An Electrothermal Tip-Tilt-Piston Micromirror Based on Folded Dual S-Shaped Bimorphs

TitleAn Electrothermal Tip-Tilt-Piston Micromirror Based on Folded Dual S-Shaped Bimorphs
Publication TypeJournal Article
Year of Publication2009
AuthorsJia, K., S. Pal, and H. Xie
JournalMicroelectromechanical Systems, Journal of
Pagination1004 -1015
Keywordsbulk silicon micromachining, dynamic testing, electrothermal tip-tilt-piston micromirror, folded dual s-shaped bimorphs, frequency 336 Hz, frequency 488 Hz, micro-optomechanical devices, micromachining, micromirrors, optical design techniques, optical fabrication, optical testing, out-of-plane piston actuation, silicon-on-insulator, silicon-on-insulator wafer, size 1 mm, thermal response time, thin-film surface micromachining

This paper presents the design, optimization, fabrication, and test results of an electrothermally actuated tip-tilt-piston micromirror with a large optical aperture of 1 mm. The fabrication of the device is a combination of thin-film surface micromachining and bulk silicon micromachining based on silicon-on-insulator wafers. The device has 3-DOF of actuations, including rotations around two axes in the mirror plane, and out-of-plane piston actuation. The micromirror shows an optical scan range of plusmn30deg about both x- and y-axes and displaces 480 mum in the z-axis, all at dc voltages that are less than 8 V. Dynamic testing of the micromirror shows that the thermal response time of each actuator is about 10 ms. Resonant frequencies of the piston and rotation motion are 336 and 488 Hz, respectively. The unique structural design of the device ensures that there is no lateral shift for the piston motion and no rotation-axis shift for the rotation scanning. With the large tip-tilt-piston scan ranges and low driving voltage, this type of device is very suitable for biomedical imaging and laser beam steering applications.