Effect of electron correlation on high-order harmonic generation in helium model atom

We investigate high-order harmonic generation (HHG) of Li + ion driven by an intense infrared (IR) laser field in combination with a weak XUV pulse. To achieve this, we first construct an accurate single-active electron angular-momentumdependent model potential of Li + ion, by which the accurate singlet energy levels of Li + for the ground state and excited states with higher quantum numbers can be obtained. Then, we solve numerically the three dimensional time-dependent Schrödinger equation of Li + ion by means of the generalized pseudospectral method to obtain HHG. Our results show that the strength of assisted XUV is not amplified during the harmonic generation process, but the yield of HHG power spectrum in the whole plateau has a significant enhancement. Furthermore, the optimal phase delay between the IR and XUV pulses allows the production of ultrabroadband supercontinuum spectra. By superposing some harmonics, a strong new single 27-attosecond ultrashort pulse can be obtained.

Section: Hhg Of LI + In the Combined Laser Fieldmentioning

confidence: 99%

High-order harmonic generation of Li ⁺ with combined infrared and extreme ultraviolet fields

Wang

Jiao

et al. 2018

“…[18,19] Recently, Luo et al [20] have shown dramatic cutoff extension and broadband supercontinuum generation in multi-cycle two-color pulses, which can directly generate an isolated sub-100-as pulse. Hu et al [21] proposed effect of electron correlation on high-order harmonic generation of He model atom. Li et al [22] theoreti-cally achieved an isolated 26-as pulse of He + by means of an intense few-cycle chirped laser field.…”

Section: Introductionmentioning

confidence: 99%

Quantum path control and isolated attosecond pulse generation in the combination of near-infrared and terahertz pulses

Zhong¹,

Guo²,

Zhang³

et al. 2015

We present an efficient and realizable scheme for the generation of an ultrashort single attosecond (as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz (THz) field. The high-order harmonic generation (HHG) can be obtained by solving the time-dependent Schrödinger equation accurately and efficiently with time-dependent generalized pseudo-spectral (TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time–frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained.

“…[1] In these applications, how to effectively extract the harmonic signal from the mixed signal which is interfered by chaotic signal has very important theoretic and practical significance. [2,3] Leung et al [4] estimated the harmonic signal amplitude and frequency in chaotic interference background by the minimum phase space volume method. Haykin and Li [5] studied the small target signal extraction from sea clutter signal with chaotic characteristic by artificial neural network.…”

Section: Introductionmentioning

confidence: 99%

Harmonic signal extraction from noisy chaotic interferencebased on synchrosqueezed wavelet transform

Wang

2015

For the harmonic signal extraction from chaotic interference, a harmonic signal extraction method is proposed based on synchrosqueezed wavelet transform (SWT). First, the mixed signal of chaotic signal, harmonic signal, and noise is decomposed into a series of intrinsic mode-type functions by synchrosqueezed wavelet transform (SWT) then the instantaneous frequency of intrinsic mode-type functions is analyzed by using of Hilbert transform, and the harmonic extraction is realized. In experiments of harmonic signal extraction, the Duffing and Lorenz chaotic signals are selected as interference signal, and the mixed signal of chaotic signal and harmonic signal is added by Gauss white noises of different intensities. The experimental results show that when the white noise intensity is in a certain range, the extracting harmonic signals measured by the proposed SWT method have higher precision, the harmonic signal extraction effect is obviously superior to the classical empirical mode decomposition method.