- 标题
- 摘要
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- 实验方案
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Characterizing the ellipticity of an isolated attosecond pulse
摘要： We propose and theoretically demonstrate a single-shot measurement method to measure the ellipticity of an isolated attosecond pulse (IAP). By solving the time-dependent Schr?dinger equation, we calculate the photoelectron momentum distributions (PMDs) from strong field ionization of argon in an arbitrary polarized IAP streaked with a linearly polarized infrared pulse. It is shown that the ellipticity of the IAP is encoded in the PMDs. A linear relation between the angular shift of the three main lobes of the PMDs and the ellipticity of the IAP is obtained, which provides an efficient and robust way for characterizing the ellipticity of the IAP.
关键词： Photoelectron momentum distribution,Attosecond pulse,Elliptically polarized
更新于2025-09-23 15:23:52
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Enhancement of attosecond pulse in water window region by using pump-probe approach
摘要： An effective scheme to enhance the harmonic yield and the attosecond (as) pulse signal from H+2 has been proposed by using the pump-probe laser field. It is found that with the help of the multi-cycle pump pulse, H+2 can be steered into the resonance ionization regions, where the ionization probability can be remarkably enhanced. Thus, the harmonic yield can be remarkably enhanced when a sequential mid-infrared probe pulse is added. Further, by modulating the phase of the probe pulse and by adding a controlling pulse, the harmonic cutoff can be extended up to the water window region. Finally, by the Fourier transformation of the selected harmonics on the harmonic supercontinuum, the water window attosecond pulses as short as 25 as can be obtained.
关键词： High-order harmonic generation,pump-probe pulse,charge resonance enhanced ionization,single attosecond pulse,harmonic enhancement
更新于2025-09-23 15:21:21
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Intense circularly polarized attosecond pulse generation from solid targets irradiated with a two-color linearly polarized laser
摘要： A method for the production of intense circularly polarized (CP) attosecond pulses from relativistic laser-solid interactions is proposed, where a two-color linearly polarized (LP) laser is used. The polarization, photon frequency, and other properties of the obtained attosecond pulse can be controlled by adjusting the ratio of the dichromatic driving LP field in different harmonics, which is much easier and more efficient than those previously using CP driving lasers. Both one- and two-dimensional particle-in-cell simulations show that a CP attosecond extreme-ultraviolet pulse with an intensity of 1.4 × 1019 W/cm2 and a duration of about 120 as is obtained by a two-color LP laser at intensities in the fundamental and second harmonics of, respectively, 1.5 × 1022 and 6.4 × 1021 W/cm2, which can be applied for the detection of the magnetic and chiral properties of materials.
关键词： relativistic laser-solid interactions,attosecond pulse,two-color linearly polarized laser,circularly polarized,extreme-ultraviolet pulse
更新于2025-09-23 15:21:01
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Effects of inhomogeneous laser field in time and space on the generation of broad spectral continuum and ultrashort attosecond pulse
摘要： The inhomogeneous effects of laser field in time and space on the generations of high-order harmonic spectra and attosecond pulses from He atom have been investigated with the assistance of the frequency-chirping technique and the metallic nanostructure. We find that in different combinations of chirps and spatial inhomogeneous effects, not only can the harmonic cutoff be extended, but the single harmonic emission peak (HEP) can also be selected to contribute to the spectral continuum. In detail, with the combinations of (i) symmetric chirp in frequency and positive inhomogeneous effect in space or (ii) asymmetric down chirp in frequency and negative inhomogeneous effect in space, two broad spectral continua with bandwidths of 496 eV and 480 eV can be obtained. Further, by properly adding IR or UV controlling pulse, the harmonic emission efficiency can be enhanced by several orders of magnitude. The enhancement of harmonic yield from adding UV pulse is higher than that from adding IR pulse. Moreover, the difference of harmonic enhancement between UV combined field and IR combined field is much more obvious at lower controlling laser intensity. Through analyzing the ionization probability, we find that the higher enhancement of harmonic yield from UV combined field is because of UV-resonance-enhancement-ionization between the ground state and the excited state of He atom. Finally, by properly superposing some harmonics, a number of attosecond pulses with pulse durations of 45 as can be obtained.
关键词： frequency-chirping technique,High-order harmonic generation,two-color field,inhomogeneous effect in space,ultrashort attosecond pulse
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Cavity-Enhanced Noncollinear High-Harmonic Generation
摘要： The generation of extreme-ultraviolet (XUV) attosecond pulse trains (APTs) by the process of high harmonic generation (HHG) has enabled the investigation of electronic dynamics in atoms, molecules and solids. Enhancing the pulse energy impinging on the target gas by usually one to two orders of magnitude by means of an external, passive resonator (enhancement cavity, EC) permits efficient HHG at repetition rates exceeding 10 MHz, enabling applications in XUV precision spectroscopy and space-charge-limited regimes of photoelectron or coincidence spectroscopy.
关键词： attosecond pulse trains,high harmonic generation,extreme-ultraviolet,XUV precision spectroscopy,enhancement cavity
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Polarization-Resolved High Harmonic Spectroscopy of Interlocked Attosecond Bursts
摘要： High-harmonic spectroscopy is an important tool for investigation of nonlinear atom-laser interaction. Polarization-resolved high harmonic spectroscopy is becoming a promising method for exploring chiral quantities, in particular as numerous techniques have been demonstrated experimentally for generating bright and applicable high-order harmonics with highly helical polarization. In this context, a simple direct mapping (ideally, analytical formula) between the harmonics polarization and time-domain description of the HHG process would be very useful. Here, we present an analytic mapping between ellipticities of the high harmonics and variables of an interlocked pair of attosecond pulse trains - relative emission directions, relative delay, and their ellipticities – in a new scheme for generation of bright helically polarized high harmonics. In this scheme, HHG is driven by a two-color pulse, a fundamental frequency and its second harmonic, where the two colors are slightly elliptically polarized with opposite helicity and perpendicular ellipse major axes. In the time domain, the HHG emission consists of a pair of nearly linearly polarized attosecond pulse trains (APTs), yet with very different polarization axes. The ellipticities of the harmonics vary from linear to circular by tweaking the ellipticity of the pump. We discovered that the underlying mechanism for this ultra-sensitive polarization knob is dominantly induced by phase shifts between the pair of interlocked APTs. The ellipticity of the attosecond bursts and their relative emission angles play a secondary, yet still easily measured, role. Obtaining an analytic formula for the ellipticities of the high harmonics as a function of the APTs variables allow us to probe the APTs by ellipticity-resolved high harmonic spectroscopy. We demonstrate this approach experimentally.
关键词： High-harmonic spectroscopy,attosecond pulse trains,helical polarization,polarization-resolved,two-color pulse
更新于2025-09-12 10:27:22
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Attosecond Pulse Amplification in a Plasma-Based X-Ray Laser Dressed by an Infrared Laser Field
摘要： High-harmonic generation (HHG) of laser radiation has led to attosecond pulse formation which offers unprecedented temporal resolution in observing and controlling electron and nuclear dynamics. But the energy of attosecond pulses remains quite small, especially for photon energies exceeding 100 eV, which limits their practical applications. We propose a method for amplification of attosecond pulses in the active medium of a plasma-based x-ray laser dressed by a replica of the laser field used for HHG. The experimental implementation is suggested in hydrogenlike C5t x-ray laser at 3.4 nm wavelength in the “water window” range.
关键词： attosecond pulse amplification,infrared laser field,plasma-based x-ray laser,high-harmonic generation,water window
更新于2025-09-12 10:27:22
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Attosecond pulse generation by relativistic flying mirrors in laser-plasma interaction: Effect of plasma density and driver amplitude on the generated pulse
摘要： The generation of high-intensity attosecond pulses by the interaction of two counterpropagating short laser pulses with underdense plasma is investigated. By using parallel fully kinetic particles in cell simulation, which shows the formation of relativistic ?ying mirrors in the wake wave of the intense driver laser pulse and the focusing re?ection of the weak source pulse, it is demonstrated that intense attosecond pulses can be produced under the optimized conditions of plasma density and driver laser amplitude according to the relativistic similarity theory. In addition, it is shown that the frequency of the source pulse is upshifted by a factor from 10 to 80 corresponding to a re?ected radiation wavelength from 20 to 164 nm which lies in the extreme ultraviolet region, while most of the energy lies around a frequency upshift of 20, in agreement with the measured Lorentz factor. The intensity of the main attosecond pulse is two orders higher than the source pulse intensity.
关键词： plasma density,driver amplitude,attosecond pulse generation,relativistic flying mirrors,laser-plasma interaction
更新于2025-09-12 10:27:22
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Role of quantum orbits in odd-even high harmonic generation from atoms in bichromatic laser fields
摘要： We study high-order harmonic generation from atoms in bichromatic laser fields numerically and analytically. With the weak increase of the second harmonic field, the calculated odd and even HHG spectra differ remarkably from each other in some energy regions. Our analyses reveal that the interference of two neighboring quantum orbits plays an important role in this phenomenon. In particular, we show that with a trajectory-resolved approach, the emission of odd or even harmonics can be effectively controlled in a wide HHG energy region. Our results suggest a potential approach for generating even-harmonic-dominating attosecond pulse.
关键词： odd-even harmonics,bichromatic laser fields,attosecond pulse,quantum orbits,high-order harmonic generation
更新于2025-09-11 14:15:04
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Controlling polarization of high-order harmonic generation by molecular alignment in a bicircular laser field
摘要： The polarization of high-order harmonic generation in H2+ driven by a counterrotating bichromatic ω/3ω circularly polarized laser field is investigated theoretically. The elliptically polarized harmonics are characterized by ellipticity and rotation angle, where the latter is expanded to [?π /2, π /2] by an optimized definition. We find a critical alignment angle where the ellipticity of high-energy harmonics is almost the same, so an attosecond pulse train with a high degree of polarization can be synthesized. In addition, we find that the rotation angle is always different from the alignment angle by 90? with a small deflection. Thus, we propose a scheme to control the harmonic polarization state by the molecular alignment angle.
关键词： molecular alignment,attosecond pulse,high-order harmonic generation,polarization,bicircular laser field
更新于2025-09-11 14:15:04