SEMICONDUCTOR AND GLASS MICRO-RESONATORS

Abstract

In this thesis we have demonstrated the cascading of two photonic AND logic gates by using two symmetric semiconductor GaAs microring resonators. In addition, we have developed a new, low-cost method for fabricating glass microring resonators. In the first part of this work, we discuss the properties of microring resonators and describe the fabrication of semiconductor microring resonators by the research team of which I was a member. In the experiments on cascaded logic gates we launched one probe and pump beam into different input waveguides, respectively. The first ring works as a AND logic gate for probe and pump beams. The output beam from the first ring goes to the second ring. The second ring also work as a AND logic gate using the second pump to switch the beam coming from the first ring. We successfully demonstrated cascading two photonic logic gates by using two symmetric semiconductor GaAs microrings.

In the second part of this work, we extended our prior work on the fabrication of semiconductor microrings in a clean room to a purely mechanical method of glass microring fabrication. Many laboratories, including ours, lack the expensive facilities needed for the lithographic fabrication of microrings. And, a low-cost, high yield method of fabrication may have significant application in the development of disposable microring sensors. We have built up a complete mass=production capability based on glass capillary pulling and micro-polishing to fabricate glass microrings, because there were no available off-the-shelf systems available from industry at affordable prices.

This method of producing highly polished glass micro-resonators has many advantages, such as fast fabrication (≦6 weeks), high yield (≧50%) (percentage of devices w/o cracks on edge), low cost (no need to use costly facilities in a clean room), mass production (800~1200 devices per batch). The surface quality of glass resonators should be excellent because capillaries were made at high temperature ≧1000℃ and devices were polished by suspension slurry of 70 nm colloidal silica. Further measurements that are beyond our current capability are needed for final verification. If some fabrication steps could be optimized in the future, we estimate that the fabrication time could be within 2 weeks, the yield rate would be higher than 90 %, and the number of devices per batch could be more than 1,200. This innovative method opens a new path for microresonator fabrication at low cost and in fast mass production. In sensor applications where low cost and mass production could be important, our work is an important first step to making microring sensors inexpensive, if further work in characterizing them can be done. Glass microresonators can play a key role, for example, in gas sensors, chemical sensors, liquid sensors, biological sensors, and vibration sensors. Two appendices in this thesis list the most significant sub-systems of the whole system we designed and built for producing glass microring resonators. Designs and engineering drawings are also listed in Appendices.