Optimization of electrode geometry and piezoelectric layer thickness of a deformable mirror

Alexey V Kruchenko,Kateřina Nováková,Pavel Mokrý,Miroslav Šulc,Vít Lédl,Marek Škereň,Václav Kopecký,Radek Melich

doi:10.1051/epjconf/20134800011

Abstract

Deformable mirrors are the most commonly used wavefront correctors in adaptive optics systems. Nowadays, many applications of adaptive optics to astronomical telescopes, high power laser systems, and similar fast response optical devices require large diameter deformable mirrors with a fast response time and high actuator stroke. In order to satisfy such requirements, deformable mirrors based on piezoelectric layer composite structures have become a subject of intense scientific research during last two decades. In this paper, we present an optimization of several geometric parameters of a deformable mirror that consists of a nickel reflective layer deposited on top of a thin lead zirconate titanate (PZT) piezoelectric disk. Honeycomb structure of gold electrodes is deposited on the bottom of the PZT layer. The analysis of the optimal thickness ratio between the PZT and nickel layers is performed to get the maximum actuator stroke using the finite element method. The effect of inter-electrode distance on the actuator stroke and influence function is investigated. Applicability and manufacturing issues are discussed.

Highlights

In the middle of the last century, the resolution of terrestrial astronomical telescopes reached such limits that further improvement of their resolution required a development of methods for the correction of atmospheric distortions
In order to increase the number of degrees of freedom, deformable mirrors based on piezoelectric unimorphs or bimorphs have become a very popular and intensively studied concept [4,5,6,7,8]. This type of the deformable mirror consists of a layered sandwich composite structure, where the reflective layer is bonded on a piezoelectric layer
Aforementioned issues have motivated the work presented below, where we will address the problem of the optimization of the composite structure of the deformable mirror to achieve the maximum out-of-plane deflections at minimum applied voltages to the piezoelectric structure using finite element method (FEM) numerical simulations

Summary

Introduction

In the middle of the last century, the resolution of terrestrial astronomical telescopes reached such limits that further improvement of their resolution required a development of methods for the correction of atmospheric distortions. Requirement of dense spacing of the actuators can be satisfied in small and medium size mirrors with many difficulties This type of the deformable mirror consists of a layered sandwich composite structure, where the reflective layer is bonded on a piezoelectric layer. By applying a voltage to a particular electrode, the piezoelectric layer is deformed due to the inverse piezoelectric effect in the in-plane directions This produces bending moments in the reflective layer of the particular segment of a deformable mirror and yield its out-of-plane deformation (see Fig. 1). Aforementioned issues have motivated the work presented below, where we will address the problem of the optimization of the composite structure of the deformable mirror to achieve the maximum out-of-plane deflections at minimum applied voltages to the piezoelectric structure using finite element method (FEM) numerical simulations.

Geometry of the deformable mirror

FEM model of the deformable mirror

Results and discussion

Conclusions