Strong light concentration at the subwavelength scale by a metallic hole-array structure.

A metallic two-dimensional hole-array (2DHA) sample is successfully fabricated and its transmission property measured at mid-infrared wavelengths (lambda ~ 1.5-20 microm). At the plasmonic resonance, the 2DHA sample exhibits a normal incidence transmittance of 80% at lambda = 7.6 microm. This corresponds to more than twice as much light that is transmitted as it impinges directly on the holes at the maxima of transmittance. This exceedingly large enhancement is attributed to a strong plasmonic resonance and an effective light concentration through an ultrathin metal film of 50 nm. This advancement will pave the way to a much enhanced infrared detection using a simple and compact 2DHA architecture.