Ordered photonic nanojet arrays for luminescent optical sensing in liquid and gaseous media

Abstract

Here we demonstrate a novel sensor structure based on ordered arrays of dielectric microstructures produced via CMOS-compatible technology. The microstructures are fabricated on a transparent substrate and covered with a chemosensitive dye-doped polymer layer. Under excitation from the substrate side, the microstructures generate extended and intensive photonic nanojets into the polymer layer, selectively exciting it, thus forming a large distributing sensing area. The fabricated arrays were used for sensor response enhancement of luminescent dye-based chemosensitive receptors for metal ions detection in aqueous media and volatile organic compounds in gaseous media. We have shown that the sensor's detection limit depends on both PNJ length and intensity, which can be controlled by the refractive index difference between the microstructure and the sensitive layer, the parental microparticle shape and size, and spatial ordering and period of the microstructures in the array. It was found that once all the parameters are optimized, the photonic nanojet of 10λ length and peak intensity higher than 10 is generated. That results in a 50-fold reduction of the limit of detection for analytes in aqueous media and a 15-fold reduction of the limit of detection for analytes in gaseous media. The obtained results demonstrate a high potential for fabricated structures in the next-generation lab-on-chip device development.