High-aspect-ratio rotary polygon micromotor scanners

This paper describes a polygon micromotor scanner fabricated from single cr ystal silicon by deep reactive ion etching (DRIE) for in-plane scanning app lications. The scanner consists of an outer-rotor wobble micromotor with a 1.4-mm diameter, 200-mu m thick rotor. The outer-rotor design circumvents o ptical beam interference by wires or probes that provide electrical excitat ion to the motor. A variety of rotor polygon types were designed and fabric ated, including those with three, four, six, and eight facets. After fabric ation of the components, the scanners were assembled and operated for exten ded periods in room air using a typical drive signal of 60 V and achieving rotational speeds up to 58 rpm. The 1310-nm optical beam was reflected off the Al-coated sidewall of the polygon rotor using external optics, achievin g optical coupling efficiencies of -5.8 dB and a scan angle of 50-110 degre es depending on the number of facets employed. During dynamic optical measu rements, 1.8-mm diameter gradient-index (GRIN) lenses were used as optical elements, and a repeatable signal was detected indicating less than 0.5 deg rees misalignment of the reflective surface due to rotor wobble or tilt. (C ) 1999 Elsevier Science S.A. All rights reserved.