Array of sub-wavelength holes etched on to a thin metal film is a class of plasmonic structure, more commonly known as a metal nanohole array (NHA). This class of structure exhibits surface plasmon (SP) resonance. The SP resonance in metal NHAs are composite of the two main kind of plasmonic resonance - the surface plasmon polariton (SPP) resonance and localized surface plasmon resonance (LSPR) along with evanescent propagating waveguide modes. This variety and richness in the physics of their resonant characteristics, make metal NHAs attractive and useful in various field of application, from refractive index sensing to light emission and photovoltaics. When special configurations are made using metal NHAs, they also exhibit some special resonance, like Tamm plasmon (TP) resonance, Fano resonance, absorption induced transparency (AIT) and surafce lattice resonance (SLR).

In this review, the physics and application of metal NHAs is presented. In presenting the physics of metal NHAs, the physics of single sub-wavelength holes and sub-wavelength hole arrays (NHAs) on metal films are described, by analysing their transmission and dispersion relation characteristics. Thereafter, some of the devices reported so far, whose operation are based on the optical characteristics of metal NHAs are presented. Application of mtak NHAs in the fields of biosensing, light emission - lasers, photo-voltaics, optical communication etc are presented and analysed. Finally, based on the current trend of research in this field, the future of metal NHAs is presented. Every project has a beautiful feature showcase page. It's easy to include images in a flexible 3-column grid format. Make your photos 1/3, 2/3, or full width.