Low-Actuation Voltage MEMS Digital-to-Analog Converter with Parylene Spring Structures.

We propose an electrostatically-actuated microelectromechanical digital-to-analog converter (M-DAC) device with low actuation voltage. The spring structures of the silicon-based M-DAC device were monolithically fabricated using parylene-C. Because the Young's modulus of parylene-C is considerably lower than that of silicon, the electrostatic microactuators in the proposed device require much lower actuation voltages. The actuation voltage of the proposed M-DAC device is approximately 6 V, which is less than one half of the actuation voltages of a previously reported M-DAC equipped with electrostatic microactuators. The measured total displacement of the proposed three-bit M-DAC is nearly 504 nm, and the motion step is approximately 72 nm. Furthermore, we demonstrated that the M-DAC can be employed as a mirror platform with discrete displacement output for a noncontact surface profiling system.

A bi-stable 2x2 optical switch monolithically integrated with variable optical attenuators.

This work presents the development of a novel micromachined 2x2 optical switch monolithically integrated with variable optical attenuators. The proposed device can be easily realized by a standard manufacturing process with single photo mask. The key to realizing this device by such a simple approach is the employment the split-cross-bar (SCB) configuration. With this configuration, the fabrication challenges and layout constraints for accommodating all the sub-components of this dual-function device can be completely eliminated. The monolithically-integrated system has four movable mirrors, two bi-stable mechanisms and six actuators. The switching of optical signals is achieved by moving the mirrors attached on the bi-stable mechanisms using four of the actuators. The attenuation of optical power is carried out by moving the mirrors using the other two actuators and the bi-stable mechanisms. Also, only simple in-plane motions are needed for these sub-components to achieve all the functionalities. In addition, the adaption of bi-stable mechanisms can reduce the power consumption and simplify the actuation scheme. The measured insertion losses for both channels are about 1.0~1.1 dB, and the cross-talk is less than -60 dB. The attenuation range is about 30 dB for a maximum applied voltage of 20 V. Also, the measured switching time is less than 4 ms.