Highly-sensitive sensor with large measurement range realized with two cascaded-microring resonators

A highly-sensitive sensor consisting of two cascaded-microring resonators (MRR) is suggested and investigated theoretically. The two MRRs are based on nanoslot waveguides and Si nanowires. By appropriately choosing the parameters, the MRR-based on nanoslot waveguides has a high sensitivity. The other MRR-based on Si nanowires is designed to have a large free spectral range (about 38 nm) and consequently a large measurement range (though its sensitivity is low). In this way, a highly-sensitive sensor with a large measurement range is achieved theoretically from the output spectral response from the bus waveguide of the two cascaded-MRRs. In order to make the design flexible and compact and reduce the crosstalk, the two drop waveguides for the cascaded-MRRs are perpendicular to the horizontal input bus waveguide.