The stencil mask method is used to fabricate large-scale metal films perforated with periodic hole arrays,and the enhanced transmission through metal films perforated with periodic hole arrays is explored experimentally in the middle infrared wavelength.By studying the transmission spectra of metal films perforated with periodic hole arrays surrounded by different mediums,we find that transmission spectra show redshifts with the increasing of medium′s refractive index.By comparing the sensitivit...