Fraunhofer Institute for Photonic Microsystems
- SEM micrograph of a microring resonator.
© Fraunhofer IPMS
With optical measurements, ultrasensitive sensors and short measurement times can be realised. The microring resonator is an optical sensor principle with very great potential for miniaturisation. With microring resonators, chemical bonds (gases, liquids) and various biological species such as proteins, DNA or viruses can be verified. In microring resonators, light from a bus-waveguide is coupled in to a closed ring structure through the evanescent field. If the phase of the light has a multiple of 2π following a complete round of the ring, then the result will be resonance, and a large amount of energy will be coupled in to the ring. Biological species in the vicinity of the ring will change the resonance conditions. This change can provide evidence of the presence of biological species. A dependable manufacturing technology which can realize structures in the range of 50 nm to 150 nm with reliability is necessary for highly sensitive microring resonators. The most cost-efficient nano-imprint technology is used to manufacture this type of microring resonators.
The use of microring resonators as biosensors requires a functionalization of the ring surface. To this end Fraunhofer IPMS scientists develop suitable technologies.