Magnetic actuation of bending and torsional vibrations for 2D optical-scanner application

摘要

This paper deals with a magnetically actuated microresonator as a test device for Light deflection applications (optical scanners). 2D scanning of a laser spot was achieved with this device and an optical scanning window of nearly 24 degrees was attained. Giant magnetostrictive thin films are used. They present the novel feature to produce wireless actuation in both bending and torsional modes, which can be decoupled at the corresponding resonance frequencies. In addition, depending on working conditions (bias field, magnetization orientation), the ratio between bending and torsional responses can be adjusted over a very large scale. We show how this ratio can be fixed by two methods: (i) by an appropriate choice of the initial state of the magnetic thin film during its deposition, and (ii) by a DC magnetic field, which is applied during the device operation. The mechanical characterization of the cantilever is presented. Anharmonic behavior due to large deflections was obtained. This nonlinear behavior is lessened with a folded-type mechanical structure. Torsional deflections up to 23 mu m, corresponding to mechanical rotations of +/-5.9 degrees angles have been attained at a field as low as 3.5 mT, corresponding to only 2% of the anisotropy field. Bending deflection can be twice in similar conditions. (C) 2000 Elsevier Science S.A. All rights reserved. [References: 12]