Differential Optical Sensing through Coupled Micro Ring Resonators

We theoretically investigate the performance of a double micro ring resonator for integrated optical sensing applications. The transmission characteristics of the proposed device can be driven in two distinct operations by controlling the difference of the round-trip phase shifts of the coupled resonators. The enhancement of the limit of detection by a factor of 5.6 compared to a single micro ring based sensor is demonstrated. Beside the fact that the single and double ring based schemes have the same spectral wavelength sensitivity of 918 nm per refractive index unit, the latter scheme also supports the intensity interrogation which can be used for on-chip thermal noise compensation via integrated micro heaters.