Mechanically-controlled multifaceted dynamic transformations in twisted organic crystal waveguides

This study introduces mechanically induced novel phenomena such as standing, leaning, stacking, and interlocking behaviors in naturally twisted optical waveguiding microcrystals on a substrate. The twisted crystal self-assembled from 2,4-dibromo-6-(((2-bromo-5-fluorophenyl)imino)methyl)phenol is flexible and emits orange fluorescence. Crystal’s mechanical flexibility in the perpendicular direction to (001) and (010) planes can be attributed to intermolecular interactions, including C-H···Br, N-H···O, C-H···O, and π···π stacking interactions. Through a systematic process involving step-by-step bending and subsequent optical waveguiding experiments at each bent position, a linear relationship between optical loss and mechanical strain is established. Additionally, the vertical standing and leaning of these crystals at different angles on a flat surface and the vertical stacking of multiple crystals reveal the three-dimensional aspects of organic crystal waveguides, introducing light trajectories in a 3D space. Furthermore, the integration of two axially interlocked twisted crystals enables the coupling of polarization along their long axis. These novel crystal dynamics expand the horizons of crystal behavior and have the potential to revolutionize various applications, rendering these crystals invaluable in the realm of crystal-related science and technology.