Optical sensors consisting of compact microcavities appear promising for bio/chemical analysis systems and medical diagnostics and are particularly suitable for the development of optofluidic lab-on-chips. Planar integrated and miniaturized photonic sensors which can be combined with microfluidic systems in large quantities on a wafer scale are particularly attractive due to their production possibilities. This article presents integrated optical refractometers and label-free biosensors based on low-loss deposited silicon microring resonators. The microrings are used for refractive index measurements of fluids and after functionalization for the immobilization of biomolecules. The sensors which are embedded in silicon glass stacks or polymer microfluidic channels are investigated for their sensitivity and detection limits. Conventional wavelength transmission measurements in the near infrared are used for the sensor characterization and a novel concept with a tunable micro ring transducer is investigated.
