Photo-controlled deformable mirror for wavefront shaping

Abstract

Wavefront shaping is of main interest in the field of Adaptive Optics for Astronomy, wide-field imaging in Microscopy and live cells/tissues imaging in Biology. We propose an innovative technology for a new type of membrane deformable mirror, made by coupling a reflective polymeric membrane with a monolithic non-pixelated photoconductive substrate. The device is called continuous photocontrolled deformable mirror (PCDM), actuated by sending a light flux with given shape and intensity distribution, on the back side of the photoconductor, opposite to the reflective side. Unlike the other actuation mechanisms, this allows to obtain a continuous actuation field, without the typical segmented actuators pattern. Furthermore, it leads to a strong simplification to the driving electronics, for example by eliminating hundreds of cables used for the deformation control. Fundamental is the role played by the photo-excitation dynamics of the photoconductive material, in fact the deformation is obtained through the electrostatic pressure exerted by the photo-generated charge carriers, on the thin reflective membrane.We have developed a device with a single crystalline semiconductor photoconductor wafer, either Silicon or Cadmium Sulfide. The actuation is controlled by a light pattern modulated by a DMD (Digital Micromirror Device) chip, generating a reprogrammable actuator pattern projected on the photoconductor. In order to test the performance of the PCDM, we are addressing two deformation regimes: static behavior and dynamical response. We are then able to measure the response with light actuation, as the influence function matrix with respect to the number of projected virtual actuators; the response with frequency, including response time, resonance frequency, with respect to the different applied patterns, and with respect to the number of virtual actuators; finally, the response in open/close loop.

Silicon based photo-controlled deformable mirror

“…The main features of the Shack-Hartman device are reported in Table 3. The scheme of the optical set up is reported in Figure 5 and described in [25]. The PCDM was fed with an AC voltage obtained by the combination of a function generator (Voltcraft FG8210) and a voltage amplifier (Falco Systems WMA-100).…”

Demonstration of magnetic and light-controlled actuation of a photomagnetically actuated deformable mirror for wavefront control

“…Photocontrolled deformable mirrors (PCDMs), where actuation is varied by the intensity of incident light rather than current or voltage, allow optical addressing with the potential for high-density remote control. Several authors have proposed PCDMs [37][38][39][40] employing a photo-conductive substrate to vary the voltage applied to a membrane mirror.…”