Deep‐learning powered whispering gallery mode sensor based on multiplexed imaging at fixed frequency

During the last decades the whispering gallery mode based sensors have become a prominent solution for label-free sensing of various physical and chemical parameters.At the same time,the widespread utilization of the approach is hindered by the restricted applicability of the known configurations for ambient variations quantification outside the laboratory conditions and their low affordability,where necessity on the spectrally-resolved data collection is among the main limiting factors.In this paper we demonstrate the first realization of an affordable whispering gallery mode sensor powered by deep learning and multi-resonator imaging at a fixed frequency.It has been shown that the approach enables refractive index unit(RIU)prediction with an absolute error at 3×10^(-6) level for dynamic range of the RIU variations from 0 to 2×10^(-3) with temporal resolution of several milliseconds and instrument-driven detection limit of 3×10−5.High sensing accuracy together with instrumental affordability and production simplicity places the reported detector among the most cost-effective realizations of the whispering gallery mode approach.The proposed solution is expected to have a great impact on the shift of the whole sensing paradigm away from the model-based and to the flexible self-learning solutions.

Detection of per-and polyfluoroalkyl water contaminants with a multiplexed 4D microcavities sensor

The per-and polyfluoroalkyl substances(PFAS)are a group of organofluorine chemicals treated as the emerging pollutants that are currently of particularly acute concern.These compounds have been employed intensively as surfactants over multiple decades and are already to be found in surface and ground waters at amounts sufficient to have an effect on human health and ecosystems.Because of the carbon–fluorine bonds,the PFAS have an extreme environmental persistence and their negative impact accumulates with further production and penetration into the environment.In Germany alone,more than thousands of sites have been identified as contaminated with PFAS;thus,timely detection of PFAS residue is becoming a high priority.In this paper,we report on the high performance optical detection method based on whispering gallery mode(WGM)microcavities applied for the first time to detect PFAS contaminants in aqueous solutions.A self-sensing boosted 4D microcavity fabricated with two-photon polymerization is employed as an individual sensing unit.In an example of the multiplexed imaging sensor with multiple hundreds of simultaneously interrogated microcavities we demonstrate the possibility to detect the PFAS chemicals representatives at a level down to 1 ppb(parts per billion).