Silicon-on-insulator microphotonic resonators for label-free biosensing: an experiment-based comparison between the different configurations
la Grasta, A., De Carlo, M., Ardoino, N., Favaretto, R., Labbé, F., Ding, Y., Passaro, V. M. N., Dell’Olio, F. (2024) IEEE Sensors Journal
Resonant label-free biosensors using silicon-on-insulator substrates represent a cutting-edge domain in optical sensing. These devices leverage the high refractive index contrast of silicon-on-insulator materials to create highly sensitive, compact sensors. They are crucial for real-time, precise biomolecular detection in healthcare diagnostics, environmental monitoring, and drug discovery, marking a significant stride in microphotonic technology and its practical applications.
Different ring-based resonant configurations have been explored in this context, but a definitive comparative assessment of them was previously lacking in the literature. In our work, we experimentally compare four different ring configurations in terms of figure-of-merit (FoM), showing that the slotted ring performs better than competitive approaches.
A silicon photonic chip including tens of ring resonators (RRs) was fabricated and optically characterized considering air and aqueous solutions as cladding. The best sensitivity achieved was 64 nm/RIU for the slotted ring configuration. The ring displayed a Q-factor on the order of 2.57 × 10⁴, and the best estimated resolution was on the order of 10⁻⁴ RIU in water. The measured FoM was greater than 200 RIU⁻¹.
