Figure 7: Experimental comparison between conventional phase matching with a 2.2-µm driver and unconventional phase matching with a 0.8-µm driver

Experimental HHG spectra with a 0.8 µm and a 2.2 µm driver in helium and neon. The different generation parameters are summarized in Table 1. All spectra are recorded with the same grating (2400 g/mm), except the 2×10^(15) W/cm^2 case, recorded with a 1200 g/mm grating. For the latter, the diffraction efficiency above 260 eV was determined experimentally by recording the same spectrum with both gratings and using the 2400 g/mm diffraction efficiency as a reference.

针对氦气与氖气介质，采用0.8 µm和2.2 µm的驱动激光脉冲开展高次谐波产生（High Harmonic Generation, HHG）光谱实验。实验涉及的各类高次谐波产生参数汇总于表1。所有光谱均采用规格为2400线/毫米的光栅进行记录，仅功率密度为2×10¹⁵ W/cm²的工况除外——该工况采用1200线/毫米的光栅采集。针对该工况，研究人员通过使用两种光栅分别记录同一份光谱，并以2400线/毫米光栅的衍射效率作为参照，实验测定了260 eV以上波段的衍射效率。