Coupled add-drop ring resonator for highly sensitive sensing

We propose a coupled add-drop ring resonator configuration for highly sensitive sensing. We theoretically examine the asymmetric Fano lineshapes of the two output ports of the proposed structure. The sharpness and the asymmetricity of the Fano resonance are linked to the high sensitivity. We theoretically calculate the sensitivity of the proposed coupled add-drop ring resonator as a sensor. The sensitivities of the two ports of our configuration can achieve 799.4 / rad (drop port) and 503.7 / rad (through port) respectively. The performance of the proposed structure is enhanced by almost 20 times than that of the single ring resonator based add-drop interferometer by introducing the upper ring resonator. This proposed configuration enables highly sensitive, compact and stable sensors.