Improvements for Generating High-Order Harmonics and Attosecond Pulses with Ultrashort Laser Fields PDF Download
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Author: Dian Peng
Publisher:
ISBN: 9781392857038
Category : Laser pulses, Ultrashort
Languages : en
Pages : 0
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Book Description
Nonlinear processes of high-order harmonic generation (HHG) produced by ultrashort few-cycle laser pulses possess interesting features which HHG produced by long pulses of many cycles may not have. First, HHG spectra produced by ultrashort pulses are extremely sensitive to the driving pulse waveform, which can be controlled by laser parameters such as carrier-envelope phases (CEPs), time delays or frequency chirps. Second, HHG spectra produced by ultrashort pulses can exhibit broad uneven peaks which are different from usual odd-ordered harmonic peaks that long pulses produce. Based on the high sensitivity on pulse waveform of HHG spectra produced by ultrashort pulses, we investigate for a two-color few-cycle pulse how HHG can be enhanced by the use of time delays or frequency chirps. Both a numerical and an analytic method are employed to calculate HHG spectra from a single H atom. For the time delay case, our results show that a time delay between the two-color, few-cycle pulses can increase the intensity of an HHG spectrum by an order of magnitude (or more) compared to the no-time-delay case at the cost of a reduction in the HHG plateau cutoff energy. For the frequency chirp case, we show how changing signs of chirps in each of the two component few-cycle pulses leads to drastic changes in the HHG spectra. Both time-frequency analyses from the numerical method and a semiclassical interpretation from the analytic method provide clear physical explanations of how HHG spectra are changed by those time delays and chirp signs.Based on the broad uneven peaks in HHG spectra produced by ultrashort pulses, we investigate how the duration of an isolated attosecond pulse can be minimized by carefully selecting frequencies in an HHG spectrum and provide a solution for the attochirp problem in generating attosecond pulses. Specifically, three frequency-selection categories are studied: a single spectral range between cutoffs, a single spectral range across cutoff and a striped-frequency range. Our results show that among all three categories the striped-frequency range produces the shortest and strongest attosecond pulses for a broad HHG spectrum with transform-limited duration.
Author: Dian Peng
Publisher:
ISBN: 9781392857038
Category : Laser pulses, Ultrashort
Languages : en
Pages : 0
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Book Description
Nonlinear processes of high-order harmonic generation (HHG) produced by ultrashort few-cycle laser pulses possess interesting features which HHG produced by long pulses of many cycles may not have. First, HHG spectra produced by ultrashort pulses are extremely sensitive to the driving pulse waveform, which can be controlled by laser parameters such as carrier-envelope phases (CEPs), time delays or frequency chirps. Second, HHG spectra produced by ultrashort pulses can exhibit broad uneven peaks which are different from usual odd-ordered harmonic peaks that long pulses produce. Based on the high sensitivity on pulse waveform of HHG spectra produced by ultrashort pulses, we investigate for a two-color few-cycle pulse how HHG can be enhanced by the use of time delays or frequency chirps. Both a numerical and an analytic method are employed to calculate HHG spectra from a single H atom. For the time delay case, our results show that a time delay between the two-color, few-cycle pulses can increase the intensity of an HHG spectrum by an order of magnitude (or more) compared to the no-time-delay case at the cost of a reduction in the HHG plateau cutoff energy. For the frequency chirp case, we show how changing signs of chirps in each of the two component few-cycle pulses leads to drastic changes in the HHG spectra. Both time-frequency analyses from the numerical method and a semiclassical interpretation from the analytic method provide clear physical explanations of how HHG spectra are changed by those time delays and chirp signs.Based on the broad uneven peaks in HHG spectra produced by ultrashort pulses, we investigate how the duration of an isolated attosecond pulse can be minimized by carefully selecting frequencies in an HHG spectrum and provide a solution for the attochirp problem in generating attosecond pulses. Specifically, three frequency-selection categories are studied: a single spectral range between cutoffs, a single spectral range across cutoff and a striped-frequency range. Our results show that among all three categories the striped-frequency range produces the shortest and strongest attosecond pulses for a broad HHG spectrum with transform-limited duration.
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Languages : en
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Author: Luca Fedeli
Publisher: Springer
ISBN: 3319442902
Category : Science
Languages : en
Pages : 194
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Book Description
This thesis describes pioneering research on the extension of plasmonics schemes to the regime of high-intensity lasers. By presenting a rich and balanced mix of experimentation, theory and simulation, it provides a comprehensive overview of the emerging field of high field plasmonics, including open issues and perspectives for future research. Combining specially designed targets and innovative materials with ultrashort, high-contrast laser pulses, the author experimentally demonstrates the effects of plasmon excitation on electron and ion emission. Lastly, the work investigates possible further developments with the help of numerical simulations, revealing the potential of plasmonics effects in the relativistic regime for advances in laser-driven sources of radiation, and for the manipulation of extreme light at the sub-micron scale.
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Languages : en
Pages :
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This project has pursued the possibility of producing ultra-short pulses of coherent light using harmonic conversion of a mid-infrared light source, focused into an atomic gas medium. This was a joint effort with Louis DiMauro's experimental group at Brookhaven National Laboratory and in collaboration with Ken Schafer from Louisiana State University and Mette Gaarde from Lund University on the theoretical part. High order harmonic generation (HHG) in nobel gas media using short-pulse visible and near infrared lasers has become an established method for producing coherent, short pulse radiation at wavelengths from the ultraviolet to soft x-rays. We recently proposed that this approach could lead to extremely short pulses, potentially less than one fs, provided the unavoidable frequency chirp of the highest harmonics, could be removed by compressing the pulses with a grating pair. Sources of sub-fs pulses would provide unique opportunities to study dynamical processes on time scales short compared to those associated with nuclear motion. Truly stroboscopic pictures of chemical reaction dynamics would be possible, for example. In this research project we have chosen much smaller driving frequencies than used previously in HHG studies for two reasons. First, this will allow us to measure the pulse lengths of the compressed harmonics because they will be in the vacuum ultraviolet where coincidence measurements are possible. Second, the wavelengths of these harmonics will be idea for pump-probe experiments of quantum dynamical control studies. Our theoretical effort was concentrated in two areas. We used our time-dependent quantum numerical codes to evaluate the harmonic response of alkali atoms to the mid-IR laser excitation. Results were obtained for potassium, the initial species to be used in the experiments, then sodium and rubidium to investigate the possibility of higher conversion efficiencies. In fact, rubidium was found to be significantly better than potassium, both because it provided a stronger harmonic response and because the target gas could be maintained at about an order of magnitude higher pressure than with potassium. The second theoretical focus was the development of an adiabatic approximation for solving the equations governing the propagation of the generated harmonic fields through the laser-excited medium. A code was constructed using this approximation and the first phase matching calculations in this ultra-short pulse regime were carried out. The experimental effort was slowed by difficulties with the potassium source which were solved and photoelectron and harmonic spectra were obtained, the first ever at these wavelengths. These preliminary experiments were carried out using a ps laser source and an estimate of the bandwidth of the harmonics was obtained. The spectral width indicated that our prediction that the harmonic pulse lengths can be two orders of magnitude shorter than the driving field appears probable. Soon the experiments will switch to a 100 fs driver and the attempt to reach the sub-fs regime will then be possible. W e found that potassium, the target in the initial studies had a lower than expected conversion efficiency so that experiments were initiated using rubidium. This has proved to be better by more than three orders of magnitude. A large fraction of this improvement was due to the metal source running at a much higher pressure. A further increase will be obtained when the shorter pulse driver is installed. An additional paper on these preliminary results is now being prepared. The project was quite successful, although a bit behind schedule because of experimental problems. The theoretical predictions seem to have been corroborated by the measurements thus far. We also found some unexpected differences in the behavior of the different alkali atoms to mulitphoton excitation and ionization at these wavelengths.
Author: Rashid Ganeev
Publisher: World Scientific
ISBN: 9813208279
Category : Science
Languages : en
Pages : 297
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Book Description
It is interesting to analyze the application of mid-infrared (MIR, 1000-5000 nm) radiation to study the dynamics of the nonlinear optical response of ablated molecular structures compared with commonly used Ti: sapphire lasers for plasma high-order harmonic generation (HHG), including the studies of extended harmonics at a comparable conversion efficiency with shorter wavelength laser sources, and a search for new opportunities in improvement of the HHG conversion efficiency in the mid-IR range, such as the application of clustered molecules. This book shows the most recent findings of various new schemes of the application of MIR pulses for HHG in laser-produced low-ionised, low-density plasma plumes, which could be dubbed for simplicity as 'plasma harmonics'. The use of any element of the periodic table, as well as thousands of complex samples that exist as solids largely extends the range of materials employed, whereas only a few rare gases are typically available for gas HHG. The exploration of practically any solid-state material through the nonlinear spectroscopy comprising laser ablation and harmonic generation can be considered as a new tool for materials science. Thus the MIR pump based laser-ablation-induced high-order harmonic generation spectroscopy can be considered a new method for the study of materials and one of most important applications of plasma HHG.
Author: Claude Rulliere
Publisher: Springer Science & Business Media
ISBN: 0387017690
Category : Science
Languages : en
Pages : 438
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Book Description
This is the second edition of this advanced textbook written for scientists who require further training in femtosecond science. Four years after pub- cation of the ?rst edition, femtosecond science has overcome new challenges and new application ?elds have become mature. It is necessary to take into account these new developments. Two main topics merged during this period that support important scienti?c activities: attosecond pulses are now gen- ated in the X-UV spectral domain, and coherent control of chemical events is now possible by tailoring the shape of femtosecond pulses. To update this advanced textbook, it was necessary to introduce these ?elds; two new ch- ters are in this second edition: “Coherent Control in Atoms, Molecules, and Solids”(Chap.11)and“AttosecondPulses”(Chap.12)withwell-documented references. Some changes, addenda, and new references are introduced in the ?rst edition’s ten original chapters to take into account new developments and updatethisadvancedtextbookwhichistheresultofascienti?cadventurethat started in 1991. At that time, the French Ministry of Education decided that, in view of the growing importance of ultrashort laser pulses for the national scienti?c community, a Femtosecond Centre should be created in France and devoted to the further education of scientists who use femtosecond pulses as a research tool and who are not specialists in lasers or even in optics.
Author: Zenghu Chang
Publisher: CRC Press
ISBN: 1420089382
Category : Science
Languages : en
Pages : 536
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Book Description
Attosecond optical pulse generation, along with the related process of high-order harmonic generation, is redefining ultrafast physics and chemistry. A practical understanding of attosecond optics requires significant background information and foundational theory to make full use of these cutting-edge lasers and advance the technology toward the n
Author: Rashid A Ganeev
Publisher: Springer
ISBN: 9811001944
Category : Science
Languages : en
Pages : 230
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Book Description
This book offers a review of the use of extended ablation plasmas as nonlinear media for HHG of high-order harmonic generation (HHG). The book describes the different experimental approaches, shows the advantages and limitations regarding HHG efficiency and discusses the particular processes that take place at longer interaction lengths, including propagation and quasi-phase matching effects. It describes the most recent approaches to harmonic generation in the extreme ultraviolet (XUV) range with the use of extended plasma plumes, and how these differ from more commonly-used gas-jet sources. The main focus is on studies using extended plasmas, but some new findings from HHG experiments in narrow plasma plumes are also discussed. It also describes how quasi-phase-matching in modulated plasmas, as demonstrated in recent studies, has revealed different means of tuning enhanced harmonic groups in the XUV region. After an introduction to the fundamental theoretical and experimental aspects of HHG, a review of the most important results of HHG in narrow plasmas is presented, including recent studies of small-sized plasma plumes as emitters of high-order harmonics. In Chapter 2, various findings in the application of extended plasmas for harmonic generation are analyzed. One of the most important applications of extended plasmas, the quasi-phase-matching of generated harmonics, is demonstrated in Chapter 3, including various approaches to the modification of perforated plasma plumes. Chapter 4 depicts the nonlinear optical features of extended plasmas produced on the surfaces of different non-metal materials. Chapter 5 is dedicated to the analysis of new opportunities for extended plasma induced HHG. The advantages of the application of long plasma plumes for HHG, such as resonance enhancement and double-pulse method, are discussed in Chapter 6. Finally, a summary section brings together all of these findings and discuss the perspectives of extended plasma formations for efficient HHG and nonlinear optical plasma spectroscopy. The book will be useful for students and scholars working in this highly multidisciplinary domain involving material science, nonlinear optics and laser spectroscopy. It brings the new researcher to the very frontier of the physics of the interaction between laser and extended plasma; for the expert it will serve as an essential guide and indicate directions for future research.
Author: Luis Plaja
Publisher: Springer
ISBN: 3642376231
Category : Science
Languages : en
Pages : 281
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Book Description
Attophysics is an emerging field in physics devoted to the study and characterization of matter dynamics in the sub-femtosecond time scale. This book gives coverage of a broad set of selected topics in this field, exciting by their novelty and their potential impact. The book is written review-like. It also includes fundamental chapters as introduction to the field for non-specialist physicists. The book is structured in four sections: basics, attosecond pulse technology, applications to measurements and control of physical processes and future perspectives. It is a valuable reference tool for researchers in the field as well as a concise introduction to non-specialist readers.
Author: Rashid A. Ganeev
Publisher: World Scientific
ISBN: 1848169809
Category : Science
Languages : en
Pages : 250
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Book Description
This book represents the first comprehensive treatment of high-order harmonic generation in laser-produced plumes, covering the principles, past and present experimental status and important applications. It shows how this method of frequency conversion of laser radiation towards the extreme ultraviolet range matured over the course of multiple studies and demonstrated new approaches in the generation of strong coherent short-wavelength radiation for various applications. Significant discoveries and pioneering contributions of researchers in this field carried out in various laser scientific centers worldwide are included in this first attempt to describe the important findings in this area of nonlinear spectroscopy. High-Order Harmonic Generation in Laser Plasma Plumes is a self-contained and unified review of the most recent achievements in the field, such as the application of clusters (fullerenes, nanoparticles, nanotubes) for efficient harmonic generation of ultrashort laser pulses in cluster-containing plumes and resonance-induced enhancement of harmonic yield. It can be used as an advanced monograph for researchers and graduate students working in the field of nonlinear spectroscopy. It is also suitable for researchers in laser physics and nonlinear optics who wish to have an overview of the advanced achievements in laser ablation-induced high-order harmonic generation spectroscopy. The carefully presented details of this book will be of value to research devoted to the understanding and control frequency conversion of laser pulses in plasma plumes. The studies described in this book pave the way for the development of a new method of materials studies using the laser ablation-induced high-order harmonic generation spectroscopy, which can exploit the spectral and structural properties of various solid-state materials through their ablation and further propagation of short laser pulse through laser-produced plasma and generation of high-order harmonics.
