Heterogeneous integration of microelectromechanical system (MEMS) and electro-optical (EO) polymers waveguide modulator

This thesis presents the modeling, design, fabrication and testing of a MEMS-based bias element integrated into an electro-optical polymer modulator. In contrast to a conventional Mach-Zehnder (MZ) modulator which uses an electrical bias, the MEMS-based approach resolves the voltage drift problem and avoids the use of additional external circuitry which limits the available bandwidth. The desired phase bias of the optical signal is achieved by deflecting and elongating the optical path using electrostatic parallel plate actuators. By taking advantage of the pull-in effect of the flexible actuator, large forces can be generated at moderate applied voltages.; Three modeling methods are presented: (1) an analytical solution based on beam theory to model the polymer strip which contains the optical waveguide; (2) a simplified semi-analytical model using beam theory for the polymer and the electrostatic parallel plate equation to model an gap-closing actuator; and (3) a three-dimensional finite element approach adopting the electrostatic force equation into the purely mechanical model to simulate the entire system. Predictions based on these modeling methods are compared with experimental results, showing that these tools provide reasonable accuracy for the response of the as-built devices.; Test devices have been fabricated by surface micromachining techniques. The detailed fabrication process involving the successful heterogeneous integration process of MEMS actuators and polymer structure is presented. This process uses polycrystalline germanium as the sacrificial layer instead of the more common silicon dioxide in order to prevent damage to the polymer when the MEMS structural elements are released.; Experimental results confirm the feasibility of the MEMS-based approach in the aspects of the integration process and the replacement of the electrical bias with the mechanical element.