Designing transparent piezoelectric metasurfaces for adaptive optics

Abstract

Simultaneously generating various motion modes with high strains in piezoelectric devices is highly desired for high-technology fields to achieve multi-functionalities. However, traditional approach for designing multi-degrees-of-freedom systems is to bond together several multilayer piezoelectric stacks, which generally leads to cumbersome and complicated structures. Here, we proposed a transparent piezo metasurface to achieve various types of strains in a wide frequency range. As an example, we designed a ten-unit piezo metasurface, which can produce high strains (ε₃ = 0.76%), and generate linear motions along X-, Y- and Z-axis, rotary motions around X-, Y- and Z-axis as well as coupled modes. An adaptive lens based on the proposed piezo metasurface was demonstrated. It can realize a wide range of focal length (35.82 cm ~ ∞) and effective image stabilization with relatively large displacements (5.05 μm along Y-axis) and tilt angles (44.02' around Y-axis). This research may benefit the miniaturization and integration of multi-degrees-of-freedom systems.

Fig. 1. Design of a PM to generate the desired motion modes.

a Designed elements of a PM. b Exploded figure of an (5 × 2) arrayed PM. The applied voltages and simulated deformations of (c) the linear motion along the X-axis (artificial 31-mode), (d) the linear motion along the Y-axis (artificial 32-mode), (e) the linear motion along the Z-axis (artificial 33-mode), (f) the rotary motion around the X-axis (α-mode), (g) the rotary motion around the Y-axis (β-mode), (h) the rotary motion around the Z-axis (γ-mode).

Fig. 2. Output performance for the desired motion modes as a function of the boundary structures and geometric dimensions of the PM by FEM simulation.

a The strain ε₃ variation of the PM as a function of the Young’s modulus of the boundary structures. b The strain ε₃ variation of artificial 33-mode with the boundary structures. (The insets show the boundary structures of PM₁ and PM₂.) c The strain ε₃ variation of artificial 33-mode with the geometric dimensions of the boundary structure. d Photograph of the boundary structure. The strain (ε_j, j = 1 and 3) variation of (e) artificial 31-mode and (f) artificial 33-mode with the geometric dimensions of the piezoelectric units for the PM. The rotation angle (α and γ) variation of (g) α-mode and (h) γ-mode with the geometric dimensions of the piezoelectric units for the PM. The insets show the geometrical diagrams and deformations of the simulated motion modes by using PM₂. The black arrows represent displacement directions. The electric field of 400 V/mm was applied on the soft PZT ceramics and [001]-poled PIMNT single crystals.

Fig. 3. Experimental verification of the PM with the vibration displacement responses.

a The experimental setup for measuring the output displacements of the PM. The simulated and experimental vibration displacements of the PM in (b) artificial 31-mode, (c) artificial 32-mode, (d) artificial 33-mode, (e) α-mode, (f) β-mode and (g) γ-mode (with LTR = 40) under different electric fields (from 0 V/mm to 800 V/mm) at 2 Hz.

Fig. 4. Schematic and structure of the PM-based ALENS.

a The overall structure of the PM-based ALENS. (The inset at top right gives the structure of PM.) b Exploded figure of the PM-based ALENS. c The photograph of the PM-based ALENS prototype.

Fig. 5. The designed PM-based ALENS and corresponding experiments for vibration responses.

a–f Pictures on the left are the simulated deformations, including top view and sectional view; Pictures in the middle are vibration amplitudes under different frequencies (from 1 Hz to 400 Hz); Pictures on the right are actuation characteristics under different electric fields (from 120 V/mm to 1600 V/mm), including focal lengths, actuation displacements and rotation angles. a The linear motion along the Z-axis (AF), b the linear motion along the X-axis, c the linear motion along the Y-axis, d the rotary motion around the X-axis (pitch), e the rotary motion around the Y-axis (yaw) and f the rotary motion around the Z-axis (roll).

Fig. 6. The PM-based ALENS based on the AF and OIS functions under the basic modes and coupled modes for spot motion variation.

Ray optics simulations (including ray tracing and spot diagram) and dynamic characteristics experiment of optical spot for (a) AF, (b) pitch, (c) roll, (d) in the coupled modes of the AF and pitch, (e) in the coupled modes of the AF and roll in the PM-based ALENS.