Development of a Bimorph Deformable Mirror Driven by Positive-voltage Actuators at Edge

To improve the thermal stability of the deformable mirror, a bimorph deformable mirror driven by positive-voltage actuators at edge was proposed. The ring electrode of the deformable mirror was used to generate an overall defocus bias, while the discrete electrodes were used to correct the wavefront aberrations. The bidirectional deformation of the mirror can be realized by the positive voltage only, and the thermal deformation of the deformable mirror was low due to the symmetrical structure. The deformable mirror prototype was fabricated and tested. The test results show that the residual error of mirror surface after flattening is less than lambda/30 (lambda = 1 064 nm). The typical low order Zernike mode aberrations, such as astigmatism, defocus, trefoil and coma, are accurately reconstructed. The reconstructed amplitudes are 11.1 mu m, 9.7 mu m, 5.7 mu m and 4.2 mu m, with the normalized residual errors of 1%, 1%, 3. 3%, and 6%, respectively. In addition, non-diffraction Airy beam is generated experimentally, which shows the excellent reconstruction performance of the deformable mirror.