Design and characterization of slit variable microgratings

This paper presents the design, modeling, fabrication, and characterization of two novel slit variable gratings using silicon-on-insulator (SOI) technology. These two electrostatic SOI-based slit variable gratings were named as serpentine shape grating (SSG) and bridge shape grating (BSG), respectively. The key components of SSG are a deformable serpentine-shaped beam interleaved with eight fixed cantilevers. The slit spacing of SSG is variable by electrostatically induced deformation of the serpentine-shaped beam. Electrostatically actuated BSG consists of 48 beams, acting as rulings, with different spring constants, varying periodically. The BSG grating can be adjusted due to different ruling displacements resulting from different spring constants. Using the finite element analysis (FEA) packages (ANSYS and Intellisuite), the two designs were optimized for a combination of large deflections at low actuation voltages. The optical beam propagation analysis was performed to demonstrate the optical performance of the microgratings using Rsoft. The preliminary electromechanical testing result proves that a 0.2-μm deflection is reached with the actuation voltage less than 3.5 V for both the two slit variable gratings, which shows good agreement with the FEA models. The two designs have the advantages of not requiring the bottom electrodes under the gratings to be segmented by comparison with existing slit variable gratings, and the extremely low actuation voltages present compatibility with the novel emerging SOI technology.