetic field stabilization of the RT instability is observable. Finally, future work and recommendations are made.Master of Science
The direction for the future of renewable energy is uncertain at this time; however, it is known that the future of human energy consumption must be green in order to be sustainable. Fusion energy presents an opportunity for an unlimited clean renewable energy source that has yet to be realized. Fusion is achieved only by overcoming the earthly limitations presented by trying to replicate conditions at the interior of stellar structures. The pressures, temperature, and densities seen in the interior of stars are not easily reproduced, and thus human technology must be developed to reach these difficult stellar conditions in order to harvest fusion energy. There are two main branches of developmental technology geared towards achieving the difficult conditions controlled nuclear fusion presents, magnetic confinement fusion (MCF) and inertial confinement fusion (ICF)[17]. Yet in both approaches barriers exist which have thwarted the efforts toward reaching fusion ignition which must be addressed through scientific discovery. Successfully reaching ignition is only the first step in the ultimate pursuit of a self sustaining fusion reactor. This work will focus on the experimental ICF configuration, and on one such inhibitor toward achieving ignition, the Rayleigh-Taylor (RT) instability. The RT instability develops on the surfaces of the fusion fuel capsules, targets, and causes nonuniform compression of the target. This nonuniform compression of the target leads to lower pressures and densities through the material mixing of fusion fuel and the capsule shell, which ultimately leads to challenges with reaching fusion ignition. The work presented here was performed utilizing the University of Chicago's FLASH code, which is a state-of-the-art open source radiation magneto-hydrodynamic (MHD) code used for plasma and astrophysics computational modeling [11]. Simulations of the RT instability are performed using FLASH in planar and cylindrical geometries to explore fundamental Rayleigh-Taylor instability evolution for these two different geometries. These geometries provide easier access for experimental diagnostics to probe RT dynamics. Additionally, the impact of externally applied magnetic fields are explored in an effort to examine if and how the detrimental instability can be controlled.
13
Eilenberger, Stefanie [Verfasser], and Christian [Akademischer Betreuer] Hagl. "The effect of TAVI-simulation and perfusion on the cell layer of decellularized and re-seeded homografts / Stefanie Eilenberger ; Betreuer: Christian Hagl." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1206096381/34.
Full text
14
Oliva, Eduardo. "Amélioration d'un code hydrodynamique avec transport der ayonnement et maillage avec raffinement adaptatif (AMR) et son application aux lasers X." Palaiseau, Ecole polytechnique, 2010. http://pastel.archives-ouvertes.fr/docs/00/55/93/53/PDF/Oliva.pdf.
Full textAbstract:
L'injection d'harmoniques dans des amplificateurs gazeux génère des faisceaux de rayonnement X de grand qualité. Puisque les amplificateurs basés sur cible solide sont plus denses que ceux générés sur cible gazeuse, des impulsions d'énergie supérieure et plus courtes sont attendue. Cependant, les expériences réalisées n'ont pas présenté d'énergies supérieures à 90 nJ et des durées inférieures à 1 ps. Dans cette thèse nous nous sommes concentrés sur le problème de la différence entre l'énergie extraite et celle prédite, avec pour objectif d'obtenir des faisceaux de quelques dizaines de microjoules par impulsion. Nous avons employé le code ARWEN, déjà utilisé dans ce domaine, et l'avons amélioré dans le cadre de cette thèse. Les travaux réalisés sont donc : - L'étude théorique des sources de rayonnement X cohérent, en insistant sur les sources basées sur plasmas. L'état de l'art et la physique de ces amplificateurs sont décrits en profondeur. - La description du code ARWEN et des améliorations introduites dans le cadre de cette thèse. Ainsi que les programmes utilisés pour le postprocess des donnés. - L'optimisation des amplificateurs au moyen de simulations numériques. Ces simulations continuent les travaux précédentes et expliquent les effets donnant lieu aux différences entre l'énergie obtenue expérimentalement et celle prédite théoriquement. En prenant en compte ces effets, nous proposons un amplificateur optimisé. Nous avons aussi étudié l'amplification du faisceau harmonique en concluant au besoin d'un pré-amplificateur. En résumé, nous avons amélioré le code ARWEN en ajoutant de nouvelles capacités de simulation et l'avons utilisé pour étudier la physique des amplificateurs de rayonnement X cohérent basés sur plasmas. L'évolution de ces plasmas a été comprise et nous a permis d'expliquer les différences entre les expériences et la théorie et proposer un moyen de réduire les pertes d'énergieSeeding experiments achieved with gas amplifiers demonstrated high quality X ray beams. Since amplifiers based on solid targets are denser than those generated from gas, higher energy and shorter pulse durations were expected. However, experiments demonstrated lower energy around 90 nJ and slightly shorter pulse duration down to 1 ps. We concentrated this thesis on the understanding of the mismatch between expected and measured energies for solid targets with the goal to find a way for producing seeded plasma-based soft x-ray laser emitting tens of microjoules per pulse as required by many applications. This work has been done with the code ARWEN. This code had already been used in this field but it has been improved in the frame of this thesis, adding new computational capabilities. The work presented in this thesis is: - Theoretical study of coherent X-ray sources, emphasizing the plasma-based sources. The state of the art and the physics of these amplifiers are described more thoroughly. - Description of the ARWEN code, the fundamental tool of this work, and the improvements introduced in it (ray tracing, parallelization of thermal conduction subroutines, standard HDF output, etc. . . ). In addition to this, the codes used for prostprocessing the data are also described. - Optimization of plasma amplifiers by means of numerical models. These studies start from previous works, continuing the work and explaining the effects that lead to the differences between the predicted energy and the energy experimentally observed. Some ways to avoid these effects are proposed. An study of the amplification of the injected seed in these plasmas is also presented, concluding that pre-amplifier stages are essential. Thus, nowadays a code with new simulation capabilities (ARWEN)is available and it can be applied to several fields (not only plasma-based soft X-ray lasers). It has been used to study plasma-based amplifiers, gaining an insight into the physics of these systems, explaining the differences between experimental results and theoretical predictions. In addition to this, it has been proposed a new scheme to optimize these amplifiers
15
Kelly, Kurtis. "Laser ionization and radiofrequency sustainment of high-pressure seeded plasmas." 2001. http://www.library.wisc.edu/databases/connect/dissertations.html.
Full text
16
Chen, Sung-Nan, and 陳松楠. "A Novel MEMS-based External Cavity Self-Seeded Tunable Semiconductor Laser." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/98488562532432920762.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
92
With the progressively technological development in small forms, and its associated miniaturization specification in fiber-optic communication as well as the increasing demand in transmission capacity with low cost scheme, the miniaturized tunable laser is being driven to become an increasing role of active sources, which is able to provide multiple functions with a small-form configuration. In this study, leveraging MEMS technology in device miniaturization, and thus in small-form configuration of a whole system, the tunable laser based on a MEMS-based external cavity of wavelength-selective self-seeding mechanism leads to miniaturization in a small-form requirement. The miniaturized external-cavity tunable laser is significant in simplified components in system level, single- and dual-wavelength output, and independent wavelength ON/OFF tuning. In this study, the MEMS-based external-cavity tunable laser system is comprised of a simple and inexpensive Fabry-Perot laser diode as a light source, a bulk grating for wavelength dispersion in free space, and an addressable micro corner mirror array for wavelength selection and switching. Among those components in this optical system to be the most critical is the corner mirror that requires nearly perfect verticality for reflection to be fed back into the laser diode. The corner mirror requires two orthogonal planes that include in-plane mirror and vertical mirror. The in-plane mirror that serves as the top electrode is freely tortional across a certain gap to its bottom electrode underneath. Therefore, with the voltage application across these electrodes, the in-plane mirror is able to be electrostatically attracted down onto the bottom electrode substrate so as to no longer maintain its orthogonal form for reflection lasing. In addition, the micro corner mirror array placed in a lightpath of first-order diffraction of the optical system is addressable for wavelength selection in free space. The resultant selected wavelength was then reflectively fed back to its original source as a seeding wavelength for resonance in overall output. Of particular interest is its verticality of micro corner mirrors that determines reflection back into its laser diode in a long travel of external cavity. The deviation out of its right angle was measured to be approximate 0.015o. In this MEMS-based wavelength-tunable external-cavity diode laser, the single mode side mode suppression ratio was measured to be up to 15 dB. Furthermore, by maintaining two distant micro corner mirrors in “ON” state in which four in-plane mirrors in between those two were torsionally driven down, the dual wavelength output in 1532.2 nm and 1540.1 nm simultaneously were accomplished. At last, the micro corner mirrors has proven to be successfully used in wavelength selection as well as wavelength switching in the external-cavity wavelength tunable diode laser.
17
Jou, Heng-sheng, and 周恆生. "Tunable self-seeded and gain-switched laser diode with spersion compensation." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/91388463421891663503.
Full textAbstract:
碩士國立交通大學
光電(科學)研究所
83
In this thesis, we describe the construnction and the characterzation of a wavelength-tunable gain-switched laser diode with intra-cavity dispersion compensation. The system consists of a commerical high-power laser diode (1.3um), and a folded dispersive delay line consisting of a grazing incidence diffration grating, and a lens, a strip mirror and a translat- able lens-strip mirror assembly. In continuous wave (cw) operation, the tuning range of the laser is 26nm with a side- mode suppression ratio better than 30dB. In self-seeded and gain-switched operation, we have generated 9.1ps pulses with wavelength tunability of 25nm. The side-mode suppression ratio is about 30dB. This novel laser system should be very useful for a number of applications.
18
Chi, Lang-Chung, and 紀嵐中. "Frequency-stabilization of Tunable Self-seeded-dual-wavelength Semiconductor Lasers." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/31681327751694799062.
Full text
19
Nelson, Brent. "The Development of a Frequency Control System of a Seeded Laser for DGV Application." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-181.
Full textAbstract:
For an effective Doppler Global Velocimeter (DGV), there is a requirement to
accurately record and tune the frequency content of the laser used. The laser used for
this experiment was an ND:YAG. Adjusting the mean frequency of the ND:YAG is
accomplished by controlling the seed laser diode output, which also narrows the
bandwidth of the laser to below 20 MHz. The exact frequency of operation is critical for
the operation of the system. Standard interferometry techniques that measure laser
frequency content, such as Fabre-Perot and grating based systems, are not able to
provide an adequate spectrum resolution for the 9 ns pulse duration of the ND:YAG
laser. A method was developed that employs a CCD line camera and a laser reference
cell to effectively and cost efficiently solve this problem. The hardware and software for
this real time monitoring system were developed and used with a real time feedback loop
to stabilize the laser operating frequency at a specified value. The receiving optics of
this DGV system were upgraded with 12 bit CCD cameras and a temperature controlled
laser reference cell to decrease the uncertainty to the velocity measurement from over 4 m/s to less than 1 m/s. Recommendations to the effectiveness of the system and future
improvements are provided.
20
Shian, Miin-liang, and 蕭敏良. "Measurement of velocity distributionof seeded jet beams by laser-induced fluorescence and imaging techniques." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/55381760113190122072.
Full text
21
Huang, Chin-Hao, and 黃金豪. "Master Oscillator of Fiber Power Amplifier Seeded by Nd:YVO4/Cr4+:YAG Passively Q-Switched Laser." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/23406166527188827346.
Full textAbstract:
碩士國立交通大學
理學院應用科技學程
99
We report on an analysis of the design guideline of a hemispherical resonator Nd:YVO4/Cr4+:YAG passively Q-Switched (PQS) laser by optimization of the mode matching condition and agreement with the good PQS criterion. Cr4+:YAG saturable absorbers with various initial transmission were used to investigate the performances of the laser configuration. Then we inject these high-peak-power PQS laser to realize the single-stage, linear-polarized fiber amplifier. With the seed laser of pulse repetition rate (PRR) of 50 kHz, the amplifier emits pulse energy of 178 and peak power of 37 kW under the pump power of 16 W. With the seed laser of PRR of 25 kHz, we can attain the amplifier with pulse energy of 192 and peak power of 113 kW under the pump power of 10 W which is restricted by the fiber facet damage.
22
Lin, Ping-Hsun, and 林秉勳. "Development of Multi-Line and Seeded Waveguide-Based Soft X-Ray Lasers." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/90175180648187653164.
Full textAbstract:
博士臺灣大學
物理研究所
98
It has been nearly half a century since the invention of lasers, the use of coherent light has become an indispensable part of our world, such as optical communications, precision measurements, optical memories, and medicine. Rapid progress in technology has led to the development of coherent lights that operate in short-wavelength regions, examples of such light sources include soft x-ray lasers. The use of soft x-ray lasers has considerable potential from the viewpoint of pioneering research in various scientific fields like high-resolution microscopy and holography, dense plasma measurement, and nano-lithography; visible lasers are inadequate for these purposes. With the advent of high-power short-pulse lasers, especially the high-repetition-rate terawatt lasers based on the chirped-pulse amplification technique, it is now possible to generate ultrashort coherent soft x-rays with a much lower cost and small size. An ultrashort high-intensity laser pulse combined with the optical-field-ionization (OFI) collisional-excitation mechanism can be used to produce a suitable x-ray gain medium: highly ionized plasma. In addition, the ultrashort feature of the pumping source can overcome the problem of the short duration of the gain in the x-ray region. Considering the size and cost, the use of a table-top, high brightness, soft x-ray laser is advantageous as compared to synchrotron radiations or x-ray free electron lasers. This thesis first reports the development of an OFI collisional-excitation soft x-ray laser that uses an optically preformed plasma waveguide. Using a 9-mm-long pure krypton plasma waveguide prepared by the axicon ignitor-heater scheme, Ni-like Kr lasing at a wavelength of 32.8 nm can be enhanced by 400 times relative to the case without the plasma waveguide. An output level of 8×10^10 photons/pulse can be obtained at an energy conversion efficiency of 2×10^6. Then, under the same configuration of the pump and waveguide-forming pulses, strong Pd-like xenon lasing and Ne-like argon lasing were realized at wavelengths of 41.8 nm and 46.9 nm, respectively. In addition to the main lasing lines for Ni-like krypton and Ne-like argon, other lasing lines are also observed; this is indicative of a strong enhancement effect and a large gas density in the plasma waveguide. With a Kr/Ar mixed gas multi-species parallel x-ray lasing was also demonstrated, showing the capability of generating multi-line soft x-ray lasers by using the optically preformed plasma waveguide. In order to gain a better understanding of waveguide-based soft x-ray lasers and control them suitably, extensive experimental results on the pump-energy dependence, density dependence, and effects of parameters that control the waveguide fabrication were studied in detail. Finally, in order to realize further improvements in the optical qualities of the soft x-ray laser, a strongly saturated waveguide-based OFI soft-x-ray laser seeded by high harmonic generation (HHG) was demonstrated for Ni-like Kr lasing at a wavelength of 32.8 nm. HHG is produced from the nonlinear interaction between intense laser and gas atoms. During this process, electrons that are ionized from the gas atoms oscillate with the laser field; subsequently, they recombine with their parent ions and emit high-energy photons. The emissions from di®erent atoms add constructively and thus retain good spatial and temporal coherence. As compared to laser seeded with only spontaneous emission, the divergence of seeding with HHG is greatly reduced from 4.5 mrad to 1.1 mrad, which is about the same as that of the HHG seed. The amplified HHG seed pulse also shows enhanced spatial coherence and controlled polarization. Moreover, seeded x-ray lasers do not suffer from timing jitter relative to the pump laser; this is important for pump-probe applications. We believe that the integration of high-harmonic seeding, optically preformed plasma waveguide, and OFI pumping forms one of the optimal archetype of a high-repetition-rate, high-intensity, ultrashort-pulse soft x-ray laser.
23
Chen, Yi-Chun, and 陳怡君. "Theory and Experiment of a Full-field Wave Propagation Metrology System: Developing a Dynamic ESPI and Holographic Recording/Playback System by Using an Injection-seeded Twin-cavity Pulse Laser." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/07931997097887661351.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
88
The elastic wave propagation and mechanical vibration measurements are important issues in the mechanics field. Optical measurement has long been one of the most important tasks in the non-destructive testing related applications due to its non-contact and high-resolution characteristics. An innovative time-resolved full-field dynamic wave propagation metrology system was designed during this research work. The wave propagation analysis can be achieved by measuring the time sequence of an object dynamic deformation. An injection-seeded double-pulsed Nd:YAG laser that is capable of emitting two coherent orthogonally-polarized laser pulses was integrated with an ultra-high precision piezoelectric impact hammer to create a double-object dual-reference holographic and electronic speckle pattern interferometry system. Phase shifting technology, direct correlation method, and path-independent phase unwrapping methodology were introduced to measure full-field ultrahigh-speed transient surface motions with approximately 2 nm resolution in height. The experimental data obtained in the ESPI-setup verified the effectiveness of our newly developed system.
24
Ren, Yi Ting, and 任頤庭. "Generation of High-Power Sub-picosecond Pulses by Chirped-Pulse Amplification Technique Based on a Dual-Stage Yitterbium-Doped Polarization Maintaining Fiber Amplifier Seeded by Picosecond All-Normal Dispersion Yb-Fiber Laser." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/28841344985011992788.
Full textAbstract:
碩士國立清華大學
物理系
104
In the thesis, we studied the chirped pulse amplification (CPA) system based on a dual-stage Yb-doped polarization-maintaining (PM) fibers seeded with a picosecond-scale all-normal dispersion (ANDi) fiber laser with pulse duration of 15 ps and average output power of 50 mW. The dual-stage amplifier was composed of 7-m-long 10-μm Yb-doped PM fiber and 5-m-long 30-μm Yb-doped PM fiber as a pre-amplifier and a main amplifier, respectively. In the experiment, due to strong nonlinearities induced by PM fibers and third order dispersion (TOD) of the fiber stretcher, we could not obtain sub-picosecond pulses in CPA system. But the power efficiency was raised up to about 50% for the characteristic of PM fibers in maintaining polarization of pulses so that the power would not loss due to the selection of polarization in grating compressor. Under the condition of the best compensation in SOD and TOD, the highest peak power of the compressed pulse was ~90 kW with pulse duration of 1.7 ps in FWHM and 1.94 ps in EA definition and the pulse energy was 174 nJ with 65% pulse energy concentration which was improved up to 35% comparing to normal-fiber-based CPA system.
25
Borysow, Michael. "A high-intensity cold atom source." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6249.
Full textAbstract:
Presented in this thesis is the design and characterization of a new, high-flux source of cold atoms based on continuous, post-nozzle injection of lithium atoms into a cryogenic, supersonic helium jet. To date, experiments have been performed with lithium injection fractions up to [approximately equal to]10⁻⁶, where fluorescence spectroscopy reveals successful capture and thermalization of lithium atoms within the helium jet. The observed lithium beam copropagates with the helium jet and has a temperature of less than 10 mK, a brightness of 1.1x10¹⁹ m⁻² s⁻¹ sr⁻¹, and a brilliance of 3.1x10²⁰ m⁻² s⁻¹ sr⁻¹. Lithium atoms contained within a solid angle of [approximately equal to]0.018 sr are good candidates for future magnetic extraction. This results in a potentially capturable lithium flux of 1.1x10¹² s⁻¹, comparable to the existing record for a cold atomic beam. Also presented is preliminary data showing lithium fluorescence nearly 1 m downstream, demonstrating that the cold lithium beam can be successfully extracted from the seeding region. Numerical simulations reproduce capture efficiency to within 50%, suggesting that the process is well understood. We believe that successful seeding may be possible at a fraction up to 10⁻⁴. Seeding at this rate could produce an atomic beam with a flux as high as 1.3x10¹⁴ s⁻¹ at a phase-space density up to 1.6x10⁻⁷, corresponding to brightness and brilliance of order 10²² m⁻² s⁻¹ sr⁻¹ and 10²⁴ m⁻² s⁻¹ sr⁻¹ , respectively. If this novel cooling method performs as well at higher incident lithium flux, it could serve as a pump source and pave the way to the realization of the first truly continuous atom laser.text