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.

Water window attosecond sources generation by using the multi-cycle time-delay two circularly polarized pulses

2015 ◽  
Vol 29 (23) ◽  
pp. 1550170 ◽  
Author(s):  
Li-Qiang Feng ◽  
Hang Liu
Keyword(s):  
Time Delay ◽  
Cycle Time ◽  
Delay Time ◽  
Harmonic Spectrum ◽  
High Order ◽  
Circularly Polarized ◽  
Water Window ◽  
Attosecond Pulses ◽  
Window Region ◽  
Whole Water

In this paper, a promising scheme is proposed to generate the water window isolated attosecond pulses from the high-order harmonics by using the multi-cycle time-delay two circularly polarized pulses. The results show that with the introduction of delay time of the two pulses, not only the harmonic cutoff is extended, but also the modulation on the harmonic spectrum is suppressed. Especially for the [Formula: see text] nm, [Formula: see text] nm and the [Formula: see text] nm two cases, a 341 eV and a 502 eV supercontinua including the whole water window region are obtained. Finally, by properly superposing the harmonics in the supercontinua regions, a series of sub-34as wavelength-tunable attosecond pulses in 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.

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.

scholarly journals Atomic and Molecular Processes in a Strong Bicircular Laser Field

Atoms ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 61 ◽  
Author(s):  
Dejan Milošević
Keyword(s):  
Laser Field ◽  
Ultrashort Pulses ◽  
High Order ◽  
Molecular Processes ◽  
Threshold Ionization ◽  
High Order Harmonic ◽  
Above Threshold Ionization ◽  
Wide Range ◽  
Linearly Polarized ◽  
Atomic And Molecular Processes

With the development of intense femtosecond laser sources it has become possible to study atomic and molecular processes on their own subfemtosecond time scale. Table-top setups are available that generate intense coherent radiation in the extreme ultraviolet and soft-X-ray regime which have various applications in strong-field physics and attoscience. More recently, the emphasis is moving from the generation of linearly polarized pulses using a linearly polarized driving field to the generation of more complicated elliptically polarized polychromatic ultrashort pulses. The transverse electromagnetic field oscillates in a plane perpendicular to its propagation direction. Therefore, the two dimensions of field polarization plane are available for manipulation and tailoring of these ultrashort pulses. We present a field that allows such a tailoring, the so-called bicircular field. This field is the superposition of two circularly polarized fields with different frequencies that rotate in the same plane in opposite directions. We present results for two processes in a bicircular field: High-order harmonic generation and above-threshold ionization. For a wide range of laser field intensities, we compare high-order harmonic spectra generated by bicircular fields with the spectra generated by a linearly polarized laser field. We also investigate a possibility of introducing spin into attoscience with spin-polarized electrons produced in high-order above-threshold ionization by a bicircular field.

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.

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.

THE SOME QUESTIONS OF AUTONOMOUS MOTION AND MANAGEMENT OF LAND-MOBILE ROBOTIC COMPLEXES FOR UKRAINIAN GROUND FORCESE

2019 ◽  
pp. 53-58
Author(s):  
О. Кravchuk ◽  
V. Symonenkov ◽  
I. Symonenkova ◽  
O. Hryhorev
Keyword(s):  
Large Scale ◽  
Armed Forces ◽  
Distributed Information ◽  
Wide Range ◽  
Highly Effective ◽  
Information Management Systems ◽  
Robotic Devices ◽  
Principles And Standards ◽  
And Control ◽  
The Eu

Today, more than forty countries of the world are engaged in the development of military-purpose robots. A number of unique mobile robots with a wide range of capabilities are already being used by combat and intelligence units of the Armed forces of the developed world countries to conduct battlefield intelligence and support tactical groups. At present, the issue of using the latest information technology in the field of military robotics is thoroughly investigated, and the creation of highly effective information management systems in the land-mobile robotic complexes has acquired a new phase associated with the use of distributed information and sensory systems and consists in the transition from application of separate sensors and devices to the construction of modular information subsystems, which provide the availability of various data sources and complex methods of information processing. The purpose of the article is to investigate the ways to increase the autonomy of the land-mobile robotic complexes using in a non-deterministic conditions of modern combat. Relevance of researches is connected with the necessity of creation of highly effective information and control systems in the perspective robotic means for the needs of Land Forces of Ukraine. The development of the Armed Forces of Ukraine management system based on the criteria adopted by the EU and NATO member states is one of the main directions of increasing the effectiveness of the use of forces (forces), which involves achieving the principles and standards necessary for Ukraine to become a member of the EU and NATO. The inherent features of achieving these criteria will be the transition to a reduction of tasks of the combined-arms units and the large-scale use of high-precision weapons and land remote-controlled robotic devices. According to the views of the leading specialists in the field of robotics, the automation of information subsystems and components of the land-mobile robotic complexes can increase safety, reliability, error-tolerance and the effectiveness of the use of robotic means by standardizing the necessary actions with minimal human intervention, that is, a significant increase in the autonomy of the land-mobile robotic complexes for the needs of Land Forces of Ukraine.

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