Generation of high-order single harmonics by using chirp waveform control

We present a method to generate the high-order single harmonics on the harmonic spectra. It is shown that by properly choosing the chirp parameters, the laser intensities and the pulse durations of two-color chirped pulse, the high-order single and even double harmonics can be enhanced and generated on the harmonic spectra. The reason behind the single and double harmonic generation is because the nonlinear electron acceleration in the chirp region caused by the reversed sub-peak structure. The results are beneficial to the generation of single and double harmonic light sources.