Generation of water window single attosecond pulse from multi-cycle mid-infrared laser field with chirp gating modulation

2019 ◽  
Vol 33 (06) ◽  
pp. 1950064 ◽  
Author(s):  
Hang Liu ◽  
Henry M. Schafer ◽  
R. L. Q. Feng ◽  
A. Yuanzi Feng
Keyword(s):  
Pulse Duration ◽  
Laser Field ◽  
Initial State ◽  
Mid Infrared ◽  
Water Window ◽  
High Order Harmonic ◽  
Chirp Modulation ◽  
Window Region ◽  
Gating Modulation ◽  
Cycle Pulse

A potential scheme to produce the water window single attosecond pulses (SAPs) from the multi-cycle mid-infrared (MIR) laser field has been investigated with the help of the chirp gating modulation. It is found that with the introduction of the laser chirp (i.e. up-chirp or down-chirp modulation), the extension of the harmonic cutoff can be achieved and the single harmonic radiation peak (HRP) can be selected during the harmonic emission process. Moreover, the chirp gating modulation on the high-order harmonic generation (HHG) is sensitive to the few-cycle pulse duration, but it is not very sensitive to the multi-cycle pulse duration. Moreover, a larger extension of the harmonic cutoff covering the whole water window region can be found with the help of the multi-cycle down-chirp modulation. Further, by properly choosing the coherent superposition of the ground state and the high Rydberg state as the initial state, the efficiency of HHG can be enhanced by 5 orders of magnitude. Finally, a series of high-intensity sub-40as pulses covering the water window region can be obtained.

Improvement of High-Order Harmonic Generation Via Controlling Multiple Acceleration–Recombination Process

2019 ◽  
Vol 74 (7) ◽  
pp. 561-571 ◽  
Author(s):  
Yi Li ◽  
Li-Qiang Feng ◽  
Yan Qiao
Keyword(s):  
Harmonic Generation ◽  
Laser Field ◽  
High Order ◽  
Recombination Process ◽  
Half Cycle ◽  
High Order Harmonic Generation ◽  
Water Window ◽  
High Order Harmonic ◽  
Window Region ◽  
Frequency Chirping

AbstractThe multiple acceleration–recombination process in high-order harmonic generation (HHG) has been investigated and discussed. Generally, the HHG can be explained through the ionization–acceleration–recombination process in each half-cycle waveform of the laser field. In this article, through the waveform control via the two-colour frequency-chirping laser field, the multiple acceleration–recombination process of the free electron in a specific “W” waveform structure can be found, which will lead to the larger emitted photon energies. Moreover, with the optimization of this “W” waveform by changing the frequency chirps, the carrier envelope phases, and the delay time, not only the efficiency of HHG can be enhanced compared with that from the original chirp-free pulse, but also the larger harmonic cutoff can be obtained. Further, with the assistance of the unipolar pulses, the cutoff and the efficiency of HHG can be further improved, showing a water window spectral continuum with the intensity enhancement of 66 times. As a result, by properly superposing some selected harmonics on the spectral continuum, three intense 38-as pulses in the water window region can be obtained.

scholarly journals Towards GW-Scale Isolated Attosecond Pulse Far beyond Carbon K-Edge Driven by Mid-Infrared Waveform Synthesizer

2018 ◽  
Vol 8 (12) ◽  
pp. 2451 ◽  
Author(s):  
Yuxi Fu ◽  
Hua Yuan ◽  
Katsumi Midorikawa ◽  
Pengfei Lan ◽  
Eiji Takahashi
Keyword(s):  
Single Cycle ◽  
High Order Harmonic Generation ◽  
Mid Infrared ◽  
X Ray ◽  
Water Window ◽  
High Order Harmonic ◽  
Optical Parametric ◽  
Isolated Attosecond Pulse ◽  
Window Region ◽  
The Continuum

We discuss the efficient generation of intense “water window” (0.28–0.54 keV) isolated attosecond pulses (IAPs) using a mid-infrared (MIR) waveform synthesizer. Our numerical simulations clearly indicate that not only a longer-wavelength driving laser but also a weak control pulse in the waveform synthesizer helps extend the continuum cutoff region and reduce the temporal chirp of IAPs in high-order harmonic generation (HHG). This insight indicates that a single-cycle laser field is not an optimum waveform for generating the shortest IAP from the veiwpoints of reducing the attochirp and increasing the efficiency of HHG. By combining a waveform synthesizer technology and a 100 mJ MIR femtosecond pulse based on a dual-chirped optical parametric amplification (DC-OPA) method, a gigawatt-scale IAP (55 as with 10 nJ order) in the water window region can be generated even without attochirp compensation. The MIR waveform synthesizer is highly beneficial for generating a shorter IAP duration in the soft X-ray region because there are no suitable transparent dispersive materials that can be used for compressing the attochirp.

Selection and Enhancement of the Single Harmonic Emission Event in the Water Window Region

2018 ◽  
Vol 73 (11) ◽  
pp. 985-994 ◽  
Author(s):  
Hang Liu ◽  
A. Yuanzi Feng
Keyword(s):  
Fourier Transformation ◽  
Half Cycle ◽  
Laser Polarization ◽  
High Order Harmonic Generation ◽  
Harmonic Emission ◽  
Water Window ◽  
Polarization Gating ◽  
High Order Harmonic ◽  
Window Region ◽  
Cycle Pulse

AbstractThe control of the high-order harmonic generation in the half-cycle region has been investigated by using the improved polarization gating (PG) technology. It is found that by properly controlling the delay time of the PG pulse, the contribution of the harmonic plateau is nearly coming from the single harmonic emission event, which is much better for producing the single attosecond pulses (SAPs). Further, by properly adding an ultraviolet pulse and a half-cycle pulse in the driven laser polarization direction, the harmonic yield can be enhanced and the harmonic cutoff can be extended, showing a high-intensity harmonic plateau covering the whole water window region. Finally, through the Fourier transformation of some selected harmonics, a 35 as SAP in the water window region can be obtained.

scholarly journals Control of the polarization direction of isolated attosecond pulses using inhomogeneous two-color fields

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Stephen Maina Njoroge ◽  
Hua Yuan ◽  
Kinyua Dickson ◽  
Qingbin Zhang ◽  
Pengfei Lan
Keyword(s):  
Polarization Direction ◽  
Relative Angle ◽  
Water Window ◽  
High Order Harmonic ◽  
Fundamental Pulse ◽  
Wide Range ◽  
Attosecond Pulses ◽  
Linearly Polarized ◽  
Window Region ◽  
And Control

AbstractWe theoretically demonstrate the control of the polarization direction of isolated attosecond pulses (IAPs) with inhomogeneous two-color fields synthesized by an 800-nm fundamental pulse and a 2000-nm control pulse having crossed linear polarizations. The results show that by using the temporally and spatially shaped field, the high-order harmonic generation (HHG) process can be efficiently controlled. An ultra-broad supercontinuum ranging from 150th to 400th harmonics which covers the water window region is generated. Such a supercontinuum supports the generation of a 64-as linearly polarized IAP, whose polarization direction is at about 45° with respect to the x axis. Moreover, we analyze the influence of the inhomogeneity parameters and the relative angle of the fundamental and control pulses on the IAP generation. It is shown that the polarization direction of the IAP can rotate in a wide range approximately from 8° to 90° relative to the x axis when the inhomogeneity parameters and the relative angle vary.

High-order harmonic generation with a single-color mid-infrared laser field by frequency-chirping

2019 ◽  
Vol 33 (13) ◽  
pp. 1950122 ◽  
Author(s):  
Yunhui Wang ◽  
Dandan Song ◽  
Qiang Zuo ◽  
Hong Wu ◽  
Zhihong Yang
Keyword(s):  
Harmonic Generation ◽  
Laser Field ◽  
Infrared Laser ◽  
Pulse Generation ◽  
High Order ◽  
Time Dependent ◽  
Mid Infrared ◽  
High Order Harmonic ◽  
Isolated Attosecond Pulse ◽  
Frequency Chirping

By numerically solving the time-dependent Schrödinger equation for helium atoms in a single mid-infrared laser field, we explore the frequency-chirping effect of laser field on high-order harmonic and isolated attosecond pulse generation. One or two ultrabroad supercontinuum harmonic plateaus can be controlled through modulating the laser field frequency by a small time-dependent signal. Under the best chirping condition, an ultrashort 2.2 as pulse can be obtained by Fourier transformation with the bandwidth of 782 eV. Furthermore, we explain the harmonic generation physical mechanisms by classical ionizing and returning energy maps and time–frequency analyzes.

Generation of a coherent x ray in the water window region at 1 kHz repetition rate using a mid-infrared pump source

2009 ◽  
Vol 34 (11) ◽  
pp. 1747 ◽  
Author(s):  
Hui Xiong ◽  
Han Xu ◽  
Yuxi Fu ◽  
Jinping Yao ◽  
Bin Zeng ◽  
...  
Keyword(s):  
Repetition Rate ◽  
Mid Infrared ◽  
X Ray ◽  
Water Window ◽  
Pump Source ◽  
Window Region

Selection of intense spectral region and attosecond pulse from X2+ by using chirp-delay effect

2020 ◽  
Vol 34 (09) ◽  
pp. 2050083
Author(s):  
Hui Liu ◽  
Hang Liu ◽  
Cheryl Ford
Keyword(s):  
Pulse Duration ◽  
Laser Field ◽  
Fourier Transformation ◽  
Emission Peak ◽  
Main Role ◽  
Half Cycle ◽  
Delay Effect ◽  
Cycle Pulse ◽  
Selection Of ◽  
Specific Timing

A potential scheme to obtain intense harmonic spectra from X[Formula: see text] ([Formula: see text] and T) has been studied by using chirped-delay effect and half-cycle pulse. First, for the shorter pulse duration case, the main contributions of harmonic spectra of H[Formula: see text] and T[Formula: see text] are both coming from the falling part of laser field. While, for the longer pulse duration case, the rising and falling parts of laser field play the main role in harmonic spectra of H[Formula: see text] and T[Formula: see text], respectively. Second, according to the changed law of harmonic yields of H[Formula: see text] and T[Formula: see text] and by properly introducing the chirp-delay effect at some specific timing, the intense harmonic emission peak (HEP) can be obtained from both H[Formula: see text] and T[Formula: see text]. Third, with the help of the half-cycle pulse, the selected HEP can be further extended, showing the intense and broad spectral continua. Finally, by Fourier transformation of some harmonics on the spectral continua, the intense attosecond pulses with durations of 35 as can be produced.

Waveform control in generations of intense water window attosecond pulses via multi-color combined field

2019 ◽  
Vol 33 (13) ◽  
pp. 1950130 ◽  
Author(s):  
Liang Li ◽  
Mian Zheng ◽  
R. Liqiang Feng ◽  
Yan Qiao
Keyword(s):  
Half Cycle ◽  
High Order Harmonic Generation ◽  
Initial State ◽  
Water Window ◽  
The Third ◽  
High Order Harmonic ◽  
Waveform Control ◽  
Attosecond Pulses ◽  
Color Field ◽  
Selective Enhancement

The waveform control in the improvements of high-order harmonic generation (HHG) spectra and attosecond pulse signals driven by the two-color and three-color combined fields has been theoretically investigated. (a) The results show that by properly controlling the [Formula: see text]–2[Formula: see text] two-color laser beam (including the modulations of chirps, carrier envelope phases and delay time), either the harmonic cutoff can be extended, showing a water window spectral continuum, or the selective enhancement of the single-order and two-order harmonics can be found. Further, with the introduction of a third controlling field, the efficiency of spectral continuum can be enhanced by two orders of magnitude compared with that from the two-color field. Moreover, the enhancement of HHG is not very sensitive to the frequency of the third field (i.e., the frequency of the third field is chosen to be 3[Formula: see text], 4[Formula: see text] and 6[Formula: see text]). Thus, some water window attosecond pulses with the durations of 60 as can be obtained. (b) Furthermore, the harmonic cutoff can be further extended when using a half-cycle controlling pulse or introducing the inhomogeneous effect of the laser field. Moreover, the efficiency of HHG can be further improved when the initial state is prepared as the superposition state of the ground state and some excited state of He atom. Consequently, a much broader spectral continuum with an intensity enhancement of another two orders of magnitude can be found. Finally, through the Fourier transformation of some spectral continuum, the intense water window attosecond pulses with the durations of 60 as can be produced.

Enhancement of attosecond pulse in water window region by using pump-probe approach

2018 ◽  
Vol 32 (29) ◽  
pp. 1850318 ◽  
Author(s):  
Hang Liu ◽  
Yi Li ◽  
Rich S. Castle
Keyword(s):  
Probe Pulse ◽  
Fourier Transformation ◽  
Pulse Signal ◽  
Ionization Probability ◽  
Probe Laser ◽  
Resonance Ionization ◽  
Pump Probe ◽  
Mid Infrared ◽  
Water Window ◽  
Window Region

An effective scheme to enhance the harmonic yield and the attosecond (as) pulse signal from H[Formula: see text] has been proposed by using the pump-probe laser field. It is found that with the help of the multi-cycle pump pulse, H[Formula: see text] 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.

Sign in / Sign up

Export Citation Format

Share Document