Optical microelectromechanical system development for biomedical imaging and fibre-optic switches

The application of micromachined devices is a growing area of interest in many domains, especially in the biomedical and telecommunication communities. In the biomedical community, advanced technology is now becoming available to produce medical instrumentation that is lightweight, compact, reliable, and requires low power. One of the most useful micromachined devices that could be used in the medical instrumentation is the micromachined mirror. Micromachined mirrors have small wobble and jitters, provide high scanning speed and accuracy, and are capable of precision positioning. These qualities are highly desirable for high performance scanners for biomedical imaging systems.; Another application of these micromachined mirrors is in telecommunication networks. Micromachined optical switches have been demonstrated to have lower polarization dependent loss (PDL), bit-rate and protocol independency, lower insertion loss, and lower crosstalk than guided-wave solid-state switches. When compared to their conventional counterparts, the lower losses of the micromachined switches allow them to be expandable to larger port-counts. In addition, micromachined optical switches have the potential to be more cost-effective because of batch fabrication techniques. They are also smaller in size and lighter in mass, thus allowing high-density packing on a single silicon substrate.; In this dissertation, two optical micromachined devices have been developed: (i) micromachined two degree-of-freedom (DoF) scanner for biomedical imaging; and (ii) 2-dimensional (2-D) micromachined optical switches for telecommunication networks. Each of the micromachined devices involves micro mirrors that are designed for each respective application.; The proposed two-DoF scanner requires low driving voltage for large angular scans, which is ideal for in vivo biomedical scanning. The structure of the scanner consists of a mirror plate and two attraction plates. It is the largest free-space-suspending micromachined structure known to exist. A high yield fabrication process was developed to reliably fabricate the scanner. The dimensions of the mirror are 1000 μm x 1000 μm and the attraction plates have dimensions of 1400 μm x 1700 μm. The entire structure is suspended in free-space by two pairs of torsion bars of dimensions 1.1 μm x 6 μm x 200 μm, and is actuated electrostatically to move in 2-DoF.; A novel optical cross connect (OXC) architecture, L-switching matrix, for telecommunication networks was proposed. This new architecture lowers the losses experienced by the longest and shortest path length and improved uniformity of the losses among all ports. A silicon-on-insulator (SOI) based fabrication process is developed to realize the double-sided mirrors that are essential to the L-switching matrix architecture. Theoretical models of both devices were developed. Extensive experiments were performed to validate the derived theoretical models.