Highly Sensitive Intensity Detection by a Self-Interference Micro-Ring Resonator

A novel highly sensitive intensity detection method has been proposed based on a self-interference ring resonator, where it is obtained by introducing an additional interference sensing arm between two coupling regions in the conventional planar add-drop micro-ring resonator. By means of dissipative and dispersive coupling mechanisms, optical path length changes of sensing arm not only bring the shift in a resonant wavelength, but also result in the variation of the linewidth and extinction of the spectrum. Using the analytical expression of the transmittance, it is proved that this sensor can monitor optical path length changes of sensing arm with a theoretical detection limit (5.6 × 10 -3 nm) by measuring intensity variations at a certain transmission valley.