Research/MEMS Tunable Wavelength Selective Filter

Mirror cubes on MEMS†

Best performance of optical reflector could be found with the dielectric coated glass cube mirror in a thick plate form. It is indeed possible to have such films deposited on a MEMS structure but with a risk of deformed mirror surface due to the intrinsic residual stress. We have newly invented a way of mounting a pair of parallel mirror cubes onto a MEMS electrostatic platform; one of the mirror cube is displaced in a micron scale to tune the optical interference cavity of the Fabry-Perot interferometer. The device is used as a tunable wavelength filter for the WDM (wavelength division multiplex) fiber optic telecom.

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Wavelength tuning capability†

By tuning the air gap between the mirror cube, the center wavelength of the transmission is controlled within the 1.55 micron wavelength range. Thanks to the electrostatic comb-drive actuator's performance, the wavelength tuning is pretty linear with the drive voltage.

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Optomechanical performance†

Despite the surface-to-surface contact between the flat mirrors, the air gap could be easily controlled by the electrostatic actuation without causing permanent stiction. See the following journal report for more information.

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Reference†

This work has been conducted in collaboration with Koshin Kogaku Co., Ltd., Japan.
T. Yamanoi, T. Endo, and H. Toshiyoshi,, A hybrid-assembled MEMS Fabry-P´erot wavelength tunable filter, Sens. Actuators A: Phys. (2007), doi:10.1016/j.sna.2007.10.080