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Attosecond Laser Generation
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
Recently attosecond and nanoscale physics are two areas of research that came together. The interaction of ultrashort laser pulses on the timescale of femtosecond and sub-femtosecond duration, with the atoms, molecules, or solids has been dealt with in attosecond physics. Therefore, the measurement, control, and finally the manipulation of electron dynamics on the timescale of attoseconds can be made. These electron dynamics gives the information about the chemical and physical changes that occur at fundamental levels. A single isolated pulse of attosecond duration is possible to generate, as confirmed by the several researchers (Hentschel et al. 2001; Kienberger et al. 2004; Sansone et al. 2006; Schultze et al. 2007; Goulielmakis et al. 2008; Mashiko et al. 2008) and it finds applications (Goulielmakis et al. 2004; Uiberacker et al. 2007) in investigation of faster processes such as on the atomic scale. The aim of the attosecond science is to probe the electronic motion on the atomic length scale. More specifically, it belongs to the ultra-fast motion of the charges (including holes, electrons, and also protons in some cases) and interactions among themselves.
Theoretical Atto-nano Physics
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
This concept of tunnel ionization underpins many important theoretical advances, which have received crystal-clear experimental confirmation with the development of intense ultrashort lasers and attosecond sources over the past two decades. On a fundamental level, theoretical and experimental progress opened the door to the study of basic atomic and molecular processes on the attosecond timescale. On a practical level, this led to the development of attosecond high-frequency extreme ultraviolet (XUV) and X-ray sources, which promise many important applications, such as fine control of atomic and molecular reactions among others. The very fact that we deal here with sources that produce pulses of attosecond duration is remarkable. Attosecond XUV pulses allow, in principle, to capture all processes underlying structural dynamics and chemical reactions, including electronic motion coupled to nuclear dynamics. They also allow to address the basic unresolved and controversial questions in quantum mechanics, such as, for instance, the duration of the strong-field ionization process or the so-called tunnelling time [61,85].
Effects of pressure on the femtosecond filamentation with HOKE in air
Published in Gin Jose, Mário Ferreira, Advances in Optoelectronic Technology and Industry Development, 2019
The filamentation under the non-standard-atmosphere pressures has also been studied numerically based on the classical model. When the pressure is about 10 atm, the GVD has a great influence on the collapse distance (Li et al. 2014). The laser noise is compressed by filamentation in argon at about 5 atm pressure (Béjot et al. 2007). The pulse with the duration as short as 2.5 attoseconds can be achieved under 80 atm (Popmintchev et al. 2012). The influence of the input beam shape, chirp and pulse duration on the length of the filament channels is discussed from 0.2 atm to 1 atm (Couairon et al. 2006), and the filament length becomes more homogeneous at higher altitude when the input peak power is fixed (Hosseini et al. 2012).
Generation of carrier-envelope phase-controlled isolated attosecond pulses using chirped femtosecond excitation lasers
Published in Journal of Modern Optics, 2019
H. A. Navid, R. Aghbolaghi, Z. Yarali
In summary, the high order harmonics are calculated by numerical solution of the time-dependent Schrödinger equation for the one-dimensional hydrogen atom, driven by the chirped laser pulse. We explore the possibility of generating isolated transform-limited attosecond pulses, including our predefined values for the carrier-envelope phase, central frequency, and duration. A proper cost function, containing the necessary information of the desired field, is defined for the genetic algorithm. The presented method is efficient and can be easily extended to generate any shaped XUV fields such as non-transform limited or non-isolated pulses. We verify the efficiency of the method by generating our four predefined attosecond pulses defined by (1):, (2): , (3): as, and (4): as. Optimized values of the driving laser parameters, derived by minimizing the cost function, are available experimentally. The resulting attosecond pulse properties are computed and then compared with those of the desired ones. We confirm that the resulting XUV pulses satisfy the favourite requirements suitably. The physical mechanisms are discussed based on the wavelet time–frequency profile analysis. The introduced method is very promising since the resulting attosecond pulses originated from the short trajectories are preferred in experiments because of their unique spectral and spatial properties.
Probing time-resolved emission in laser-driven electron-multirescattering in a high-order harmonic generation
Published in Journal of Modern Optics, 2019
Peng-Cheng Li, Chun-Xiao Li, Xiong-Yuan Lei, Yae-Lin Sheu, Xiao-Xin Zhou, Shih-I Chu
High-order-harmonic generation (HHG) is produced by the interaction of atoms or molecules with strong laser fields, leading to the emission of extreme ultraviolet (XUV) photons. Its potential application (1–6) as an attosecond light source has attracted much interest in ultrafast science and technology. The attosecond pulse generation provides an important tool to probe and control the dynamical behaviours of atoms, molecules, and condensed matter (7–9). The essential features in HHG, such as a rapid drop at low-order harmonics, above-threshold harmonic plateau, and finally a sharp cutoff beyond which no further harmonic emission, have been observed experimentally. The HHG cutoff is estimated approximately at the energy Ip+3.17Up, where Ip is the atomic ionization potential, and Up is the ponderomotive energy. The HHG process can be well understood by a semiclassical three-step model (10,11). Firstly, the bound electron tunnels through the barrier formed by the Coulomb potential and the laser field, then it is subsequently accelerated and obtain the kinetic energy from the laser field. Finally, the electrons can be driven back toward the core and recombine with the ground state to convert the binding energy and kinetic energy into an emitted harmonic photon. For most of the study of the HHG, the major attention has been focused on the first rescattering in HHG. However, the multiple rescattering processes also play an important role in HHG and the dynamical origin of the HHG associated with multiple rescattering is less understood and largely unexplored.
Generation of intense single short attosecond pulse with a multicycle spatially inhomogeneous field
Published in Journal of Modern Optics, 2021
Gangtai Zhang, Ziqi Wang, Tingting Bai, Rui Gao, Shangbin Jiao, Haiyan Ma, Yueqiang Hu, Yuefeng Han, Yifan Shang, Xi Zhao
Next, we consider the production of the single attosecond puls. As a comparison, we also give the temporal profile of the attosecond pulse in the two-color homogeneous field. As seen from Figure 4(a), by synthesizing the harmonics in the range from the 101st to 117th orders, two dominating attosecond pulses are produced, and the corresponding pulse durations are 143 and 118 as, respectively. This is because each order harmonic for the supercontinuum primarily stems from two quantum paths with different emission times. Among them, the strong 143 as pulse derives from the short path, the weak 118 as pulse originates from the long one, which is in good accord with the analysis of the time-frequency diagram. Such an attosecond pulse limits its potential application in practice. Figure 4(b) shows the temporal profile of the generated attosecond pulse in the two-color inhomogeneous field. By superposing the optimal harmonics from the 930th to 1120th orders around the cutoff region, a pure single 15.2 as pulse is directly produced without any phase compensation. This is in sharp contrast to Figure 4(a), in which two attosecond pulses are emitted at the same time. Such a short single attosecond pulse will allow one to probe and manipulate the electronic dynamics inside atoms and molecules with an unprecedented precision. Our further calculations confirm that similar single attosecond pulses indicated in Figure 4(b) can be obtained by straightforwardly filtering some well-selected harmonics in the continuous spectrum region. Figure 4(c) presents the temporal profiles of the isolated attosecond pulses synthesized by the harmonics of 860th-1030th, 880th-1070th, 900th-1090th, and 920th-1105th, respectively. Obviously, the duration of the generated single short attosecond pulse is 15.2 as and only the pulse intensity decreases a little bit, which is a better support for our standpoint. Moreover, a serial of single attosecond pulses with the duration of less than 24 as can be directly achieved via superimposing a random 110-order harmonics in the range of 685th to 1135th order. To make this judgement, we study the single attosecond pulse generation for this case. As shown in Figure 4(d), by synthesizing the harmonics of 685th-795th, 800th-910th, 910th-1020th, and 1025th-1035th, single attosecond pulses with clean temporal profiles are directly generated, and the corresponding durations are 20.5, 23.4, 22.4, and 22.1 as, respectively. This characteristic may provide a convenience method for generating a single sub-24 as pulse with a tunable central wavelength in experiment.