Generation of high quality sub-two-cycle pulses by self-cleaning of spatiotemporal solitons in air-plasma channels

The temporal sidelobes of few-cycle pulses seriously restrict their applications in ultrafast science. We propose a unique mechanism that enables the generation of sub-two-cycle pulses with high temporal quality based on soliton self-cleaning in air-plasma channels. A robust spatiotemporal soliton could be formed from pulse self-compression by modulating the dispersion of the air-plasma channel via the adjusted plasma density. Due to ionization, the blue-shifted soliton with a larger group velocity captures the leading sidelobes whereas the plasma generated by the soliton defocuses the trailing sidelobes, which are eventually eliminated after a long-distance propagation. The self-cleaning of spatiotemporal soliton leads to no sidelobes in the temporal profile of the sub-two-cycle pulse. The required density of the preformed plasma for arbitrary central wavelength from near-infrared to mid-infrared regime is predicted theoretically and confirmed by (3D+1) simulations.