Nonreciprocal reflection of a subwavelength hole array

We present measurements of the wavelength-dependent reflectivity of a subwavelength metal hole array on a glass substrate. We compare the observed resonant structures with those found in transmission and note a nonreciprocity under illumination from the air versus the glass side. This can be used to verify on which interface the surface plasmons are resonantly excited and to estimate the losses in the subwavelength channels. (C) 2003 Optical Society of America.