Nanophotonics for Lab-on-Chip Applications

Optical methods are the preferred measurement techniques for biosensors and lab-on-chip applications. Their key properties are sensitivity, selectivity and robustness. To simplify the systems and their operation, it is desirable to employ label-free optical methods, requiring the functionalization of interfaces. Evanescent electromagnetic waves are probing the optical properties near the interfaces, a few 100 nm deep into the sample fluid. The sensitivity of these measurements can be improved with optical micro-resonators, in particular whispering gallery mode devices. Q factors as high as 2x10 have been achieved in practice. The resulting narrow-linewidth resonances and an unexpected thermo-optic effect make it possible to detect single biomolecules using a label-free biosensor principle. Future generations of biosensors and labs-onchip for point-of-care and high-troughput screening applications will require large numbers of parallel measurement channels, necessitating optical microresonators in array format produced very cost-effectively.