We report on the remote control of the fine structure of a diffraction spot from optically induced dual gratings within a photosensitive polymer film. The material contains azobenzene in the polymer side chains and develops a surface relief under two-beam holographic irradiation. The diffraction of a polarized probe beam is sensitive to the orientation of the azobenzenes forming a permanently stored birefringence grating within the film. We demonstrate that the fine structure of the probe diffraction spot switches from Gaussian to hollow or hollow to "Saturn"-like structure by a change in polarization. This makes it potentially useful in photonic devices, because the beam shape can be easily inverted by an external stimulus.