Abstract
Variable Optical Attenuator (VOA) applied to control the optical signal intensity is an important device for the transceiver/receiver in optical communication system. In this thesis, a low voltage, no overshoot and anti-impact MEMS VOA would be implemented by MEMS technologies. Rotary comb drive was chosen as the actuator of VOA to prevent impact because its rigidity in rotation direction was much smallr than that in XYZ directions. However, rotary comb drive had high driving voltage. Serpentine spring with low spring constant could help to reduce the driving voltage. Considering the equivalent of mechanical and electrostatic torques, the device parameters were designed to achieve 20 rotation in 5V. Four optical attenuations (cantilever-type, pendulum, tilted, and folded micromirrors) were also devised to have maximum attenuation >40dB in 20 rotation by using TracePro simulation tool. Mask layout and fabrication followed the device design. SOI micromachining developed the device main structure. Then Au sputter process made the micromirror reflection. Finally, we measured the deices after fabrication completed. In this thesis, the design, fabrication, and measurement were accomplished. The MEMS VOA implemented could operate in 5V and have 400Hz bandwidth. Its step response showed no overshoot. The Tilted Micromirror design attenuated to maximum 55dB. The optical dynamic response <3ms, insertion loss=0.95dB, PDL=0.3dB, and WDL (1510~1590nm)=0.87dB.