Cascaded silicon-on-insulator double-ring sensors operating in high-sensitivity transverse-magnetic mode

We demonstrate ultrahigh-sensitivity silicon photonic sensors based on two cascaded double-ring resonators operating in transverse-magnetic mode. Both wavelength interrogation and intensity interrogation methods are experimentally investigated and the sensitivities reached 24,300 nm/RIU and 2430 dB/RIU, respectively. We also show that the double-ring sensors can be simply cascaded to realize simultaneous detection of multiple species, which is very promising for low-cost array applications.