Semi-integer harmonic generation from an argon atom by bichromatic counter-rotating circularly polarized laser field*

Self Cite

We investigate the ellipticity of the high-order harmonic generation from the oriented $\textrm{H}_{2}^{+}$ exposed to a linearly polarized laser field by numerically solving the two dimensional time-dependent Schr$\ddot{\textrm{o}}$dinger equation (2D TDSE). Numerical simulations show that the harmonic ellipticity is remarkably sensitive to the alignment angle. The harmonic spectrum is highly elliptically polarized at a specific alignment angle $\theta = 30^\circ $, which is insensitive to the variation of the laser parameters. The position of the harmonic intensity minima indicates the high ellipticity, which can be attributed to the two-center interference effect. The high ellipticity can be explained by the phase difference of the harmonics. The results that we obtain facilitates the synthesis of a highly elliptical isolated attosecond pulses with duration down to 65 as, which can be served as a powerful tool to explore the ultrafast dynamics of molecules and study chiral light-matter interaction.

Section: Theoretical Methodsmentioning

confidence: 99%

Generation of elliptical isolated attosecond pulse from oriented H2+ in a linearly polarized laser field

Xing¹,

Zhang²,

Huo³

et al. 2022

Self Cite

“…Additionally, semi-integer order harmonics are observed in the harmonic spectrum. Unlike traditional explanations that rely on harmonic absorption and quantum leap theory, [38] it is proposed that these semi-integer order harmonics arise from the interference between multiple back-nucleation electron-emission harmonics.…”

Section: Introductionmentioning

confidence: 99%

Tunable spectral continuous shift of high-order harmonic generation in atoms by a plasmon-assisted shaping pulse

Wang 王,

Li 李,

Qiao 乔

et al. 2024

We have delved into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse in this investigation. Our findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping pulse. This phenomenon holds potential significance for experimental setups necessitating precisely tuned single harmonics. Notably, we have observed a modulated shift in the created harmonic photon energy, spanning an impressive range of 1.2 eV. This frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse, directly influencing the position of the peak frequency emission. Our study quantifies the dependence of this tuning range and the asymmetry of the laser pulse, offering valuable insights into the underlying mechanisms driving this phenomenon. Furthermore, our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is altered. We attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return cores. This observation introduces an innovative approach for generating semi-integer order harmonics, thus expanding our understanding of high-order harmonic generation. Ultimately, our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications, particularly those involving precise spectral control and the generation of unique harmonic patterns.

“…For example, circularly polarized high-order harmonics can be efficiently generated in a bichromatic counter-rotating circularly polarized (BCCP) laser field. [22][23][24][25][26][27][28][29][30] The BCCP field consists of a circularly polarized fundamental field and its second harmonic (SH) field with opposite rotation directions. According to the selection rule, [31,32] only (3m ± 1) order harmonics (m is a positive integer) can be obtained in an isotropic target.…”

Section: Introductionmentioning

confidence: 99%

Elliptically polarized high-order harmonic generation in nitrogen molecules with cross-linearly polarized two-color laser fields

Zhai

Qin

et al. 2023

Circularly and elliptically polarized high-order harmonics have unique advantages when used in studying the chiral and magnetic features of matters. Here, we studied the polarization properties of high-order harmonic generated from alignment nitrogen molecules driven by cross-linearly-polarized two-color laser fields. Through adjusting various laser parameters and targets, such as the relative phase, the crossing angle, the intensity ratio of driving fields, and the molecular alignment angle, we obtained highly elliptically polarized high-order harmonics with the same helicity in a wide spectral range. It provides a possible and effective way to generate elliptically polarized attosecond pulses. Finally, we show the probability of controlling the spectral range of elliptically polarized harmonics.