Ferroelectric topologies in BaTiO₃ nanomembranes for light field manipulation

Ferroelectric topological textures in oxides exhibit exotic dipole-moment configurations that would be ideal for nonlinear spatial light field manipulation. However, conventional ferroelectric polar topologies are spatially confined to the nanoscale, resulting in a substantial size mismatch with laser modes. Here we report a dome-shaped ferroelectric topology with micrometre-scale lateral dimensions using nanometre-thick freestanding BaTiO₃ membranes and demonstrate its feasibility for spatial light field manipulation. The dome-shaped topology results from a radial flexoelectric field created through anisotropic lattice distortion, which, in turn, generates centre-convergent microdomains. The interaction between the continuous curling of dipoles and light promotes the conversion of circularly polarized waves into vortex light fields through nonlinear spin-to-orbit angular momentum conversion. Further dynamic manipulation of vortex light fields can also be achieved by thermal and electrical switching of the polar topology. Our work highlights the potential for other ferroelectric polar topologies in light field manipulation.