Rotation of liquid crystal microdroplets in the intensity minima of an optical vortex beam

An optical vortex is characterized by its donut-shaped intensity distribution and helical phase structure. In this study, we demonstrate that an optical vortex beam, generated by a spatial light modulator, can trap, circulate, and rotate liquid crystal microdroplets of various sizes at different positions within the beam. Our findings indicate that larger microdroplets are trapped at intensity minima without altering their internal liquid crystal orientation, which is fluid by nature, and the rotation of microdroplets were observed. This rotation, a rare phenomenon, occurs without damaging or altering the inner liquid crystal molecules, offering an advantage over traditional circularly polarized optical trapping, which can generally alter inner molecular arrangements of liquid crystal. This report details the relationship between trapped particle size, trapping position, and rotation angle of liquid crystal microdroplets within an optical vortex beam.