Photostriction in BiFeO3: wavelength dependence
  In electrically polar solids optomechanical effects result from the combination of two main processes, electric field-induced strain and photon-induced voltages. Whereas the former depends on the electrostrictive ability of the sample to convert electric energy into mechanical energy, the latter is caused by the capacity of photons with appropriate energy to generate charges and, therefore, can depend on wavelength.We report here on mechanical deformation of BiFeO3 and its response time to discrete wavelengths of incident light ranging from 365 to 940 nm. The mechanical response of BiFeO3 is found to have two maxima in near-UV and green spectral wavelength regions. 
B. Kundys, M. Viret, C. Meny, V. Da Costa, D. Colson, and B. Doudin
cond-mat.mtrl-sci cond-mat.str-el