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. 2023 Nov 30;23(23):9538.
doi: 10.3390/s23239538.

Thermal Behavior of Biaxial Piezoelectric MEMS-Scanners

Laurent Mollard  1 , Christel Dieppedale  1 , Antoine Hamelin  1 , Gwenael Le Rhun  1 , Jean Hue  1 , Laurent Frey  1 , Gael Castellan  1
Affiliations

Thermal Behavior of Biaxial Piezoelectric MEMS-Scanners

Laurent Mollard et al. Sensors (Basel). .

Abstract

This paper presents the thermal behavior of non-resonant (quasi-static) piezoelectric biaxial MEMS scanners with Bragg reflectors. These scanners were developed for LIDAR (LIght Detection And Ranging) applications using a pulsed 1550 nm laser with an average power of 2 W. At this power, a standard metal (gold) reflector can overheat and be damaged. The Bragg reflector developed here has up to 24 times lower absorption than gold, which limits heating of the mirror. However, the use of such a reflector involves a technological process completely different from that used for gold and induces, for example, different final stresses on the mirror. In view of the high requirements for optical power, the behavior of this reflector in the event of an increase in temperature needs to be studied and compared with the results of previous studies using gold reflectors. This paper shows that the Bragg reflector remains functional as the temperature rises and undergoes no detrimental deformation even when heated to 200 °C. In addition, the 2D-projection model revealed a 5% variation in optical angle at temperatures up to 150 °C and stability of 2D scanning during one hour of continuous use at 150 °C. The results of this study demonstrate that a biaxial piezoelectric MEMS scanner equipped with Bragg reflector technology can reach a maximum temperature of 150 °C, which is of the same order of magnitude as can be reached by scanners with gold reflectors.

Keywords: 2D MEMS mirror; Bragg reflector; high optical power management; piezoelectric; thermal behavior.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
MEMS mirror, top view (left) and zoom on hinge and PZT arm (right).
Figure 2
Figure 2
Cross-section of scanner with Bragg reflector.
Figure 3
Figure 3
Scanner deformation of a Bragg reflector (n = 2) along the Z-axis near ambient temperature (30 °C).
Figure 4
Figure 4
Z deflection of the PZT arms decreases with increasing temperature.
Figure 5
Figure 5
Bragg (n = 2) mirror planarity at different temperatures. The mirror was scanned along its diagonal.
Figure 6
Figure 6
2D-scanning representation at 30 °C (black) and 150 °C (red).
Figure 7
Figure 7
Optical angle θe (normalized relative to angle measured at 30 °C) as a function of scanner temperature done with four identical mirrors.
Figure 8
Figure 8
Projected image of the four spots on the screen (left) and shift in the barycenter (X and Y) of the four spots (right).
See this image and copyright information in PMC

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