Generation of a Conjoint Surface Plasmon by an Infrared Nano‐antenna Array

Localized surface plasmons (LSP) excited by optical fields have many potential applications resulting from their ability in detecting ultra‐small, ambient refractive index change. Current methods using surface nano‐patterning by means of lithography have given rise to LSP of limited propagation and interaction lengths, meaning that practical applications remain challenging. This paper describes a new all‐optical method of generating LSP by means of a carefully fabricated low dimensional nano‐structured material by using a direct‐write photochemical lithography. It is shown that the resulting array of localized surface plasmons combine or “Conjoin” to have an unprecedented large interaction length, via coupled evanescent fields, giving rise to superior spectral sensitivities; several orders of magnitude better than those quoted elsewhere and reaching 6×103 nm/RIU in the aqueous regime and 104 nm/RIU in the gaseous regime. Numerical modeling was performed that showed this design of plasmonic platform is capable of producing sensitivities of 105‐106 nm/RIU. We believe the results achieved in this investigation show that a unique conjoint surface plasmon operational mode will significantly impact areas of interest, such as single molecular dynamics, drug delivery systems etc.