Spiral cavity si wire resonators as label-free biosensors

We demonstrate densely folded silicon wire waveguide ring resonator sensors for label-free biosensing. A spiral ring resonator sensor of 30 μm × 30 μm area has a quality factor of over 20,000, and a cavity length equivalent to a ring of a diameter of 130 μm. We show that extended cavity length increases the quality factor and improves the fabrication robustness of resonators. Real time monitoring of molecular binding resolves ~ 0.2% of a protein monolayer. © 2009 OSA.