Field enhancement of intense laser pulses in a subwavelength plasma aperture

The interaction of intense, ultra-short laser pulses with nanostructures offers promising avenues for spatiotemporal light control. While enhanced optical transmission through subwavelength apertures has been extensively studied in the linear regime, its extension to ultra-short, high-intensity pulses remains largely unexplored. Here, we demonstrate, through three-dimensional particle-in-cell simulations, significant field enhancement of intense laser pulses in subwavelength plasma apertures. The enhancement exhibits a non-resonant character, remaining robust across a wide range of plasma densities and saturating above approximately 20nc, while showing minimal dependence on wall thickness. Analysis of the Poynting vector reveals that energy concentration arises from interference between the incident field and back-scattered longitudinal field components. This size-dependent transmission in plasma apertures generalizes to planar geometries and enables potential applications such as plasma-based dichroic filters operating at extreme intensities.