Processing, Characterization, and Impact of Nafion Thin Film on Photonic Nanowaveguides for Humidity Sensing

Herein, the impact and spin‐coating process of Nafion thin films on photonic nanowaveguide structures fabricated via a complementary metal–oxide–semiconductor compatible process for the first time is investigated. Particularly, the effect of Nafion thin films (≈23–776 nm) on microring resonators (MRRs) with compact waveguide sizes (480 nm by 220 nm and 380 nm by 220 nm) is focused on, where the microring provides enhanced interactions between the Nafion and light, which is related to Nafion thin‐film properties such as the refractive index, water uptake, and swelling. The results demonstrate small, compact, and cost‐effective MRR devices to characterize Nafion thin film and high‐resolution on‐chip humidity sensing for real‐time and continuous measurements.