A dual reflective electrothermal MEMS micromirror for full circumferential scanning endoscopic imaging - art. no. 688508

This paper reports the design, fabrication and measurements of a dual-reflective, single-crystal silicon based micromirror that can perform full circumferential scanning (FCS) for endoscopic optical coherence tomography (EOCT). In the proposed FCS-EOCT probe, two optical fibers are used to deliver light beams to either surface of the micromirror, which can rotate +/- 45 degrees (or 90 degrees) and thus a 180 degrees optical scanning is obtained from each mirror surface, resulting in full circumferential scans. A novel surface- and bulk-combined micromachining process based on SOI wafers is developed for fabricating the dual reflective micromirror. The single-crystal-silicon device layer of SOI wafers is used for mirror flatness, and A1 is coated on both sides for high reflectivity. With one light beam delivered to each mirror surface, full 360 degrees scans have been observed. Other measured data include the resonant frequency: 328Hz, radius of curvatures: 124 mm (front surface) and 127 mm (back surface), and the reflectances: 81.3% (front surface) and 79.0% (back surface).