Chalcogenide rib waveguides for the characterization of spray deposits

With the aim to develop optical micro-sensors for "on-line" measurement of spray deposits on plant leaves, and thus to optimize the use of phytosanitary inputs in agriculture, straight waveguides based on GeSeTe chalcogenide layers were elaborated and their sensitivity to water droplet deposition was tested. As expected, water, the main constituent of pesticides, absorbed part of the evanescent wave of the guided light, which led to a decrease in the intensity transmitted at the output of the waveguides. Both experimental and simulation results proved that the position of the drop on the waveguide had no impact on the intensity measured at the guide outlet. At the opposite, they highlighted the correlation between the light intensity at the outlet and the volume and number of deposited droplets: the greater the volume of the drop and the greater the number of drops, the greater the decrease in intensity.