Tunable Plasmonic Neutral Density Filters and Chromatic Polarizers: Highly Packed 2D Arrays of Plasmonic Nanoparticle on Elastomer Substrate

Abstract

Highly packed gold nanocube (AuNC) 2D arrays sandwiched between two layers of polydimethylsiloxane (PDMS) substrates act as an optical neutral density filter (NDFs) and a chromatic polarizer. Upon mechanical stretching, the intensity of the absorption spectrum of the AuNC 2D arrays-PDMS is found to decrease evenly in the UV, visible, and NIR regions of the electromagnetic spectrum. The color of the polarized light transmitted through the filter is dependent on its angle of polarization. The localized surface plasmon resonance (LSPR) extinction spectrum of the AuNC arrays arises mainly from scattering rather than absorption, unlike standard NDFs where their function is based on light absorption. Absorption of light causes heat generation that has a negative impact on the function of the NDFs. The ordering of the AuNCs inside the array after stretching was examined by dark field imaging, polarization-dependent optical measurements, and surface-enhanced Raman scattering spectroscopy