Bayesian approach for the optimal control of high-order harmonics for the generation of ultrashort attosecond laser pulses

2021 ◽  
Author(s):  
Wei-Teng Wang ◽  
Yae-Lin Sheu ◽  
Shih-I Chu
Keyword(s):  
Laser Pulse ◽  
Laser Field ◽  
Pseudospectral Method ◽  
Laser Pulses ◽  
Optimization Method ◽  
High Order ◽  
Time Dependent ◽  
Bayesian Optimization ◽  
Time Frequency ◽  
Isolated Attosecond Pulse

Abstract We present an efficient and powerful method to optimize the production of high-order harmonic generation (HHG) and ultrashort single attosecond laser pulses. The system under investigation is the helium atoms that are exposed to the combination of chirped two-color mid-IR laser field and its 34th harmonic. The time-dependent Schrödinger equation is solved accurately and efficiently by means of the time-dependent generalized pseudospectral method and the time-frequency spectrum is obtained by the wavelet transform. We extend the machine-learning based optimization method, called Bayesian optimization (BO), to optimize the incident laser pulse to generate ultrashort attosecond laser pulse successfully for the first time. It is shown that the intensity of HHG power spectrum from the plateau region to the cutoff is enhanced by the optimized laser field by several orders of magnitude. Further, an ultrafast isolated attosecond pulse of 10 attosecond can be generated efficiently by superposing the plateau harmonics.

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.

scholarly journals Extension of harmonic cut-off in a waveform controlled laser field by prolonging the recombining period

2010 ◽  
Vol 28 (3) ◽  
pp. 415-419 ◽  
Author(s):  
Junjie Xu ◽  
Yongli Yu ◽  
Bin Zeng
Keyword(s):  
Laser Field ◽  
Extreme Ultraviolet ◽  
High Energy ◽  
Fundamental Wave ◽  
Half Cycle ◽  
Time Frequency ◽  
High Order Harmonic ◽  
High Energy Electrons ◽  
Isolated Attosecond Pulse ◽  
Harmonic Conversion

AbstractWe present a novel waveform synthesized by a half-cycle fundamental wave (800 nm) and a half-cycle subharmonic wave (2400 nm) with an appropriate carrier-envelope phase and a phase delay, in which more ionized electrons can recombine with its parent ions to emit high-order harmonic, giving rise to both the extension of the extreme ultraviolet supercontinuum and the enhancement of harmonic conversion efficiency. An isolated attosecond pulse with considerable energy is obtained as well. By performing time-frequency analyses, it is revealed that the prolonged opposite electric field increases the recombining probability of high-energy electrons.

scholarly journals Macroscopic effects of high-order harmonic and isolated attosecond pulse generation driven by two-color laser field

2011 ◽  
Vol 60 (10) ◽  
pp. 103202
Author(s):  
Lu Ying-Ying ◽  
Zeng Zhi-Nan ◽  
Zheng Ying-Hui ◽  
Zou Pu ◽  
Liu Can-Dong ◽  
...  
Keyword(s):  
Laser Field ◽  
Pulse Generation ◽  
Attosecond Pulse ◽  
High Order ◽  
High Order Harmonic ◽  
Isolated Attosecond Pulse ◽  
Attosecond Pulse Generation

Recurring Molecular Alignment Induced by Pulsed Nonresonant Laser Fields

2001 ◽  
Vol 66 (7) ◽  
pp. 991-1004 ◽  
Author(s):  
Long Cai ◽  
Břetislav Friedrich
Keyword(s):  
Laser Pulse ◽  
Laser Field ◽  
Analytic Solution ◽  
Short Pulse ◽  
Molecular Alignment ◽  
Time Dependent ◽  
Molecular Axis ◽  
Linear Molecule ◽  
Numerical Computations ◽  
Laser Fields

We examine the rotational wavepackets created by the nonadiabatic interaction of a linear molecule with a pulsed nonresonant laser field. We map out the recurrences of the wavepackets and of the concomitant alignment as a function of the duration and intensity of the laser pulse. We derive an analytic solution to the time-dependent Schrödinger equation in the short-pulse limit and find it to agree quantitatively with our numerical computations. This indicates that the recurrences are favored under an impulsive transfer of action from the radiative field to the molecule. The recurring wavepackets afford field-free alignment of the molecular axis.

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