  Above-bandgap optical illumination induces a transformation from tilted
tetragonal-like (T-like) and rhombohedral-like (R-like) phases to an untilted
T-like phase in compressively strained BiFeO3. Optical excitation leads to an
out-of-plane lattice expansion in the T-like phase. The transformation proceeds
in regions with boundaries between the T-like and tilted R-like and tilted
T-like phases, consistent with the motion of a boundary. The optically induced
transformation indicates that there are new optically driven routes towards
nanosecond-scale control of phase transformations in ferroelectrics and
multiferroics.
