2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/85764We present a symmetry-based theory of the depolarization induced by subwavelength metal hole arrays. We derive the Mueller matrices of hole arrays with various symmetries (in particular square and hexagonal) when illuminated by a finite-diameter (e.g. gaussian) beam. The depolarization is due to a combination of two factors: (i) propagation of surface plasmons along the surface of the array, (ii) a spread of wave vectors in the incident beam.4 pages, 1 figureOpticstext