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

Abstract

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.

Integrated Microresonator-Based Microwave Photonic Sensors Assisted by Machine Learning

“…Recent developments in photonic integration have unveiled exciting possibilities for pushing the performance boundaries of integration platforms to unprecedented levels. The emergence of integration platforms [56][57][58][59][60][61] and the evolution of functional thin-film materials [62][63][64] facilitate the customisation of MWP sensors for various applications. The SOI photonic devices offer the advantages of immune electromagnetic interference capabilities.…”

Integrated Microwave Photonic Sensors Based on Microresonators

“…[13][14][15][16][17][18][19] Amid the array of existing approaches, the integrated MWP sensors, which utilize integrated photonic devices, such as microrings, microdisks, and photonic crystals, as the sensor probe, emerge as particularly appealing due to their inherent high sensitivity to environmental conditions, small size, and mass-production availability. [11] Moreover, the development of various integration platforms [22][23][24][25][26][27] as well as the evolution of functional thin-film materials [28][29][30] and advanced data processing techniques such as machine learning (ML) algorithms and deep neural networks (DNNs), [31,32] serves to propel the performance boundaries of integrated MWP sensors continuously.…”

Real-Time In Vivo Sensing of Nitric Oxide Using Photonic Microring Resonators

“…As depicted in Figure 5e, when the MRR comes in contact with the PBS-soaked wound surface tissue at t = ∼1 min, the guided mode shows a decrease in the refractive index due to the cladding refractive index changing from air to liquid, which includes the reduction of the refractive index of the Nafion layer after interacting with effluent/PBS and swelling. 42,43 This causes the initial blue shift of the resonance peak. Note that the negative thermo-optic coefficient of Nafion makes the device relatively temperature insensitive to cause temperature induced shift (Figure S2).…”