Waveform control in selective enhancement of single-order harmonic

Abstract

We theoretically propose an effective scheme to selectively enhance a single-order harmonic in the spectral continuum via the laser waveform control of a two-color chirped pulse. Through controlling the pulse durations and chirps of the two-color field, the wavelength tunable single-order harmonics from 87th order to 176th order can be selectively enhanced by 15 times-20 times in comparison with their neighbors. Theoretical analyses show that the selective enhancement of the single-order harmonic is because of the folded structure on the harmonic emission process, which is caused by the multiple accelerations of the free electron in the specific folded laser waveform.