Silicon-on-Insulator Microphotonic Resonators for Label-Free Biosensing: An Experiment-Based Comparison Between the Different Configurations

Abstract

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, showing that the slotted ring performs better than competitive approaches. A silicon photonic chip including tens of ring resonators was fabricated and optically characterized considering air and aqueous solutions as cladding. The best sensitivity achieved was 64nm/RIU for the slotted ring configuration. The ring displayed a Q-factor in the order of 2.57 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> , and the best estimated resolution was in the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–4</sup> RIU in water. The measured figure-of-merit was grater than 200RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–1</sup> .