Theoretical research on the effective generation of an isolated attosecond pulse from the synthesized pulse laser with optimized waveform

Abstract A mid-infrared femtosecond pulse laser with a single cycle and high intensity is an ideal driving light source for generating isolated attosecond pulses. Due to current experimental limitations, it is difficult to directly achieve this type of laser light source in the laboratory. In this paper, we obtain such an ideal light source by adding a Ti sapphire pulse to the combined pulse laser consisting of two mid-infrared pulses. Specifically, by combining the synthesized pulse consisting of 8 fs/1200 nm/1.62 × 10 14 W cm −2 and 12 fs/1800 nm/2.71 × 10 14 W cm −2 with an additional 8 fs/800 nm/1.26 × 10 14 W cm −2 Ti sapphire pulse, the resulting electric field waveform is very close to that of a 1170 nm femtosecond pulse with an intensity of 1.4 × 10 15 W cm −2 , a single-cycle pulse width, and a carrier-envelope phase of 0.25 π . Numerical simulations show that both cases produce high-order harmonic emission spectra with broadband supercontinuum spectra, however, the bandwidth of the supercontinuum spectra and the harmonic intensities in the synthesized pulses are significantly better than those in the single 1170 nm pulse. After inverse Fourier transform, we obtain 66 as a high-intensity isolated attosecond pulse, whose intensity is five orders of magnitude higher than that of a monochromatic field. Here, the phase differences between three combined pulse lasers have little effect on the numerical simulation results when they vary in the range of 0.3 π .