Polar Micro Structures of the B 2- And B 4-Phases of Bent-Shaped Lc-Molecules Resolved by Nonlinear Optical Microscopy

A nonlinear optical (NLO) microscope has been developed based on recording the second harmonic generation (SHG) signals of the B 2- and B 4-phases of bent shaped liquid crystalline (LC) materials. We observed that the microstructures of the polar order can be accurately characterized by 2D scanned images implementing this device. Specifically, we have investigated two bent-core compounds, which have either B 4 or B 2 phases at room temperature and exhibit SHG activity. The NLO microscope was calibrated according to the Maker-fringes method allowing the in situ evaluation of the relative SHG efficiency. The developed NLO microscopy device may serve as an important tool to characterize liquid crystalline features at a microscopic scale for both fundamental and applied research.