Ultra-low expansion glass-ceramic is a kind of functional materials, which has been extensively researched and widely used in various aspects because of its high performance. This paper introduces the optical mechanism and research progress of glass-ceramic. Also the application in aerospace area as laser gyro, objects telescope is illustrated. In addition to this, the preparation methods and prospects of ultra-low expansion glass-ceramic is discussed.
A modified low-cost unimorph deformable mirror (DM) driven only by positive voltages for atmospheric turbulence compensation is presented. The 214 patterned inner actuators generate convex deformations for aberration correction, while one outer ring actuator generates an overall concave bias. To evaluate the aberration correction capability of the proposed DM, the iterative reconstruction of Zernike aberrations and correction were performed in an adaptive optics test system. The experimental results indicate that the fabricated DM has an excellent aberration correction capability, particularly matching the first 20 term Zernike aberrations with the normalized residual root-mean-square (RMS) error <5%. Furthermore, the random atmospheric turbulence aberrations were simulated based on Karhunen–Loève coefficients and reconstructed using the fabricated DM. The simulative and experimental results show that the atmospheric turbulence aberrations can be steadily compensated with λ/40 (λ=2.2 μm) RMS residual error, indicating the prospect for atmospheric applications.
This paper proposes a low-cost unimorph deformable mirror (DM) driven by positive voltages for ocular adaptive optics
(AO). The DM consists of an inner actuators array and an outer ring actuator. The inner actuators array is used to correct
aberrations, while the outer ring actuator is used to generate an overall defocus bias. The measurement results show that the
maximum peak to valley defocus deformation is more than 14 μm. The DM has a satisfactory correction capability for up
to the fifth order Zernike mode aberrations. Furthermore, a sample of 200 ocular wavefronts was simulated using a
statistical model developed by Thibos. After correction with the developed DM, most of the simulated eyes achieved the
diffraction-limited performance. These experimental and simulation results indicate that this DM is satisfactory for ocular
Once a laser beam suffers from wavefront aberrations, the intensity of the focal spot degrades and the shape of
the focus spot distorts. The same problem also exists in femtosecond laser fabrication system. The aberrations in the
femtosecond laser fabrication system contain two main components: system aberrations and aberrations from the
refractive index mismatch problem. Recently, adaptive optics (AO) has been used for laser beam aberrations correction
to improve the light beam quality. In this paper, we introduce an adaptive optics system with double drive modes
unimorph deformable mirror (DM) into the femtosecond laser fabrication system. In the experiments, the hill-climbing
algorithm based on Zernike modes is used to control the DM to correct the aberrations in the close-loop manner. After
correction for system aberrations and the refractive index mismatch aberrations, the shape and maximum intensity of the
focal laser spot is much improved.
Unimorph deformable mirrors are attractive in adaptive optics system due to their advantages of simplicity, compact, low cost and large stroke. In this paper, a double drive modes unimorph deformable mirror is presented, which comprises a 200 μm thick PZT layer and a 400 μm thick silicon layer. This deformable has 214 inner actuators in the 50-mm active aperture, which are for the aberration correction and a outer ring actuator for generating an overall defocus bias. An analytical model based on the theory of plates and shells is built to predict the behavior of the deformable mirror. The stroke of the deformable mirror is tested in the experiments. In order to test the performance for aberration correction, the deformable mirror is used to correct the aberration from its imperfect initial mirror surface in the close-loop manner. The root-mean-square value of the mirror surface after the close-loop correction for ten iterations is about λ/40, which indicates this deformable mirror has a good aberration correction performance. This DM has the potential to be used for astronomical adaptive optics.
Unimorph deformable mirrors are attractive in adaptive optics system due to their advantages of simplicity, compact, low
cost and large stroke. In this paper, a double drive modes unimorph deformable mirror is discussed, which comprises a
100 μm thick PZT layer and a 200 μm thick silicon layer. This deformable mirror (DM) can achieve two different
directions deformation of concave and convex driven by only positive voltage. The dual direction maximum defocus
deformations are -14.3 μm and 14.9 μm. The close-loop performance of this DM is also tested in an experimental
adaptive optics system based on Hartman-Shack wavefront sensor. In experiments, the DM is controlled by the steepest
descent algorithm (SD) to corrected the aberrations in a close-loop manner. The ability of this DM of correction for the
system aberration and reconstruction for the low order Zernike mode aberration is tested. The root mean square (rms)
value of the system aberration after close-loop correction is about 28 nm. The reconstruction results for most low order
Zernike mode aberrations have a relative error less than 10%.