Few-cycle Pulses Amplification For Attosecond Science Applications Modeling And Experiments

The emergence of mode-locked oscillators providing pulses with durations as short as a few electric-field cycles in the near infra-red has paved the way toward electric-field sensitive physics experiments. In addition, the control of the relative phase between the carrier and the pulse envelope, developed in the early 2000’s and rewarded by a Nobel price in 2005, now provides unprecedented control over the pulse behaviour. The amplification of such pulses to the millijoule level has been an on-going task in a few world-class laboratories and has triggered the dawn of attoscience, the science of events happening on an attosecond timescale. This work describes the theoretical aspects, modeling and experimental implementation of HERACLES, the Laser Plasma Laboratory optical parametric chirped pulse amplifier (OPCPA) designed to deliver amplified carrier-envelope phase stabilized 8-fs pulses with energy beyond 1 mJ at repetition rates up to 10 kHz at 800 nm central wavelength. The design of the hybrid fiber/solid-state amplifier line delivering 85-ps pulses with energy up to 10 mJ at repetition rates in the multi-kHz regime tailored for pumping the optical parametric amplifier stages is presented. The novel stretcher/compressor design of HERACLES, suitable for handling optical pulses with spectra exceeding 300 nm of bandwidth with unprecedented flexibility, is fully modeled and also presented in the frame of this thesis. Finally, a 3D model of the multistage non-collinear optical parametric amplifier is also reported. The current and foreseen overall performances of HERACLES are presented. This facility is designed to enable attosecond physics experiments, high-harmonic generation and physics of plasma studies

Ultrafast pulse dynamics in low noise Tm/Ho doped mode-locked fiber lasers

Mode-locked fiber lasers have attracted significant scientific and commercial interest since they offer a compact and highly stable platform with straightforward operation for exploiting ultrafast and nonlinear phenomena. They have enabled a vast range of applications that span from distinct disciplines such as medical diagnostics, molecular spectroscopy, and high-power precise mechanical cutting, to optical metrology. Various gain media have been utilized to achieve laser emission at different wavelengths. We have developed unique thulium/holmium (Tm/Ho) doped mode-locked fiber laser systems to address the needs of low-noise ultrafast optical sources in the wavelength vicinity of 2 μm at higher repetition rates. Since the 2 μm wavelength regime has recently attracted more attention with the emergence of thulium gain fibers, the rich underlying cavity dynamics, novel pulse operation regimes and nonlinear phenomena in compact fiber configurations have not been fully explored yet. In this thesis, research is conducted on novel Tm fiber laser cavity configurations and on the formation of unique, polarization-based pulsing regimes. Particularly, this research is focused on the exploration of novel ultrafast and nonlinear phenomena, and the development of optical sources emitting unprecedented ultrafast pulse trains beyond conventional equal-intensity distribution using Tm/Ho doped gain media. The research presented features four main results: 1) development of a high repetition rate and low-noise Tm/Ho doped mode-locked fiber laser platform as an attractive optical source for a wide variety of applications 2) investigation of a novel mode-locked state in which the ultrafast pulse train is composed of co-generated, consecutive, equal intensity and orthogonally polarized pulses in order to achieve dual RF comb generation for dual-comb spectroscopy applications, 3) exploration of controllable ultrafast waveform generation utilizing vector soliton and harmonic mode-locking mechanisms for optical telecommunication applications, and 4) demonstration of unique transitional mode-locked states showing exceptional features such as powerful irregular bursts of ultrafast pulses and rogue wave behavior without damaging the laser elements. The aim of these projects has been to explore the novel optical properties of Tm/Ho co-doped fiber lasers in order to achieve advanced functionalities in commonly practiced applications such as telecommunication, metrology and spectroscopic applications.2019-10-22T00:00:00

Pulse-Shape Analysis of PDM-QPSK Modulation Formats for 100 and 200 Gb/s DWDM transmissions

Advanced optical modulation format polarization-division multiplexed quadrature phase shift keying (PDM-QPSK) has become a key ingredient in the design of 100 and 200-Gb/s dense wavelength-division multiplexed (DWDM) networks. The performance of this format varies according to the shape of the pulses employed by the optical carrier: non-return to zero (NRZ), return to zero (RZ) or carrier-suppressed return to zero (CSRZ). In this paper we analyze the tolerance of PDM-QPSK to linear and nonlinear optical impairments: amplified spontaneous emission (ASE) noise, crosstalk, distortion by optical filtering, chromatic dispersion (CD), polarization mode dispersion (PMD) and fiber Kerr nonlinearities. RZ formats with a low duty cycle value reduce pulse-to-pulse interaction obtaining a higher tolerance to CD, PMD and intrachannel nonlinearities

Design, optimization, and applications of few-cycle Ti:Sapphire lasers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Vita. Cataloged from PDF version of thesis.Includes bibliographical references (p. 183-195).Ti:Sapphire mode-locked lasers are a unique technology that enables a wide variety of applications. Owing to the ultrabroadband nature of the Ti:sapphire crystal and the invention of precisely engineered dispersion-compensating mirrors (DCMs), these lasers are now capable of generating stable pulse trains directly with octave-spanning spectrum, few-cycle pulse duration, and a desired repetition rate from a compact system. This paves the way to a new world of emerging applications ranging from the search of exoplanets, high-harmonic generation, to precision measurement Qualitatively, the key to the stable mode-locking of Ti:Sapphire lasers lies in the balance of various spatial and temporal nonlinear effects such as self-amplitude modulation(SAM), self-phase modulation(SPM), saturable absorption, self-focusing, gain-filtering, gain-guiding, and so on. However, since much shorter pulses and much higher intracavity intensities are often reached inside the laser gain medium, the spatiotemporal dynamics in such lasers are even more complicated as non-negligible multi-photon processes also come into play. Due to the strong coupling between these effects, performing a reliable analysis and optimization become extremely challenging. In this thesis we study the spatiotemporal dynamics of pulse evolution in the few-cycle regime and provide guidelines for designing and optimizing these lasers for repetition rate ranging from 85 MHz to 2 GHz. The essential background reviews as well as key concepts in KLM lasers will be given together with a demonstration of octave-spanning Ti:sapphire lasers with record-high repetition rate. A numerical model for simulating the full spatiotemporal dynamics is introduced. For an efficient numerical calculation, GPU accelerated computing techniques are adopted. With this model, many unique features that are observed from the experiments can be simulated for the first time. A novel type of output coupler called gain-matched output coupler is introduced which can greatly reduce the nonlinearity required for ultrabroadband mode-locking. Already at pump power levels close to the cw lasing threshold it is possible to initiate robust mode-locking and generate <8 fs output pulses from Ti:sapphire lasers with excellent beam quality operating in the center of its stability range. Moreover, the development of visible astro-combs based on fewcycle Ti:sapphire lasers will be discussed. This application is enabled by two promising technologies (broadband zero-GDD mirror sets and Cherenkov radiation in the few-cycle regime) which are developed to increase the repetition rate and spectral coverage of the laser systems operated in the few-cycle regime. Fiber-optic Cherenkov radiation in the few-cycle regime excited by sub-10fs Ti:sapphire pulses is studied. Through a dispersion-engineered PCF driven by a few-cycle pulse, the nonlinearity can produce highly efficient broadband frequency up-conversion to the visible wavelength range. Finally, we propose and demonstrate a new approach for broadband dispersion-free optical cavities using a zero-GDD mirror set; With the first zero-GDD mirror pair, the construction of a -40 GHz filtering cavity with 100 nm bandwidth for a green astro-comb (480-580 nm) was demonstrated. Finally, the thesis is concluded by discussing the practical issues related to the construction of a easy-to-operate, long-term stable few-cycle Ti:sapphire laser.by Li-Jin Chen.Ph.D

Advances in Optical Amplifiers

Optical amplifiers play a central role in all categories of fibre communications systems and networks. By compensating for the losses exerted by the transmission medium and the components through which the signals pass, they reduce the need for expensive and slow optical-electrical-optical conversion. The photonic gain media, which are normally based on glass- or semiconductor-based waveguides, can amplify many high speed wavelength division multiplexed channels simultaneously. Recent research has also concentrated on wavelength conversion, switching, demultiplexing in the time domain and other enhanced functions. Advances in Optical Amplifiers presents up to date results on amplifier performance, along with explanations of their relevance, from leading researchers in the field. Its chapters cover amplifiers based on rare earth doped fibres and waveguides, stimulated Raman scattering, nonlinear parametric processes and semiconductor media. Wavelength conversion and other enhanced signal processing functions are also considered in depth. This book is targeted at research, development and design engineers from teams in manufacturing industry, academia and telecommunications service operators

Vector Soliton Fiber Lasers

Solitons, as stable localized wave packets that can propagate long distance in dispersive media without changing their shapes, are ubiquitous in nonlinear physical systems. Since the first experimental realization of optical bright solitons in the anomalous dispersion single mode fibers (SMF) by Mollenauer et al. in 1980 and optical dark solitons in the normal dispersion SMFs by P. Emplit et al. in 1987, optical solitons in SMFs had been extensively investigated. In reality a SMF always supports two orthogonal polarization modes. Taking fiber birefringence into account, it was later theoretically predicted that various types of vector solitons, including the bright-bright vector solitons, dark-dark vector solitons and dark-bright vector solitons, could be formed in SMFs. However, except the bright-bright type of vector solitons, other types of vector solitons are so far lack of clear experimental evidence. Optical solitons have been observed not only in the SMFs but also in mode locked fiber lasers. It has been shown that the passively mode-locked erbium-doped fiber lasers offer a promising experimental platform for studying the scalar optical solitons. Vector solitons can also be formed in mode locked fiber lasers. In this dissertation, the author presents results of a series of theoretical and experimental investigations on the vector solitons in fiber lasers.Comment: This is a PhD thesis on vector soliton fiber laser

Development of passive ultrafast fiber lasers at telecom wavelengths using indium nitride as saturable absorber

This thesis focuses on the research of new technologies for fabrication of passive ultrafast mode-locked fiber lasers, operating at telecom wavelengths (C-band, 1.53-1.57 μm). For this purpose novel saturable absorbers based on indium nitride (InN) are proposed, which have been deposited using molecular beam epitaxy. This material presents unique properties such as direct band gap energy, high thermal and chemical stability, and high radiation hardness. In this thesis, the InN based structures have been completely characterized, being particularly detailed the optical characterization of both the linear and nonlinear behavior. The developed devices have demonstrated high nonlinear optical effects, with modulation depth over 30%. Moreover, they have proved to support over 100 mJ/cm2, with no sign of apparent optical damage, converting them in promising devices for high energy applications. Also, the design and fabrication of laser resonators have been carried out. For this purpose, optical fiber has been used as active medium, besides the InN-based saturable absorbers for achievement of the mode-locking. The developed lasers deliver ultrashort pulses (200-250 fs) with high peak power (over 40 kW). Furthermore, all the lasers using InN based saturable absorbers have exhibited properties such as polarization independence or self-starting operation. For all the experiments that have been performed along this work, InN can be situated as a promising material for application in the design of ultrafast lasers with emission at telecom wavelengths

Laser Pulses

This book discusses aspects of laser pulses generation, characterization, and practical applications. Some new achievements in theory, experiments, and design are demonstrated. The introductive chapter shortly overviews the physical principles of pulsed lasers operation with pulse durations from seconds to yoctoseconds. A theory of mode-locking, based on the optical noise concept, is discussed. With this approximation, all paradoxes of ultrashort laser pulse formation have been explained. The book includes examples of very delicate laser operation in biomedical areas and extremely high power systems used for material processing and water purification. We hope this book will be useful for engineers and managers, for professors and students, and for those who are interested in laser science and technologies

Implementation of Ultrafast Optical Characterization Techniques

The single beam Z-Scan technique, a two beam Pulse-Delay Modulation Technique (PDMT), and a combination of these methods are implemented to measure both nonlinear absorption and nonlinear refraction in semiconductors. The laser source used is a Kerr Lens Modelocked (KLM) Ti:sapphire laser producing tunable near IR 100 femtosecond pulses of ~5 nJ of energy per pulse at a 90 MHz repetition rate. Specifically we monitor two photon absorption and the bound electronic nonlinear refraction in ZnSe and this nonlinear refraction in ZnS. These techniques open the spectral range where these nonlinear optical parameters can be measured by allowing tunable high repetition rate low pulse energy lasers to be used. In the past such measurements have been made primarily with high energy low repetition rate lasers such as Q-switched or modelocked and Q-switched Nd3+:YAG lasers and its harmonics or Nd3+:YAG pumped dye lasers. Such dye lasers while tunable are difficult to use and require organic dyes and solvents which may be flammable and/or carcinogenic. Recently, the solid state KLM Ti:sapphire laser has also been used to pump broadly tunable Optical Parametric Oscillators. The techniques discussed in this thesis will also allow such sources to be used for nonlinear optical measurements. Additionally, these material measurement techniques have a great deal in common with autocorrelation pulse width measurement techniques. Therefore, this thesis also discusses the pulse width measurement techniques that we used to characterize our laser system