  Interaction between metal surface waves and periodic geometry of
subwavelength structures is at the core of the recent but crucial renewal of
interest in plasmonics. One of the most intriguing points is the observation of
abnormal strong transmission through these periodic structures, which can
exceed by orders of magnitude the classical transmission given by the filling
factor of the plate. The actual paradigm is that this abnormal transmission
arises from the periodicity, and then that such high transmission should
disappear in random geometries. Here, we show that extra energy can be coupled
through the subwavelength structure by adding a controlled quantity of noise to
the position of the apertures. This result can be modelled in the statistical
framework of stochastic resonance. The evolution of the coupled energy with
respect to noise gives access to the extra energy coupled at the surface of the
subwavelength array.
