Polarization properties of below-threshold harmonics from aligned molecules H2+ in linearly polarized laser fields

Dong, Fulong; Tian, Yao; Yu, Shujuan; Wang, Shang; Yang, Shu-Qing; Chen, Yanjun

doi:10.1364/oe.23.018106

Cited by 16 publications

(14 citation statements)

References 42 publications

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“…In the modified SFA, only these two lowest bound states and the continuum states are included in the evolution of the system, the contributions of other bound states are omitted. Some lower excited states have been shown to contribute importantly to emission of lower-order harmonics for molecules with small R [26]. For molecules with large R, our analyses in Fig.…”

Section: Ellipticity Of the Nth Plateaumentioning

confidence: 73%

“…We expect that the NTH plateau of θ = 60 0 can be more easily influenced by the contributions of lower bound states. As the amplitudes of bound-bound transition depend on the laser wavelength [26], so do the contributions of the lower bound states to NTH. The origin of the NTH plateau will be discussed in detail later.…”

Section: Tdse Resultsmentioning

confidence: 99%

“…Due to the orientation effect [23][24][25], the molecule can emit harmonics not only parallel to the laser polarization (i.e., the parallel harmonics) but also perpendicular to the laser polarization (i.e., the perpendicular harmonics). It has been shown that for molecules with small internuclear distances R, lower-order NTH harmonics, emitted in strong linearly-polarized laser fields, can show high ellipticity [26]. This high ellipticity of lower-order harmonics arises from the resonance effect between the ground state and several lower excited states of the molecule.…”

Section: Introductionmentioning

confidence: 99%

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Ellipticity of near-threshold harmonics from stretched molecules

Dong

et al. 2015

Opt. Express

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We study the ellipticity of near-threshold harmonics (NTH) from aligned molecules with large internuclear distances numerically and analytically. The calculated harmonic spectra show a broad plateau for NTH which is several orders of magnitude higher than that for high-order harmonics. In particular, the NTH plateau shows high ellipticity at small and intermediate orientation angles. Our analyses reveal that the main contributions to the NTH plateau come from the transition of the electron from continuum states to these two lowest bound states of the system, which are strongly coupled together by the laser field. Besides continuum states, higher excited states also play a role in the NTH plateau, resulting in a large phase difference between parallel and perpendicular harmonics and accordingly high ellipticity of the NTH plateau. The NTH plateau with high intensity and large ellipticity provides a promising manner for generating strong elliptically-polarized extreme-ultraviolet (EUV) pulses.

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Section: Ellipticity Of the Nth Plateaumentioning

confidence: 73%

Section: Tdse Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ellipticity of near-threshold harmonics from stretched molecules

Dong

et al. 2015

Opt. Express

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“…The range of harmonic ellipticity is ε h ∈ [0, 1]. Equation (2) shows that high HHG ellipticity can be expected when the intensity of the perpendicular harmonic is comparable to the parallel one and there is a phase difference of δ 1 ∼ π/2 [20].…”

Section: A Numerical Methodsmentioning

confidence: 99%

“…This polarization effect of HHG has attracted great attentions in recent years, as it implies that one can acquire elliptically-polarized XUV or EUV ultrashort pulses with HHG in a linearly-polarized laser field [14]. A great deal of experimental and theoretical efforts have been devoted to the complex origins of this HHG polarization [15][16][17][18][19][20][21]. On the whole, this polarization is associated with the atomic or molecular properties in strong laser fields.…”

Section: Introductionmentioning

confidence: 99%

High ellipticity of harmonics from molecules in strong laser fields of small ellipticity

Sun,

Chen,

et al. 2021

Preprint

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We study high-order harmonic generation (HHG) from aligned molecules in strong elliptically polarized laser fields numerically and analytically. Our simulations show that the spectra and polarization of HHG depend strongly on the molecular alignment and the laser ellipticity. In particular, for small laser ellipticity, large ellipticity of harmonics with high intensity is observed for parallel alignment, with forming a striking ellipticity hump around the threshold. We show that the interplay of the molecular structure and two-dimensional electron motion plays an important role here. This phenomenon can be used to generate bright elliptically-polarized EUV pulses.

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Recent progress of below-threshold harmonic generation

Xiong

Peng

Gong

2017

J. Phys. B: At. Mol. Opt. Phys.

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The harmonics generated from the interaction of a strong laser field with atoms and molecules in the gas phase can be applied as coherent light sources and detecting techniques for structures and dynamics in matter. In the last three decades, the most prevailing experimental and theoretical studies have been focused on the high-order harmonic generation due to its applications in attosecond science. However, low-order harmonics near the ionization threshold of the target have been less explored, partially because the spectrum in this region is more complicated from both the theoretical and experimental point of view. After several pioneering investigations in the mid 1990s, near threshold harmonics (NTHs) begun to draw a great attention again because of the development of high repetition rate cavity enhanced harmonics about 10 years ago. Very recently, NTHs have attracted a lot of experimental and theoretical studies due to their potential applications as light sources and complicated mechanisms. In this topical review, we will summarize the progress of NTHs, including the early and recent experimental measurements in atoms and molecules, as well as the relevant theoretical explorations of these harmonics.

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Polarization properties of below-threshold harmonics from aligned molecules H2+ in linearly polarized laser fields

Cited by 16 publications

References 42 publications

Ellipticity of near-threshold harmonics from stretched molecules

Ellipticity of near-threshold harmonics from stretched molecules

High ellipticity of harmonics from molecules in strong laser fields of small ellipticity

Recent progress of below-threshold harmonic generation

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