Propagation of evanescent wave through surface-attached nanobubbles: A 2D simulation

We numerically study the propagation of evanescent waves at the interface between water and glass. Due to the existence of surface-attached nanobubbles, the intensity of the evanescent wave passed into water increases by 30 times, which can be used in the dark-field inspection. The relationship between the intensity of the evanescent wave and contact angle is found and analyzed. It provides a possible method to measure the contact angle. Additionally, the theoretical distribution of bright and dark areas on nanobubbles is consistent with experimental data, where the middle of the nanobubble is darker than the edge. The right edge of the bubble is brighter than the left edge, which corresponds to the incident direction of the light source.