The effect of tarnish on extraordinary optical transmission of silver subwavelength slit gratings

Tarnishing of silver nanostructures strongly affects their optical performance. We report that in the course of months under regular laboratory conditions, subwavelength silver gratings undergo tarnishing differently from plain silver films: instead of thin layer of evenly distributed silver sulfide, a random pattern of rare larger crystals is formed across the grating area. The observable changes in the optical transmittance are specific: the Wood diffraction anomaly degrades totally while the extraordinary transmission peak noticeably attenuates. The high sensitivity of silver gratings to sulfur is prospective for sensor applications.