Bulk sensing performance comparison between silicon dioxide and resonant high aspect ratio nanopillars arrays fabricated by means of interference lithography

Abstract

In this work we present the refractive index sensing performance comparison between resonant (R-NPs) and silicon dioxide (SiO2-NPs) high-aspect ratio nano-pillars arrays. Both arrays have been fabricated by laser interference lithography and reactive ion etching. The R-NPs are made by a multilayer of silicon oxide and silicon nitride distributed to act as a vertical resonant cavity with two Bragg reflectors. Several chips containing eight periodic arrays of R-NPs and SiO2-NPs were implemented following the presented fabrication process, having a height in the order of 2.5 μm, a diameter in the order of 200 nm, different pitches and aspect ratio up to 9.8. Finally, the optical responses of these arrays were measured by infiltration of fluids with different refractive indexes. The main conclusion is that sensitivity obtained for the R-NPs is more than two times higher in comparison with the SiO2-NPs sensitivity (3724 cm−1/RIU and 1652 cm−1/RIU, respectively).