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. 2023 May 9;14(5):1019.
doi: 10.3390/mi14051019.

Biaxial Piezoelectric MEMS Mirrors with Low Absorption Coating for 1550 nm Long-Range LIDAR

L Mollard  1 , J Riu  2 , S Royo  2   3 , C Dieppedale  1 , A Hamelin  1 , A Koumela  1 , T Verdot  1 , L Frey  1 , G Le Rhun  1 , G Castellan  1 , C Licitra  1
Affiliations

Biaxial Piezoelectric MEMS Mirrors with Low Absorption Coating for 1550 nm Long-Range LIDAR

L Mollard et al. Micromachines (Basel). .

Abstract

This paper presents the fabrication and characterization of a biaxial MEMS (MicroElectroMechanical System) scanner based on PZT (Lead Zirconate Titanate) which incorporates a low-absorption dielectric multilayer coating, i.e., a Bragg reflector. These 2 mm square MEMS mirrors, developed on 8-inch silicon wafers using VLSI (Very Large Scale Integration) technology are intended for long-range (>100 m) LIDAR (LIght Detection And Ranging) applications using a 2 W (average power) pulsed laser at 1550 nm. For this laser power, the use of a standard metal reflector leads to damaging overheating. To solve this problem, we have developed and optimised a physical sputtering (PVD) Bragg reflector deposition process compatible with our sol-gel piezoelectric motor. Experimental absorption measurements, performed at 1550 nm and show up to 24 times lower incident power absorption than the best metallic reflective coating (Au). Furthermore, we validated that the characteristics of the PZT, as well as the performance of the Bragg mirrors in terms of optical scanning angles, were identical to those of the Au reflector. These results open up the possibility of increasing the laser power beyond 2W for LIDAR applications or other applications requiring high optical power. Finally, a packaged 2D scanner was integrated into a LIDAR system and three-dimensional point cloud images were obtained, demonstrating the scanning stability and operability of these 2D MEMS mirrors.

Keywords: 2D MEMS mirror; Bragg reflector; high power management; piezoelectric; quasi-static actuator.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Modal analysis of the mirror: (a) First resonance mode (1.51 kHz-pumping mode); second (b) and third (c) resonance modes (2.179 and 2.18 kHz–X/Y-rotational modes)–Design variant 1.
Figure 2
Figure 2
MEMS mirror top view.
Figure 3
Figure 3
Evolution of absorption (%) (a) and reflectivity (%) (b) of PVD Bragg bilayer mirror vs the number of Bragg bilayer–comparison with gold reflective layer.
Figure 4
Figure 4
Magnitude/optical angle (▲) and Phase shift (●) for the first (Vpp = 3 V) (a) and second and third (Vpp = 4 V) (b) resonant modes–design variant 1.
Figure 5
Figure 5
2D scanning representation of MEMS mirror with Bragg (n = 2) reflector-50 point per fast axis period–(a) Design variant 1:25 V voltage-600Hz fast/horizontal axis and 10 Hz ramp slow/vertical axis–(b) Design variant 3:20 V Voltage–200 Hz fast/Horizontal axis and 4 Hz ramp slow/vertical axis.
Figure 6
Figure 6
2D scanning representation of MEMS mirror with Bragg (n = 2) reflector-50 point per fast axis period–20 V voltage-200 Hz fast/horizontal axis and 4 Hz ramp slow/vertical axis-(a) Design variant 4; (b) Design variant 5.
Figure 7
Figure 7
FoM values previously reported in [3] (▲) and this work (formula image Bragg (n = 2) and formula image Gold reflector).
Figure 8
Figure 8
(a) Mirror packaging and (b) integration of the MEMS scanner inside Biaxial LIDAR system (Right).
Figure 9
Figure 9
(a) View of the scene, (b) reflected laser intensity at 1064 nm and (c) depth value image.
Figure 10
Figure 10
3D representation of the scene, Point Clouds.
See this image and copyright information in PMC

References

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