(a) PolScope texture of bend Frederiks transition in the N phase, showing the local optic axis projected onto the cell’s plane (black bars) and the local optical retardation of the cell (pseudocolors). Scale bar, 10 μm. Inset shows bend-twist of the director (red symbols; nails depict titled director). (b) PolScope texture of bend Frederiks transition in the Ntb phase showing only splay and saddle-splay deformations of the optic axis. The inset shows the initial nucleating site in the shape of an axially symmetric toroidal focal conic domain29 with green lines following the optic axis. Scale bar, 10 μm. (c) Optical retardation of the realigned Ntb structure measured along the lines A and B shown in b. (d) Threshold voltage of expansion of a realigned Ntb versus cell thickness d, for T=87 °C (filled symbols) and T=86 °C (open symbols).