  We deposited epitaxial thin films of Morphotropic Phase Boundary (MPB)
  Pb0.65Ba0.35Nb2O6 (PBN:65) on MgO substrates using pulsed laser deposition.
Afterwards, a novel transmission optical experiment was developed to measure
the electric field-induced bending angle of the thin film sample using a
divergent incident light. From which the electric field-induced strain was
obtained, and it was used to calculate the electrostrictive constant of the PBN
thin film. The result is 0.000875 um2/V2, and it is consistent with what we
measured in the reflection experiment.
