Three-dimensional reconstruction of topological deformation in chiral nematic microspheres using fluorescence confocal polarizing microscopy

Chiral nematic droplets exhibit abundant topological defect structures, which have been intensively studied, both theoretically and experimentally. However, to observe and reconstruct the exact shape of three-dimensional (3D) defect structures has been a challenging task. In this study, we successfully reconstruct the 3D defect structures within a CLC microsphere with long helical pitches by combining polarized optical microscopy (POM) and laser scanning type fluorescence confocal polarizing microscopy (FCPM). The obtained confocal stack images provide us with the vertical location of disclination defects, to allow reconstruction of the full 3D structures. The reconstructed 3D structures can be viewed from different directions, providing a better understanding of the topological structure. Moreover, the defect lines are identified to be + 1 defects, different from the previous prediction. Thus, FCPM provides an excellent tool to study the complex topological configuration in microspheres, and fosters its potential applicability in new devices based on topologically structured soft media.