Adaptive optics

Recent advances in adaptive optics have made the realization of deformable mirrors a subject of intense research. Following the local deformation of the mirror surface, deformable mirrors induce spatially controlled phase change on the reflected beam.
As an example, deformable mirrors used in adaptive optical systems allow measuring the distortion of an incident wavefront and accomplishing the correction of said distortion and the consequent shaping of the reflected beam.
Several schemes for optoelectronic deformable mirrors have been proposed up to now, based either on independently actuated juxtaposed rigid sections made of piezoelectric material, or on flexible large-area reflective membranes. The rigid sections or the elemental areas of the membrane act as independent reflective elements, and are driven by respective independent actuators, in order to carry out a local mirror deformation adapted to achieve a desired correction of the locally incident wavefront. These implementations, even though successful for some specific applications, especially in astronomy, present however several drawbacks, like the complexity of the electronic circuitry driving each pixel individually, the discretization of the deformation and the limited spatial resolution of the reflected images.
We have realized a photo-controlled deformable mirror, PCDM, that is fabricated from the association of a metalized membrane with a single non-pixellated photoconductive substrate. An ac voltage is applied across the PCDM. The impedance of the photoconductive substrate decreases when the incident illumination increases. When the voltage increases, the capacitive effect attracts the membrane towards the photoconductive substrate, hence, a membrane deformation is induced in the form of a paraboloid. Once the membrane has reached an equilibrium position, further deformations can be superimposed by local point illuminations


A novel device has also been realized and demonstrated to achieve the Mid-IR to near-IR image conversion by thermally induced optical switching in vanadium dioxide.Adaptive optics
Recent advances in adaptive optics have made the realization of deformable mirrors a subject of intense research. Following the local deformation of the mirror surface, deformable mirrors induce spatially controlled phase change on the reflected beam, thus acting as spatial light modulators. As an example, deformable mirrors used in adaptive optical systems allow measuring the distortion of an incident wavefront and accomplishing the correction of said distortion and the consequent shaping of the reflected beam.
Several schemes for optoelectronic deformable mirrors have been proposed up to now, based either on independently actuated juxtaposed rigid sections made of piezoelectric material, or on flexible large-area reflective membranes. The rigid sections or the elemental areas of the membrane act as independent reflective elements, and are driven by respective independent actuators, in order to carry out a local mirror deformation adapted to achieve a desired correction of the locally incident wavefront. These implementations, even though successful for some specific applications, especially in astronomy, present however several drawbacks, like the complexity of the electronic circuitry driving each pixel individually, the discretization of the deformation and the limited spatial resolution of the reflected images.
We have realized a photo-controlled deformable mirror, PCDM, that is fabricated from the association of a metalized membrane with a single non-pixellated photoconductive substrate. An ac voltage is applied across the PCDM. The impedance of the photoconductive substrate decreases when the incident illumination increases. When the voltage increases, the capacitive effect attracts the membrane towards the photoconductive substrate, hence, a membrane deformation is induced in the form of a paraboloid. Once the membrane has reached an equilibrium position, further deformations can be superimposed by local point illuminations
A novel device has also been realized and demonstrated to achieve the Mid-IR to near-IR image conversion by thermally induced optical switching in vanadium dioxide.