Microring resonator arrays for multiparameter biochemical analysis

We have recently demonstrated a particularly economic approach to analyze large arrays of microring resonator (MRR) sensor elements coupled to a single bus waveguide. The sensor elements can be individually functionalized to specifically promote the accumulation of target molecules. The binding of target molecules to the surface of a particular MRR results in an increase of its resonance wavelengths which can be measured with high accuracy. In order to measure the response of the individual MRR from an array to external stimuli, we employ a special frequency modulation scheme in which each MRR is independently modulated and phase sensitive lock-in detection is used to filter the respective frequency component from the superimposed complex transmission spectrum of the bus waveguide. We fabricated test arrays comprising up to 12 MRR coupled to a single bus waveguide. A silicon nitride based material system was chosen to realize the devices. Each element of an array is equ ipped with a platinum heater electrode for thermo-optical modulation. A tunable laser system was used for optical characterization and a clear readout of the individual MRR resonance frequencies was possible by employing the modulation scheme above. Furthermore, we demonstrated a bulk refractive index sensitivity of 190 nm/RIU for a frequency modulated MRR. With our first results, we point out the large potential for multiplexed label-free detection of diverse bio molecular compounds. Due to the miniaturization of the multisensor arrays the realization of portable sensor systems will be feasible.