Development of optical parametric chirped-pulse amplifiers and their applications

In this work, optical pulse amplification by parametric chirped-pulse amplification (OPCPA) has been applied to the generation of high-energy, few-cycle optical pulses in the near-infrared (NIR) and infrared (IR) spectral regions. Amplification of such pulses is ordinarily difficult to achieve by existing techniques of pulse amplification based on standard laser gain media followed by external compression. Potential applications of few-cycle pulses in the IR have also been demonstrated. The NIR OPCPA system produces 0.5-terawatt (10 fs, 5 mJ) pulses by use of noncollinearly phase-matched optical parametric amplification and a down-chirping stretcher and upchirping compressor pair. An IR OPCPA system was also developed which produces 20-gigawatt (20 fs, 350 uJ pulses at 2.1 um. The IR seed pulse is generated by optical rectification of a broadband pulse and therefore it exhibits a self-stabilized carrier-envelope phase (CEP). In the IR OPCPA a common laser source is used to generate the pump and seed resulting in an inherent sub-picosecond optical synchronization between the two pulses. This was achieved by use of a custom-built Nd:YLF picosecond pump pulse amplifier that is directly seeded with optical pulses from a custom-built ultrabroadband Ti:sapphire oscillator. Synchronization between the pump and seed pulses is critical for efficient and stable amplification. Two spectroscopic applications which utilize these unique sources have been demonstrated. First, the visible supercontinuum was generated in a solid-state media by the infrared optical pulses and through which the carrier-envelope phase (CEP) of the driving pulse was measured with an f-to-3f interferometer. This measurement confirms the self-stabilization mechanism of the CEP in a difference frequency generation process and the preservation of the CEP during optical parametric amplification. Second, high-order harmonics with energies extending beyond 200 eV were generated with the few-cycle infrared pulses in an argon target. Because of the longer carrier period, the IR pulses transfer more quiver energy to ionized free electrons compared to conventional NIR pulses. Therefore, higher energy radiation is emitted upon recombination of the accelerated electrons. This result shows the highest photon energy generated by a laser excitation in neutral argon

High-Power Laser Systems for Driving and Probing High Energy Density Physics Experiments

This thesis describes the construction of a hybrid OPCPA and Nd:Glass based laser system to provide advanced diagnostic capabilities for the MAGPIE pulsed power facility at Imperial College London. The laser system (named Cerberus) is designed to provide one short pulse 500 fs beam for proton probing and two long pulse beams, one for x-ray backlighting and one for Thomson scattering. The aim of this project is to accurately determine plasma parameters in a range of demanding experimental environments. The thesis is split into two sections; the first section provides details about the design and implementation of the laser system while the latter chapters present experimental data obtained on the MAGPIE facilty. The front end for the laser system is based on optically synchronised Optical Parametric Chirped Puled Amplification (OPCPA) which is supplemented by large aperture flashlamp pumped Nd:Glass power amplifiers in the latter stages to increase the energy to the Joule level. The use of optical parametric amplifiers (OPAs) in the pre-amplifier stages reduces gain narrowing, B-integral and improves contrast. Simulations of the dispersive optics for the Chirped Pulse Amplification (CPA) system are described in detail. Spatially resolved Thomson scattering was used to measure temperature and velocity of ablation streams in aluminium and tungsten cylindrical wire arrays. The measurements show a peak ow velocity of 120 km/s and agree well with 3D MHD simulations for the case of aluminium. There is discrepancy with the tungsten data caused by the difficulty in handling of collisionality calculations. Novel data showing the self-emission of ions from tungsten radial wire arrays is presented as a key step towards laser driven proton probing of MAGPIE. It is observed that the bulk of the emission corresponds to low energy protons with energies of ~ 100 keV. Protons with energy > 600 keV were observed to emanate from the collapsing magnetic jet using a coded aperture camera. These results offer interesting new prospects in diagnosing wire arrays.Open Acces

Laser-induced forward transfer (LIFT) of water soluble polyvinyl alcohol (PVA) polymers for use as support material for 3D-printed structures

The additive microfabrication method of laser-induced forward transfer (LIFT) permits the creation of functional microstructures with feature sizes down to below a micrometre [1]. Compared to other additive manufacturing techniques, LIFT can be used to deposit a broad range of materials in a contactless fashion. LIFT features the possibility of building out of plane features, but is currently limited to 2D or 2½D structures [2–4]. That is because printing of 3D structures requires sophisticated printing strategies, such as mechanical support structures and post-processing, as the material to be printed is in the liquid phase. Therefore, we propose the use of water-soluble materials as a support (and sacrificial) material, which can be easily removed after printing, by submerging the printed structure in water, without exposing the sample to more aggressive solvents or sintering treatments. Here, we present studies on LIFT printing of polyvinyl alcohol (PVA) polymer thin films via a picosecond pulsed laser source. Glass carriers are coated with a solution of PVA (donor) and brought into proximity to a receiver substrate (glass, silicon) once dried. Focussing of a laser pulse with a beam radius of 2 µm at the interface of carrier and donor leads to the ejection of a small volume of PVA that is being deposited on a receiver substrate. The effect of laser pulse fluence , donor film thickness and receiver material on the morphology (shape and size) of the deposits are studied. Adhesion of the deposits on the receiver is verified via deposition on various receiver materials and via a tape test. The solubility of PVA after laser irradiation is confirmed via dissolution in de-ionised water. In our study, the feasibility of the concept of printing PVA with the help of LIFT is demonstrated. The transfer process maintains the ability of water solubility of the deposits allowing the use as support material in LIFT printing of complex 3D structures. Future studies will investigate the compatibility (i.e. adhesion) of PVA with relevant donor materials, such as metals and functional polymers. References: [1] A. Piqué and P. Serra (2018) Laser Printing of Functional Materials. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. [2] R. C. Y. Auyeung, H. Kim, A. J. Birnbaum, M. Zalalutdinov, S. A. Mathews, and A. Piqué (2009) Laser decal transfer of freestanding microcantilevers and microbridges, Appl. Phys. A, vol. 97, no. 3, pp. 513–519. [3] C. W. Visser, R. Pohl, C. Sun, G.-W. Römer, B. Huis in ‘t Veld, and D. Lohse (2015) Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer, Adv. Mater., vol. 27, no. 27, pp. 4087–4092. [4] J. Luo et al. (2017) Printing Functional 3D Microdevices by Laser-Induced Forward Transfer, Small, vol. 13, no. 9, p. 1602553

Laser Systems for Applications

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

Biophotonic applications of ultrafast fiber lasers: from biomaterial surface modification to sub-cellular nanosurgery

Ankara : The Department of Materials Science and Nanotechnology and the Graduate School of Engineering and Science of Bilkent University, 2014.Thesis (Ph. D.) -- Bilkent University, 2014.Includes bibliographical references leaves laaves 71-83.Just a year after the invention of the LASER in 1960, it was demonstrated that lasers could be used for the treatment of certain skin abnormalities. At present, lasers are extensively used in a broad range of medical treatments. After the development of femtosecond pulse lasers in the 1980s, even more exciting possibilities in a diverse range of fields have been realized. Accordingly, ultrashort pulse lasers are widely used in biological applications in recent years. In parallel to these, fiber laser systems have increasingly been utilized in a wide range of scientific and biomedical applications, since they are highly compatible systems for being employed for industrial and biomedical applications. Consequently, the aim of this Ph.D. thesis proposal is to develop compact, simpler to operate, and cost-efficient ultrafast fiber lasers with different repetition rates and pulse energies. By using such systems, we demonstrate the biophotonic applications of these lasers on two different biological research fields. As a part of this thesis study, we develop ultrafast fiber lasers and apply them in biomaterial surface modification. We demonstrate that different surfaces with micro- and nano-scale topographies can be generated at high speed, precision and repeatability. The outcomes of biomaterial surface modification with different laser parameters are compared in terms of topographical uniformity and repeatability. Additionally, a variety of topographical modifications are assessed with respect to the efficiency on cell attachment and proliferation on metal implants.As the second part of this thesis, we develop a custom-built ultrafast fiber laser-integrated microscope system for nanosurgery and tissue ablation experiments. Subsequently, we employ this system in order to make high-precision cuts onto different biological specimens ranging from the tissue level to subcellular level, such as a part of an axon or a single organelle. Finally, we improve this integrated system in a way that it becomes capable of generating optical pulses in any desired sequence possible. This is achieved by using acousto-optic modulators (AOM) and custom-developed field-programmable gate arrays (FPGA).Erdoğan, MutluPh.D

Technical Design Report EuroGammaS proposal for the ELI-NP Gamma beam System

The machine described in this document is an advanced Source of up to 20 MeV Gamma Rays based on Compton back-scattering, i.e. collision of an intense high power laser beam and a high brightness electron beam with maximum kinetic energy of about 720 MeV. Fully equipped with collimation and characterization systems, in order to generate, form and fully measure the physical characteristics of the produced Gamma Ray beam. The quality, i.e. phase space density, of the two colliding beams will be such that the emitted Gamma ray beam is characterized by energy tunability, spectral density, bandwidth, polarization, divergence and brilliance compatible with the requested performances of the ELI-NP user facility, to be built in Romania as the Nuclear Physics oriented Pillar of the European Extreme Light Infrastructure. This document illustrates the Technical Design finally produced by the EuroGammaS Collaboration, after a thorough investigation of the machine expected performances within the constraints imposed by the ELI-NP tender for the Gamma Beam System (ELI-NP-GBS), in terms of available budget, deadlines for machine completion and performance achievement, compatibility with lay-out and characteristics of the planned civil engineering

A time-based approach for multi-GHz embedded mixed-signal characterization and measurement /

The increasingly more sophisticated systems that are nowadays implemented on a single chip are placing stringent requirements on the test industry. New test strategies, equipment, and methodologies need to be developed to sustain the constant increase in demand for consumer and communication electronics. Techniques for built-in-self-test (BIST) and design-for-test (DFT) strategies have been proven to offer more feasible and economical testing solutions.Previous works have been conducted to perform on-chip testing, characterization, and measurement of signals and components. The current thesis advances those techniques on many levels. In terms of performance, an increase of more than an order of magnitude in speed is achieved. 70-GHz (effective sampling) on-chip oscilloscope is reported, compared to 4-GHz and 10-GHz ones in previous state-of-the-art implementations. Power dissipation is another area where the proposed work offer a superior solution compared to previous alternatives. All the proposed circuits do not exceed a few milliWatts of power dissipation, while performing multi-GHz high-speed signal capture at a medium resolution. Finally, and possibly most importantly, all the proposed circuits for test rely on a different form of signal processing; the time-based approach. It is believed that this approach paves the path to a lot of new techniques and circuit design skills that can be investigated more deeply. As an integral part of the time-based processing approach for GHz signal capture, this thesis verifies the advantages of using time amplification. The use of such amplification in the time domain is materialized with experimental results from three specific integrated circuits achieving different tasks in GHz high-speed in-situ signal measurement and characterization. Advantages of using such time-based approach techniques, when combined with the use of a front-end time amplifier, include noise immunity, the use of synthesizable digital cells, and circuit building blocks that track the technology scaling in terms of area and speed

A trillion frames per second: the techniques and applications of light-in-flight photography

Cameras capable of capturing videos at a trillion frames per second allow to freeze light in motion, a very counterintuitive capability when related to our everyday experience in which light appears to travel instantaneously. By combining this capability with computational imaging techniques, new imaging opportunities emerge such as three dimensional imaging of scenes that are hidden behind a corner, the study of relativistic distortion effects, imaging through diffusive media and imaging of ultrafast optical processes such as laser ablation, supercontinuum and plasma generation. We provide an overview of the main techniques that have been developed for ultra-high speed photography with a particular focus on `light-in-flight' imaging, i.e. applications where the key element is the imaging of light itself at frame rates that allow to freeze it's motion and therefore extract information that would otherwise be blurred out and lost.Comment: Published in Reports on progress in Physic

Multidimensional Fluorescence Imaging and Super-resolution Exploiting Ultrafast Laser and Supercontinuum Technology

This thesis centres on the development of multidimensional fluorescence imaging tools, with a particular emphasis on fluorescence lifetime imaging (FLIM) microscopy for application to biological research. The key aspects of this thesis are the development and application of tunable supercontinuum excitation sources based on supercontinuum generation in microstructured optical fibres and the development of stimulated emission depletion (STED) microscope capable of fluorescence lifetime imaging beyond the diffraction limit. The utility of FLIM for biological research is illustrated by examples of experimental studies of the molecular structure of sarcomeres in muscle fibres and of signalling at the immune synapse. The application of microstructured optical fibre to provide tunable supercontinuum excitation source for a range of FLIM microscopes is presented, including wide-field, Nipkow disk confocal and hyper-spectral line scanning FLIM microscopes. For the latter, a detailed description is provided of the supercontinuum source and semi-confocal line-scanning microscope configuration that realised multidimensional fluorescence imaging, resolving fluorescence images with respect to excitation and emission wavelength, fluorescence lifetime and three spatial dimensions. This included the first biological application of a fibre laser-pumped supercontinuum exploiting a tapered microstructured optical fibre that was able to generate a spectrally broad output extending to ~ 350 nm in the ultraviolet. The application of supercontinuum generation to the first super-resolved FLIM microscope is then described. This novel microscope exploited the concept of STED with a femtosecond mode-locked Ti:Sapphire laser providing a tunable excitation beam by pumping microstructured optical fibre for supercontinuum generation and directly providing the (longer wavelength) STED beam. This STED microscope was implemented in a commercial scanning confocal microscope to provide compatibility with standard biological imaging, and exploited digital holography using a spatial light modulator (SLM) to provide the appropriate phase manipulation for shaping the STED beam profile and to compensate for aberrations. The STED microscope was shown to be capable of recording super resolution in both the lateral and axial planes, according to the settings of the SLM