  Materials of which the optical response is determined by their structure are
of much interest both for their fundamental properties and applications.
Examples range from simple gratings to photonic crystals. Obtaining control
over the optical properties is of crucial importance in this context, and it is
often attempted by electro-optical effect or by using magnetic fields. In this
paper, we introduce the use of light to switch and tune the optical response of
a structured material, exploiting a physical deformation induced by light
itself. In this new strategy, light drives an elastic reshaping, which leads to
different spectral properties and hence to a change in the optical response.
This is made possible by the use of liquid crystalline networks structured by
Direct Laser Writing. As a proof of concept, a grating structure with
sub-millisecond time-response is demonstrated for optical beam steering
exploiting an optically induced reversible shape-change. Experimental
observations are combined with finite-element modeling to understand the
actuation process dynamics and to obtain information on how to tune the time
and the power response of this technology. This optical beam steerer serves as
an example for achieving full optical control of light in broad range of
structured optical materials.
