Exceptional points in rolled-up tubular microcavities

We observe the crossing and anti-crossing behaviors of nearly degenerate mode pairs in a rolled-up tubular microcavity, which can be explained by weak and strong couplings between the modes. Exceptional points (EPs) are thus obtained in the tubular microcavity since they are the critical point where a transition from strong to weak coupling occurs. Rolled-up tubular microcavities with a given resonant mode approaching an EP in parameter space expanded by two continuous variables are also realized without using near-field probes. Microcavities with EPs prepared in a rolled-up way could be mechanically stable and would be used for optofluidic detection.