Design and Fabrication of a 2-Axis Electrothermal MEMS Micro-Scanner for Optical Coherence Tomography †

This paper introduces an optical 2-axis Micro Electro-Mechanical System (MEMS) micromirror actuated by a pair of electrothermal actuators and a set of passive torsion bars. The actuated element is a dual-reflective circular mirror plate of 1 [Formula: see text] in diameter. This inner mirror plate is connected to a rigid frame via a pair of torsion bars in two diametrically opposite ends located on the rotation axis. A pair of electrothermal bimorphs generates a force onto the perpendicular free ends of the mirror plate in the same angular direction. An array of electrothermal bimorph cantilevers deflects the rigid frame around a working angle of 45 [Formula: see text] for side-view scan. The performed scans reach large mechanical angles of 32 [Formula: see text] for the frame and 22 [Formula: see text] for the in-frame mirror. We denote three resonant main modes, pure flexion of the frame at 205 [Formula: see text] , a pure torsion of the mirror plate at 1.286 [Formula: see text] and coupled mode of combined flexion and torsion at 1.588 [Formula: see text]. The micro device was fabricated through successive stacks of materials onto a silicon-on-insulator wafer and the patterned deposition on the back-side of the dual-reflective mirror is achieved through a dry film photoresist photolithography process.