Regular Article – Ultraintense and Ultrashort Laser Fields
Isolated attosecond pulse generation in the water window by tailored MIR femtosecond pulse laser
School of Physics, Changchun University of Science and Technology, 130022, Changchun, People’s Republic of China
Accepted: 5 August 2022
Published online: 13 September 2022
We numerically simulate the high-order harmonic generation in the frequency domain and attosecond pulse generation in the time domain from helium atom irradiated by a tailored MIR femtosecond pulse laser, which is synthesized by a 12 fs/1800 nm/2.71 × 1014 Wcm−2 driving pulse laser and two gating pulse lasers including an 8 fs/1200 nm/1.62 × 1014 Wcm−2 and an 8 fs/800 nm/1.26 × 1014 Wcm−2. This combined pulse has the characteristics of a single-cycle mid-infrared femtosecond pulse with high intensity and stable carrier envelope phase, which current few-cycle MIR femtosecond pulse laser technology can’t qualify. It is found that broadband supercontinuum harmonic spectra with regular plateau structure are generated, and the radiation efficiency of the harmonics is greatly improved compared with the case of a single pulse and two-color optimal synthesize pulses. After inverse Fourier transform, an isolated 66 as pulse with higher intensity can be obtained by superposing supercontinuum harmonics from the 70th to the 515th order. Here, the phase differences between three pulses have little effect on the numerical simulation results when they vary in the range of 0.3π.
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