A theoretical study of broadband extraordinary optical transmission in gold plasmonic square nanohole arrays and its application on refractive index sensor

Extraordinary optical transmission (EOT) behaviour is investigated in a subwavelength plasmonic nanostructure, consisting of a gold film perforated with a square nanohole array and deposited on a silicon dioxide substrate. The essential aspect of the proposed structure is the periodic disorder that enables broadband transmission peaks in the visible and near-infrared region and reduces the structure's size, which mainly arises from the excitation of localized surface plasmon resonances. Optical cavity modes formed in the nanoholes and the hybridization of plasmon modes. Further, the performance of the proposed nanostructure as a plasmonic sensor is analyzed by increasing the index of refraction of the local environment; the EOT exhibit remarkable refractive index sensitivity of up to 944 nm/RIU, a figure of merit of 15.25, and a contrast ratio of 47% are realized. The proposed structure has some practical significance for designing low-cost and effective sensing devices.

Automated summary

The extraordinary optical transmission (EOT) behavior of a subwavelength plasmonic nanostructure is investigated. The structure, composed of a gold film with a square nanohole array on a silicon dioxide substrate, exhibits broadband transmission peaks and reduced size due to the excitation of localized surface plasmon resonances. The nanostructure also demonstrates high sensitivity and contrast as a plasmonic sensor.