Time-dependent optimization of laser-produced molecular plasmas through high-order harmonic generation

摘要： Analysis and characterization of laser-produced plasmas (LPPs) require the advanced methods for determination of different multiparticle component formation and spreading. Time-resolved high-order harmonic generation (HHG) in spreading LPPs allows determining optimal conditions for this process. One of the most important parameters of HHG in LPP is the delay between the heating and driving pulses. We demonstrate that the optimization of delays allows achieving the maximal harmonic yields in LPP created on the surfaces of the solid targets possessing different molar masses (m). The optimal delays (t) for B4C, ZnO, GaP, GaAs, and Ag2S plasmas were determined to be approximately 200, 300, 350, 500, and 700 ns, respectively. These variations of delays correspond to the t1(m)0.5 dependence for different materials. We demonstrate the applicability of the proposed method for analysis of the resonance-enhanced harmonics in atomic and molecular plasmas (Mo and MoS2) and for studies of large perovskite aggregates as potential emitters of harmonics. This diagnostic technique can also be applied to the analysis of the presence of different nanostructures in LPPs through HHG with a high spatiotemporal resolution.