Resonant Excitation of Surface Plasmon for Wakefield Acceleration by Beating GW Lasers on Smooth Cylindrical Surface.

We present a theoretical and numerical study of resonant surface-plasmon (SP) excitation driven by the beating of two copropagating laser pulses on a smooth cylindrical plasma-vacuum interface. Analytical formulas for the SP dispersion relation, field amplitude, geometric coupling factor, and resonance conditions are derived and validated by fully three-dimensional particle-in-cell simulations. We show that the curvature-modified SP dispersion enables the optical beat wave to resonantly drive an axial SP wakefield that leaks into the vacuum channel. This enables a grating-free surface-plasmon phase-matching mechanism, which is not available on a smooth planar interface. Under matched resonance conditions, few-gigawatt (GW) lasers can drive tens of GV/m SP wakefields and initiate electron trapping, while tens to hundreds of GW drivers can reach sub-TV/m fields. It therefore opens a low-power, grating-free route toward portable laser-driven surface plasma wakefield accelerators.