Single-Crystal PMN-PT-Laminated Piezoelectric Scanning Micromirror for Laser Beam Scanning Applications

A new type of piezoelectric scanning micromirror using single-crystal lead magnesium niobate-lead titanate (PMN-PT) is presented in this article. The micromirror is designed for one-dimensional (1-D) scanning and has a large aperture with a 5-mm-diameter reflective surface. The micromirror has single-crystal PMN-PT plates directly laminated onto micromachined silicon cantilever structures, and two different device geometries with varying PMN-PT planar dimensions have been designed. Mechanical amplification structures are utilized to achieve a maximum optical scan angle of over 30° at a low driving voltage. Finite element analysis (FEA) was used to optimize the micromirror design, which was then fabricated using deep reactive ion etching (DRIE) of a silicon-on-insulator (SOI) substrate and lamination of separately prepared PMN-PT plates. The driving characteristics of the fabricated devices were measured using out-of-phase actuation of the two piezoelectric cantilevers with forward and backward frequency sweeps at various input voltages. An optical scan angle of 31.38° at 3.514 kHz with 4- Vpp input has been achieved with model A in an ambient environment. The scan angle sensing capability was tested using a single cantilever for actuation and the other for sensing, and a relatively linear relationship was observed between the optical scan angle and the sensor output voltage with a measured average sensitivity of 0.158 Vrms/°. The uniformity of the PMN-PT lamination process was verified by testing multiple samples. The maximum optical scan angle before device failure was also measured, which was 72° at 34- Vpp input at 3.843 kHz.