Download or read book Methods of Attosecond X Ray Pulse Generation written by and published by . This book was released on 2005 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: We review several proposals for generation of solitary attosecond pulses using two types of free electron lasers which are envisioned as future light sources for studies of ultra-fast dynamics using soft and hard x-rays.
Download or read book Modeling Generation and Characterization of Attosecond Pulses written by Siddharth Bhardwaj and published by . This book was released on 2014 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generation of high-order harmonics has emerged as a powerful technique for the generation of broadband coherent radiation in the EUV regime. This has lead to the development of table-top EUV sources that can produce attosecond pulses. These pulses can serve as a probe to resolve atomic attosecond dynamics and image atomic orbitals and molecular motion. Due to high spatial and temporal coherence, high-order harmonic radiation can also be used to seed free electron lasers, which allow the generation of high-intensity X-ray radiation that can be used for imaging biomolecules. Since the first observation of high-order harmonics, effort has been made to accurately model both the generation and the characterization of attosecond pulses. Work on the modeling of high harmonic generation can be divided into two parts: (a) description of the interaction between the JR pulse and atoms that leads to emission of attosecond pulses (the single atom response) and (b) modeling of the propagation of attosecond pulses by accounting for macroscopic phase matching effects. In this work, we will focus on the single atom response which can be calculated either by numerically solving the time dependent Schrodinger equation (TDSE) or through the semi-classical three step model (TSM). In Chapter 2, the theory of light-atom interaction will be reviewed with the focus on the calculation of the dipole trasition matrix element (DTME) in the strong field formalism. It will be shown that the choice of the basis states - Volkov states and Coulomb Volkov states - to describe electrons in the continuum is crucial to the accuracy of DTME calculation. In Chapter 3, the TSM will be derived from the Schrodinger equation by using the saddle point approximation. Through this derivation, the quantum mechanical laser-atom interaction is reduced to a semi-classical model comprising of ionization, propagation and recombination . The numerical scheme for solving the TDSE will be discussed. It will then be used to demonstrate the generation of isolated attosecond pulses from non-sinusoidal sub-cycle pulses. The results of ADK and non-adiabatic ionization models will be compared with that from numerical TDSE, and then used to calculate the harmonic spectra in the tunneling and multi-photon ionization regimes. The recombination step of the TSM, which plays a crucial role in determining the qualitative shape of the high-order harmonic spectrum, will be investigated in Chapter 4. A commonly observed feature of Argon's high-order harmonic spectrum is the presence of a minimum at around 50 eV called the Cooper minimum. The minimum in the high-order harmonic spectrum has been attributed to the minimum in the recombination amplitude. The recombination amplitude will be calculated - in the strong field formalism - using length and acceleration form for two choices of continuum electron wavefunction description (Volkov and Coulomb-Volkov). Attosecond pulse characterization techniques, which are an extension of the subpicosecond pulse characterization technique like FROG and SPIDER, rely on the photoionization process to transfer the amplitude and phase information of the attosecond pulse to the photoelectron spectrum. For accurate pulse characterization, it is crucial to model the photoionization process accurately. Since photoionization and recombination are reverse processes, the improvements in the calculation of the recombination amplitude in Chapter 4, can be used to improve the model function of the pulse retrieval algorithm. It will be shown that the proposed improvements are crucial for accurate characterization of low energy EUV pulses.
Download or read book Towards the Generation of Isolated Attosecond Pulses in the Water Window written by Seth Lucien Cousin and published by . This book was released on 2017 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Attosecond science investigates the realm of processes that happen in fleetingly short passages of time. One attosecond to one second, is what one second is to the age of the universe! Advances in lasers and specifically ultra-short pulsed lasers have opened the door to this extreme frontier of physics. In this thesis I will describe what is required from a laser system in order to access these time scales. The stringent requirements needed motivated us to extensively study, model, redesign and then finally rebuild our laser system making it capable of delivering the necessary laser pulses. Characterisation of these types of laser pulses is essential in making them usable in the pursuit of a fundamental understanding of ultrashort physical processes. Two new characterisation techniques have been developed to add to the suite of tools available to the scientific community to achieve the complicated goal of characterising femtosecond laser pulses. To jump from the femtosecond regime to the attosecond regime, high harmonic generation is currently the defacto method of getting there. I will give a detailed description of our high harmonic beamline, which ultimately is used to perform the first water-window radiation range spectroscopy from a high harmonic source. Intrinsic to the radiation generated for spectroscopy is the sub-femtosecond temporal structure of the radiation. Temporal characterisation of attosecond pulses is traditionally done using the attosecond streaking technique however until now, this technique has not been used in the water-window. X-ray pulses possessing our ultra-broad bandwidth and central photon energy are unprecedented, making this the first time that a streaking experiment is done in this regime.
Download or read book Generation and Characterization of Isolated Attosecond Pulse in the Soft X ray Regime written by Jie Li and published by . This book was released on 2018 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: The observation of any atomic and molecular dynamics requires a probe that has a timescale comparable to the dynamics itself. Ever since the invention of laser, the temporal duration of the laser pulse has been incrementally reduced from several nanoseconds to just attoseconds. Picosecond and femtosecond laser pulses have been widely used to study molecular rotation and vibration.
Download or read book Study on Generation of Attosecond Pulse with Polarization Gating written by Shambhu Ghimire and published by . This book was released on 2007 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Finally, in order to temporarily characterize the attosecond pulses we designed and built an "Attosecond Streak Camera". Most of such cameras to date are limited to measuring a 1 dimensional energy spectrum and have only a few degrees of acceptance angle. Our camera is capable of measuring 2d momentum of the photoelectrons with large acceptance angle, for example ∼65° at the photoelectron of energy ∼15 eV. Recently, we observed the sidebands in addition to the main peaks in their laser assisted XUV photoelectron spectrum. The single attosecond pulses, after being characterized with this high speed camera, can be used to explore the dynamics of electrons at the attosecond scale.
Download or read book Proceedings of the 8th International Conference on Attosecond Science and Technology written by Argenti and published by Springer Nature. This book was released on 2024 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access volume brings together selected papers from the 8th International Conference on Attosecond Science and Technology. The contributions within represent the latest advances in attosecond science, covering recent progress in ultrafast electron dynamics in atoms, molecules, clusters, surfaces, solids, nanostructures and plasmas, as well as the generation of sub-femtosecond XUV and X-ray pulses, either through table-top laser setups or with X-ray free-electron lasers. In addition to highlighting key advances and outlining the state of the field, the conference and its proceedings serve to introduce junior researchers to the community, promote collaborations, and represent the global and topical diversity of the field.
Download or read book Generation of Short and Intense Attosecond Pulses written by Sabih ud Din Khan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Extremely broad bandwidth attosecond pulses (which can support 16as pulses) have been demonstrated in our lab based on spectral measurements, however, compensation of intrinsic chirp and their characterization has been a major bottleneck. In this work, we developed an attosecond streak camera using a multi-layer Mo/Si mirror (bandwidth can support ~100as pulses) and position sensitive time-of-flight detector, and the shortest measured pulse was 107.5as using DOG, which is close to the mirror bandwidth. We also developed a PCGPA based FROG-CRAB algorithm to characterize such short pulses, however, it uses the central momentum approximation and cannot be used for ultra-broad bandwidth pulses. To facilitate the characterization of such pulses, we developed PROOF using Fourier filtering and an evolutionary algorithm. We have demonstrated the characterization of pulses with a bandwidth corresponding to ~20as using synthetic data. We also for the first time demonstrated single attosecond pulses (SAP) generated using GDOG with a narrow gate width from a multi-cycle driving laser without CE-phase lock, which opens the possibility of scaling attosecond photon flux by extending the technique to peta-watt class lasers. Further, we generated intense attosecond pulse trains (APT) from laser ablated carbon plasmas and demonstrated ~9.5 times more intense pulses as compared to those from argon gas and for the first time demonstrated a broad continuum from a carbon plasma using DOG. Additionally, we demonstrated ~100 times enhancement in APT from gases by switching to 400 nm (blue) driving pulses instead of 800 nm (red) pulses. We measured the ellipticity dependence of high harmonics from blue pulses in argon, neon and helium, and developed a simple theoretical model to numerically calculate the ellipticity dependence with good agreement with experiments. Based on the ellipticity dependence, we proposed a new scheme of blue GDOG which we predict can be employed to extract intense SAP from an APT driven by blue laser pulses. We also demonstrated compression of long blue pulses into>240 [mu]J broad-bandwidth pulses using neon filled hollow core fiber, which is the highest reported pulse energy of short blue pulses. However, compression of phase using chirp mirrors is still a technical challenge.
Download or read book Attosecond Pulse Generation and Characterization written by Razvan Cristian Chirla and published by . This book was released on 2011 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: One of the research goals in the DiMauro group is the application of attosecond light pulses for understanding electronic processes and for molecular imaging. The objective of this dissertation work was the construction of an attosecond beamline at The Ohio State University, and the implementation of the so-called Rabbitt technique.
Download or read book Generation and Application of Attosecond Pulses written by Zsolt Diveki and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: To capture electronic rearrangements inside a molecule or during chemical reactions, attosecond (as, 1 as =10-18 s) time resolution is needed. To create a light pulse with this duration, the central frequency has to be in the XUV range and cover several tens of eVs. Moreover, the frequency components have to be synchronized. The so called High Harmonic Generation (HHG) in gases well suits this task. During this process a high intensity laser pulse is focused in a gas jet, where its electric field bends the potential barrier of an atom allowing an electron wave packet (EWP) to tunnel ionize. Following the electric field of the laser the EWP gets accelerated, gaining a large kinetic energy that may be released as a high energy (XUV) photon in the event of a re-collision with the ionic core. These recolliding EWP probe the structure and dynamics of the core in a self-probing scheme: the EWP, that is emitted by the molecule at a certain time, probes itself later. More precisely, this ”self-probing” scheme gives access to the complex valued recombination dipole moment (RDM) of the molecule which is determined by both the nuclear and electronic structure. The recombination encodes these characteristics into the spectral amplitude, phase and polarization state of the harmonic radiation emitted by the dipole. Due to the coherent nature of HHG it is possible to measure all these three parameters. Moreover, it is in principle possible through a tomographic procedure to reconstruct the radiating orbital.The objective of my thesis was two-fold. By implementing advanced characterization techniques of the harmonic amplitude, phase and polarization we studied i) the electronic structure of N2 and laser induced multi-channel tunnel ionization. We presented the reconstruction of molecular orbitals and revealed the ionization channel dependent ultrafast nuclear vibration. We also studied ii) the reflectivity and dispersion of recently designed chirped XUV mirrors that can shape the temporal profile of attosecond pulses. With these mirrors we could control the spectral phase over 20 eV and compensate the GDD of the harmonics or introduce a TOD. We also proposed a novel attosecond pulse shaper.
Download or read book Generation of Few cycle and Attosecond Pulses and Their Use in Probing Ultrafast Dynamics in Gases and Surfaces written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Flux Isolated Attosecond Pulse Generation written by Yi Wu and published by . This book was released on 2013 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis outlines the high intensity tabletop attosecond extreme ultraviolet laser source at the Institute for the Frontier of Attosecond Science and Technology Laboratory. First, a unique Ti:Sapphire chirped pulse amplifier laser system that delivers 14 fs pulses with 300 mJ energy at a 10 Hz repetition rate was designed and built. The broadband spectrum extending from 700 nm to 900 nm was obtained by seeding a two stage Ti:Sapphire chirped pulse power amplifier with mJ-level white light pulses from a gas filled hollow core fiber. It is the highest energy level ever achieved by a broadband pulse in a chirped pulse amplifier up to the current date. Second, using this laser as a driving laser source, the generalized double optical gating method is employed to generate isolated attosecond pulses. Detailed gate width analysis of the ellipticity dependent pulse were performed. Calculation of electron light interaction dynamics on the atomic level was carried out to demonstrate the mechanism of isolated pulse generation. Third, a complete diagnostic apparatus was built to extract and analyze the generated attosecond pulse in spectral domain. The result confirms that an extreme ultraviolet super continuum supporting 230 as isolated attosecond pulses at 35 eV was generated using the generalized double optical gating technique. The extreme ultraviolet pulse energy was 100 nJ at the exit of the argon gas target.
Download or read book Towards Intense Single Attosecond Pulse Generation from a 400 NM Driving Laser written by Yan Cheng and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Attosecond pulse generation is a powerful tool to study electron dynamics in atoms and molecules. However, application of attosecond pulses is limited by the low photon flux of attosecond sources. Theoretical models predict that the harmonic efficiency scales as [lambda][superscript]-6 in the plateau region of the HHG spectrum, where [lambda] is the wavelength of the driving laser. This indicates the possibility of generating more intense attosecond pulses using short wavelength driving lasers. The purpose of this work is to find a method to generate intense single attosecond pulses using a 400 nm driving laser. In our experiments, 400 nm femtosecond laser pulses are used to generate high harmonics. First, the dependence of the high harmonic generation yield on the ellipticity of 400 nm driving laser pulse is studied experimentally, and it is compared with that of 800 nm driving lasers. A semi-classical theory is developed to explain the ellipticity dependence where the theoretical calculations match experiment results very well. Next, 400 nm short pulses (sub-10 fs) are produced with a hollow core fiber and chirped mirrors. Finally, we propose a scheme to extract single attosecond pulses with the Generalized Double Optical Gating (GDOG) method.
Download or read book Generation and Characterization of Attosecond Pulses written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The research undertaken in this project has been directed toward the area of attoscience, in particular the problem of attosecond metrology. That is, the accurate determination of the electric field of attosecond XUV radiation. This outstanding problem has been identified as a critical technology for further development of the field, and our research adds to the area by providing the first method for characterization using the harmonic radiation itself as a tool. The technical effectiveness of this approach is very high, since it is vastly easier to detect XUV radiation directly than via the spectrum of photoelectrons liberated from atoms by it. This means that the experimental data rate can be much higher in principle using all-optical detection that electron detection, which will greatly aid the utility of harmonic XUV sources in attoscience applications. There are as yet no direct public benefits from this area of scientific research, though access to material structural dynamics on unprecedented brief timescales are expected to yield significant benefits for the future.
Download or read book Generation and Characterization of Sub 70 Isolated Attosecond Pulses written by Qi Zhang and published by . This book was released on 2014 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamics occurring on microscopic scales, such as electronic motion inside atoms and molecules, are governed by quantum mechanics. However, the Schrödinger equation is usually too complicated to solve analytically for systems other than the hydrogen atom. Even for some simple atoms such as helium, it still takes months to do a full numerical analysis. Therefore, practical problems are often solved only after simplification. The results are then compared with the experimental outcome in both the spectral and temporal domain. For accurate experimental comparison, temporal resolution on the attosecond scale is required. This had not been achieved until the first demonstration of the single attosecond pulse in 2001. After this breakthrough, "attophysics" immediately became a hot field in the physics and optics community. While the attosecond pulse has served as an irreplaceable tool in many fundamental research studies of ultrafast dynamics, the pulse generation process itself is an interesting topic in the ultrafast field. When an intense femtosecond laser is tightly focused on a gaseous target, electrons inside the neutral atoms are ripped away through tunneling ionization. Under certain circumstances, the electrons are able to reunite with the parent ions and release photon bursts lasting only tens to hundreds of attoseconds. This process repeats itself every half cycle of the driving pulse, generating a train of single attosecond pulses which lasts longer than one femtosecond. To achieve true temporal resolution on the attosecond time scale, single isolated attosecond pulses are required, meaning only one attosecond pulse can be produced per driving pulse.
Download or read book Generation of Attosecond Light Pulses from Gas and Solid State Media written by Stefanos Chatziathanasiou and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Attosecond Angular Streaking written by Petrissa Eckle and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2009 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis a new technique called 'attosecond angular streaking' (AAS) was applied for the first time. AAS allows to resolve ionization dynamics in the strong field regime with attosecond accuracy using only femtosecond pulses. In this regime, ionization mainly proceeds via tunneling through an energetically forbidden barrier. The process of tunneling is a fundamental and well-understood phenomenon in quantum mechanics. However, attempts to measure the 'tunneling time' have produced controversial results, partly due to the difficulty of defining a temporal operator in quantum mechanics, making it difficult to compare experiments. In this thesis, the question is addressed of whether the tunneling rate can adjust instantaneously to a changing barrier or if there is a delay between the field that defines the barrier and the corresponding tunneling ionization rate. It was found that indeed, no delay between the electric field and the corresponding tunneling rate exists within an experimental error limit of 12 attoseconds.
Download or read book Towards High flux Isolated Attosecond Pulses with a 200 TW CPA written by Eric Cunningham and published by . This book was released on 2015 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: To obtain the microjoule-level attosecond pulse energy required for performing all-attosecond experiments, the attosecond flux generated by the IFAST 10 TW system was still deficient by an order of magnitude. To this end, the laser system was upgraded to provide joule-level output energies while maintaining pulse compression to 15 fs, with a targeted peak power of 200 TW. This was accomplished by adding an additional Ti:sapphire amplifier to the existing 10 TW system and implementing a new pulse compression system to accommodate the higher pulse energy. Because this system operated at a 10 Hz repetition rate, stabilization of the carrier-envelope phase (CEP)--important for controlling attosecond pulse production--could not be achieved using traditional methods. Therefore, a new scheme was developed, demonstrating the first-ever control of CEP in a chirped-pulse amplifier (CPA) at low repetition rates. Finally, a new variation of optical gating was proposed as a way to improve the efficiency of the attosecond pulse generation process. This method was also predicted to allow for the generation of isolated attosecond pulses with longer driving laser pulses, as well as the extension of the highenergy photon cut-off of the XUV continuum.
