SAW phase modulation by optical illumination of graphene composite films deposited on LiNbO3

Propagation of surface acoustic waves in YZ LiNbO₃ overlaid with graphene flakes has been investigated and its optical response to illumination by 633 nm light from He-Ne laser was studied. The heating of the sample surface due to optical absorption by the graphene led to a downshift in the transmitted SAW phase caused by the wave velocity dependence on temperature. The proposed simple model based on optothermal SAW phase modulation was found to be in good agreement with the experimental results.