Research on fabrication of micro-optical resonators that can enclose light

As part of a project to commemorate the 75th anniversary of Keio University’s Faculty of Science and Technology, the University has started an innovative research project involving the industrial, government, and academic sectors. This project is called the Keio Innovation Foundry, or KIF. Its participants have formed a consortium, to co-develop technologies from the Faculty of Science and Technology that are close to having commercial applications. The aim is to pursue a diverse range of joint research, with lively interchange among researchers in all three sectors.
Associate Professor Kakinuma belongs to the Department of System Engineering, which has begun research activities as a KIF project. Professor Kakinuma is doing research on micro-optical resonators, which have the ability to enclose light in a specific place for a specific time. His research focuses on processes for fabricating themselves, and on improving their performance.
Q. These small containers, called micro-optical resonators, could be utilized in applications such as next-generation devices with ultra-low energy consumption. For example, they’ll constitute an essential technological component of next-generation devices such as optical memory. Before starting this KIF project, I worked on a project called the Keio Next-Generation Research Promotion Project, with Professor Tanabe in the Department of Electronics and Electrical Engineering. That was the first time I did joint research with Professor Tanabe, and our goal was an entire research process, from making these micro-optical resonators to testing them. And now, we’re taking this research a further step ahead: As back-up from industry, the project now includes a manufacturer of ultra-precise machine tools.
As a material for achieving high-performance micro-optical resonators, single crystal fluorite is considered ideal. So, the researchers are analyzing the processing characteristics of single crystal fluorite in ultra-precision machining, from the viewpoint of crystal anisotropy.
Q. The fluorite which we focuses on is a single-crystal material, and it’s very difficult to process single crystals with nanoscale precision. But what we’ve found is that, if we process certain planes in certain directions, we can process the entire surface without breaking the crystal. By doing that, we’ve succeeded in forming fluorite into micro-optical resonators, just by cutting it with nanoscale precision. So, we’re moving ahead with our research while using this process. We’re analyzing the results in terms of the crystal structure, or the crystal orientation, and doing experimental research on how to achieve the processing effectively.
In this project, the ultimate goal is to fabricate micro-optical resonators that can enclose light for as long as possible, by making effective use of nano-precision machining technology. So, the research is subject to high hopes, both inside and outside Keio University.
Q. Cutting is a process that applies a load, and how sharply something can be cut depends on how extremely it has to be shaped. So, first of all, we’re investigating what level of shaping can be achieved by nano-machining. Right now, we’re very interested in that kind of scientific issue, so this investigation is our current topic. If we can clear that hurdle, we think this nano-machining technology could be developed as one method for fabricating micro-optical resonators.