Light-Driven Pitch Tuning of Self-Assembled Hierarchical Gratings

Gratings are of vital importance in modern optics. Self-assembled cholesteric liquid crystal (CLC) gratings have attracted intensive attention due to their easy fabrication and broad applications. However, simultaneously achieving arbitrary patterning and delicate tuning of CLC gratings remains elusive. Here, light-driven pitch tuning is accomplished in hierarchical gratings formed in a molecular switch doped CLC. We fabricate a checkerboard hierarchical CLC grating for a demonstration, whose pitch is optically tuned from 4.6 mu m to 10.7 mu m. Correspondingly, the first-order diffraction angle continuously changes from 9.4 degrees to 4.8 degrees and a significant polarization selectivity is also observed. In addition, hierarchical CLC gratings with triangular wave pattern, Archimedean spiral, and radial stripes are also demonstrated. This work creates new opportunities for soft-matter-based intelligent functional materials and advanced photonic devices.