Enhancement of High-Order Harmonic Generation in Low-Density Ti Plasma Plumes Induced by Intense Laser Fields

High harmonic generation (HHG) of laser-ablated plasma plumes driven by an intense laser field is an effective method for generating coherent extreme ultraviolet radiation. We investigated the enhancement of high-order harmonics by the interaction of intense laser fields and laser-ablated low-density Ti plasma plumes. By analyzing the mechanism of HHG, the microscopic effect was proved to account for the enhancements of H27-H31. In addition, the density distribution of Ti plasma plumes was estimated and verified that the intensities of different order harmonics were influenced by different regions of Ti plasma plume density. Our results provide a pathway for optimizing the phase-matching conditions of resonant harmonics to improve the harmonic yield by means of controlling the density of laser-ablated plasma plumes (LPPs).