Electrical tracing-assisted dual-microring label‑free optical bio/chemical sensors

We propose and demonstrate a novel electrical tracing-assisted dual-microring resonator-based optical sensor system in silicon-on-insulator substrate. The system comprises one microring resonator-based sensing element and another microring resonator-based tracing element integrated with electrical controller. The resonance wavelength shift of sensing microring induced by the refractive index change is traced and determined by direct voltage supply of the electrical tunable tracing microring. Such optical sensing system eliminates the traditional wavelength-scanning method thus provide a cost effective sensing scheme. Proof-of-principle demonstration by testing polyelectrolyte multilayer shows the sensitivity of ~4.0 mW/ng∙mm-2 and the detection limit of ~5.35 pg/mm2.