8 research outputs found

    Laser Systems for Applications

    Get PDF
    This book addresses topics related to various laser systems intended for the applications in science and various industries. Some of them are very recent achievements in laser physics (e.g. laser pulse cleaning), while others face their renaissance in industrial applications (e.g. CO2 lasers). This book has been divided into four different sections: (1) Laser and terahertz sources, (2) Laser beam manipulation, (3) Intense pulse propagation phenomena, and (4) Metrology. The book addresses such topics like: Q-switching, mode-locking, various laser systems, terahertz source driven by lasers, micro-lasers, fiber lasers, pulse and beam shaping techniques, pulse contrast metrology, and improvement techniques. This book is a great starting point for newcomers to laser physics

    High-power femtosecond laser-oscillators for applications in high-field physics

    Get PDF
    In dieser Doktorarbeit werden experimentelle Anstrengungen zur Entwicklung eines kompakten Laseroszillators für Femtosekundenimpulse mit hoher Durchschnitts- und Spitzenleistung beschrieben. Dabei zielt dieser Laser auf neuartige Anwendung in der Spektroskopie und Hochfeldphysik ab, insbesondere dem Antreiben von ineffizienten Frequenzkonversionsprozessen wie der Erzeugung von mittlerer Infrarot- und extrem ultravioletter Strahlung. Die entwickelten Strahlquellen bestehen dabei aus einem kerrlinsenmodengekoppelten Hochleistungsscheibenlaser auf Basis von Yb:YAG mit mehreren MHz Wiederholrate und einer anschließenden Impulskompressionsstufe aus massiven Festkörpern. Es wird aufgezeigt, dass Kerrlinsenmodenkopplung sowohl durchschnitts-, als auch spitzenleistungsskalierbar ist und die derzeit einzige Methode zur Modenkopplung, die simultan die effiziente Ausbeute der gesamten Verstärkungsbandbreite des Verstärkungsmediums zulässt. Impulse mit mehr als 60 MW Spitzenleistung und hunderten Watt an Durchschnittsleistung können direkt am Oszillatorausgang erreicht werden mit Impulslängen bis hinab zu 140 fs. Der Hochleistungsoutput des Oszillators wurde in massiven Festkörpermaterialien spektral verbreitert, um die Durchführbarkeit eines effizienten, kompakten und robusten Impulskompressors auszuloten, der sich nicht auf justageempfindliche Fasern verlassen muss. Gestützt durch frühere Arbeiten, sowie neue Experimente, als auch Simulationen konnte festgestellt werden, dass die Nachahmung eines nichtlinearen Quasiwellenleiters zu außerordentlich hoher Effizienz im Durchsatz führen und dabei herausragende Komprimierbarkeit über dem gesamten Strahl sicherstellen kann. Die Impulse mit 60 MW Spitzen- und 150 W Durchschnittsleistung aus einem der entwickelten Oszillatoren wurden in einem sehr kompakten Quasiwellenleiter spektral verbreitert und anschließend mit gechirpten Spiegeln auf 30 fs komprimiert. Durch die hohe Transmission des gesamten Aufbaus von 95 % wurde die Spitzenleistung auf 230 MW hochgetrieben. Simulationen zeigen die Umsetzbarkeit eines Kompressors auf Basis dieser Wellenleiter mit Pulsdauern, die mit 10 fs bis in den Bereich weniger optischer Schwingungszyklen hineinreichen. Untersucht wurde ebenfalls ein anderer Ansatz zur spektralen Verbreiterung, der auf kaskadierten χ(2) Nichtlinearitäten während der Erzeugung der zweiten Harmonischen in BBO mit fehlangepasster Phase beruht. Obgleich die Effizienz nicht vergleichbar mit der des Wellenleiteransatzes ist, machen ihn die faszinierende Möglichkeit zu defokussierenden Phasenschüben und Selbstkompression im Kristall zu einem interessanten Ausgangspunkt für sehr kompakte Impulskompressionsaufbauten. Das Zusammenspiel dieser Entwicklungen zeigt die Realisierbarkeit von unverstärkten, einfachen und kompakten Laserquellen auf, die komplexere und preisintensive Yb- oder Ti:Safir Verstärkersysteme ersetzen können.This thesis describes experimental work in the development of a compact, high average and peak-power femtosecond oscillator. This laser targets new applications in spectroscopy and high-field physics, especially the driving of inefficient frequency-conversion-processes like the generation of mid-infrared and extreme ultraviolet radiation. The developed sources consist of a high-power Kerr-lens mode-locked Yb:YAG thin-disk oscillator with multi-MHz repetition rate and a subsequent all-bulk pulse-compression stage. It is shown that Kerr-lens mode-locking is both average and peak-power scalable and is currently the only mode-locking technique that at the same time allows the efficient use of the full gain-bandwidth of the amplifying medium. Pulses with more than 60 MW peak-power and hundreds of watts in average power can be reached as direct oscillator output with down to 140 fs pulse-duration. The high-power output from the oscillators was spectrally broadened in bulk solids to explore the feasibility of an efficient, compact and robust pulse-compressor that does not have to rely on alignment-sensitive fibers. Leaning on previous work as well as new experiments and computer simulations it was found that the emulation of a nonlinear quasi-waveguide can yield exceptionally high throughput efficiency, while retaining excellent whole-beam compressibility. The 60 MW peak- and 150 W average power pulses from a developed oscillator were spectrally broadened in a very compact quasi-waveguide and subsequently compressed with chirped mirrors to 30 fs pulse duration. By virtue of the 95 % transmission of the whole setup the peak-power was boosted to 230 MW. Simulations show the feasibility of a waveguide based compressor with down to 10 fs pulse duration into the few-optical-cycle regime. A different approach to spectral broadening, relying on cascaded χ(2) nonlinearities from phase-mismatched second-harmonic generation in BBO was also investigated. Although the efficiency is not comparable to the waveguide approach, the intriguing possibility of defocusing phase-shifts and self-compression in the crystal make it an interesting starting point for very compact pulse-compression setups. The combination of these developments demonstrates the feasibility of non-amplified, simple and compact laser sources that can replace more complex and costly Yb or Ti:Sapphire amplifier systems

    Mode-locked Pulses in Passive Coherent Beam Combining Fiber Laser Arrays.

    Full text link
    This thesis presents the first dynamic model for the simultaneous coherent combining and mode locking of fiber lasers. The model shows very good agreement with experiment and suggests a novel approach to producing high-peak-power pulse trains with tunable repetition rates in excess of a gigahertz for potential applications to optical clocking, telecommunications, and ultrafast optics. Passive coherent beam combining relies on the use of evanescent coupling between individual lasers to create a phased array in order to scale up the output power and brightness of fiber lasers. Mode locking, on the other hand, is a method of generating short pulses with high peak power by coherently phasing all the longitudinal modes of a single laser. Our work combines the two techniques in a model based on the amplifying Nonlinear Schrödinger Equation (NLSE) for each fiber laser, a fast saturable absorber equation for mode locking, and a directional coupler matrix for combining the individual lasers. The coupling between individual lasers of different length leads to the formation of array modes created from the subset of longitudinal modes that are common to all the fibers. As the common longitudinal modes, the array modes naturally lead to a frequency comb with a tooth separation much greater than that of the single-cavity longitudinal modes. Locking of these modes by a saturable absorber results in a pulse train whose repetition rate, given by the array mode separation, is inversely proportional to the fiber length difference and is thus tunable. Our model has been applied to both Erbium-doped fiber lasers operating in a wavelength region of anomalous dispersion (1.5 microns) and to Ytterbium-doped fiber lasers operating at 1.06 microns where the dispersion is normal. In the normal dispersion regime we find that the combination of saturable absorption and spectral filtering results in highly chirped dissipative solitons that contain more energy than those created in the anomalous dispersion region. The dissertation concludes with a novel analysis of the optical tunneling process that underlies the operation of the directional couplers used in beam combining. The analysis explains some paradoxical phenomena that had hitherto been interpreted as superluminal propagation.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102469/1/chaozh_1.pd

    Theory of nonlinear and amplified surface plasmon polaritons

    Get PDF
    This thesis presents a study of Surface Plasmon Polaritons (SPPs) in hybrid metal-dielectric waveguides. The embedding of metal in nanostructured photonic components allows for manipulating and guiding light at the subwavelength scale. Such an extreme confinement enhances the nonlinear response of the dielectric medium, which is important for applications in optical processing of information, but is paid in terms of considerable ohmic loss in the metal. It is, however, possible to embed externally pumped active inclusions in the dielectric in order to compensate for the metal loss. A novel perturbative theory for Maxwell equations is introduced and applied to various nonlinear metal-dielectric structures, deriving the propagation equation for the optical field. The nonlinear dispersion law for amplified SPPs, filamentation and dissipative plasmon-soliton formation have been studied, revealing intrinsic core and tail instabilities that prevent solitons to propagate over long distances. Stable propagation of plasmon-solitons can be achieved in insulator-metal-insulator structures with active and passive interfaces. The active SPP is coupled with the passive SPP, which absorbs the perturbations destabilising the zero background of the soliton. Theoretical modelling of optical propagation in metal-dielectric stacks predicts a modified two-band structure, allowing for gap/discrete plasmon-soliton formation. Loss and nonlinear parameters in subwavelength nanowire waveguides are evaluated and compared to the results obtained by other research groups. In all calculations, particular attention is paid in considering boundary conditions accounting for loss and nonlinear corrections, which contribute to the propagation equation with a surface term that becomes significant in the subwavelength regime.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Optical Communication

    Get PDF
    Optical communication is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters cover general concepts of optical communication, components, systems, networks, signal processing and MIMO systems. In recent years, optical components and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on optical devices, networking, signal processing, and MIMO systems and other enhanced functions for optical communication. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries

    Laboratory Directed Research and Development FY 1998 Progress Report

    Full text link
    corecore