We propose and demonstrate a novel biosensor based on a silicon-single-microring-resonator-loaded Mach-Zehnder interferometer (MRR-MZI), and discuss the design of the sensor theoretically. Owing to the combination of an MZI and the enhanced phase change in a microring resonator (MRR), high sensitivity is expected to be realized. The designed MRR-MZI sensor is fabricated using a CMOS-compatible process, and its sensing characteristics are measured using ethanol solutions with a concentration of less than 3 wt % and avidin solutions. The sensitivity of the MRR-MZI to changes in the environmental refractive index is increased by approximately 50 times compared with that of a simple MRR. In addition, avidin solution with a concentration as low as 20 pM was successfully detected.

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Winter 2004tokyo -Having just strolled down the incline from Fumihiko Maki's serene Hillside Terrace complex of apartments and shops, I had architecture on my mind. Looking for a place to sit and read the morning papers, I followed the aroma to a cafe near the bustling entrance of a substation on the Shibuya line. Whether it's the attention to detail, the high-tech machines or perhaps the quality of the beans and water, I've always found the best coffee outside of Italy in Japan.