Ring Laser Gyroscopes by MEMS Technology

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In this research project, we have established basic technologies for MEMS-based Ring Laser Gyroscope (MEMS RLG). At first, we newly suggested an optical closed-loop by (111) mirror which results from wet anisotropic etching of single crystalline silicon-wafer with (110) surface orientation. The optimum etching condition, effect of miss-alignment, etc. were investigated and we found that the (111) mirror have sufficient quality for an optical mirror at the optimum conditions. Other required optical elements such as lenses and prisms were realized by photo-sensitive epoxy resin and their optical characteristics were examined and confirmed that they are useful for optical-devices. Moreover, alignment and clumping structures for laser diode chip were also constructed by this resin. Then, we combine the mirror fabrication-process and epoxy-resin based process in batch manner, which enables mass production and low cost. In order to improve reflectance of the mirror, we developed direct gold-electroplating technique for silicon surface. This technique eliminates the complicated process to deposit a metal film to the each mirrors by sputtering or evaporation. Many numbers of techniques mentioned above are very useful not only for MEMS RLG but for many devices in optical MEMS field. Now, we have a plan of collaboration with some industries to develop the MEMS RLG which can be put on the market.