Phase-Controlled Two-Color High-Order Harmonic Generation in Laser-Produced Plasmas

Next-generation nanolithography devices make use of extreme ultraviolet (EUV) radiation, emitted by a laser-produced plasma (LPP) in tin, to print nanometer-sized features on semiconductor wafers. The EUV emission characteristics of such LPPs depend strongly on the plasma properties, which are conditioned by the laser pulse that generates the plasma. Therefore, it is useful to understand how different laser parameters affect the spatial and temporal properties of the formed plasma. High-order harmonic generation (HHG) in the LPP by an auxiliary femtosecond laser may serve as a novel method to gain time-resolved information from the LPP expanding in the vacuum. In our former work, we have successfully demonstrated HHG up to harmonic order 25 in Sn LPP [1]. Scanning laser parameters and delay between pump and fundamental laser pulses allows us to optimize the harmonic yield and observe the temporal dynamics of the laser-produced tin plasma expansion into the vacuum.