Novel ring resonator based biosensors

Label-free photonic biosensors can perform sensitive and quantitative multiparameter measurements on biological systems and can therefore contribute to major advances in medical analyses, food quality control, drug development and environmental monitoring. Additionally they offer the prospect of being incorporated in laboratories-on-a-chip that are capable of doing measurements at the point-of-care at an affordable cost. A crucial component in most of these photonic biosensors is a transducer that can transform a refractive index change in its environment to a measurable change in its optical transmission. Silicon-on-insulator is a material system with many assets for such transducers. First, it has a high refractive index contrast permitting very compact sensors of which many can be incorporated on a single chip, enabling multiplexed sensing. Second, silicon-on-insulator photonic chips can be made with CMOS-compatible process steps, allowing for a strong reduction of the chip cost by high volume fabrication. By using ring resonators with high quality factors that have very narrow resonance peaks, the smallest detectable spectral shift can be minimized.