Abstract
We investigate high-order harmonic generation in H2+ by using two sequential laser pulses, which consist of a 800-nm pump pulse and a time-delayed 1600-nm probe pulse. Based on the solution of the time-dependent Schrödinger equation, we demonstrate that the harmonic cutoff in our two-pulse scheme is significantly extended compared to that in the 1600-nm probe pulse alone. Meanwhile, the harmonic efficiency is enhanced by 2-3 orders of magnitude due to charge-resonance-enhanced ionization steered by the 800-nm pump pulse. By using a probe pulse with longer wavelength, our scheme can be used for efficient high harmonic generation in the water window region. In addition, the influence of the intensity of the pump pulse and the relative time delay of the two laser pulses on the harmonic generation are also investigated.
Highlights
High-order harmonic generation (HHG) through the laser-matter interaction has been a topic of great interest over the last two decades [1] for its potential applications as a tabletop source of XUV and soft x-ray emission
By solving the time-dependent Schrödinger equation (TDSE), we find that in our scheme the harmonic cutoff is extended and the harmonic yield is enhanced by about 2-3 orders of magnitude compared to that in the probe pulse alone
Region and move to larger internuclear distances, where the ionization rate is higher than that at the equilibrium internuclear distance due to the smaller ionization potential [see Procedure 2 in the Fig. 2]. This can be confirmed by the internuclear distance of the moving H+2 in Fig. 1(c), which has reached a peak of 3.6 a.u. at 4T0 (T0 is the optical cycle of the 1600-nm probe pulse)
Summary
High-order harmonic generation (HHG) through the laser-matter interaction has been a topic of great interest over the last two decades [1] for its potential applications as a tabletop source of XUV and soft x-ray emission. HHG has become an important approach to generate attosecond pulses [4,5,6,7,8,9] and provides a novel tool to realtime probe electron dynamics in atoms and molecules [10,11,12,13] and to tomographically image molecular orbital [14,15,16,17,18,19] These potential applications of HHG is still limited by two factors: bandwidth and yield of the harmonic spectrum. By using a probe laser pulse with longer wavelength, our scheme can be used for efficient harmonic emission in the water window region
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