Intensity-dependent electron correlations in nonsequential double ionization driven by spatially inhomogeneous laser fields

Using a three-dimensional classical ensemble model, we theoretically investigate the intensity dependence of nonsequential double ionization (NSDI) of argon atoms driven by a spatially inhomogeneous laser field. The numerical results show that the correlated electron momentum distribution (CEMD) is highly sensitive to the laser intensity, with the most pronounced changes appearing in the low- and high-momentum regions. In the high-momentum region, the relative contribution of electron pairs to NSDI first increases and then tends to stabilize with increasing laser intensity, while the distribution remains concentrated near the diagonal. In contrast, in the low-momentum region, the initially focused diagonal distribution gradually broadens and evolves into a pronounced arc-like structure at high intensity. Back analysis reveals that the dominant recollisionimpact ionization (RII) events can be classified into four typical trajectory classes. Electron pairs originating from different trajectory classes populate different regions of the CEMD and exhibit distinct momentum-correlation patterns. The intensity-dependent relative weights of these trajectory classes are responsible for the observed evolution of the CEMDs. These results provide a clear physical picture for controlling correlated electron dynamics in spatially inhomogeneous laser fields.