Grating-assisted micro-ring resonators for silicon dual mode filters

The high index contrast of SOI platform makes the microring resonator very sensitive also to small inaccuracies in the fabrication process. Even with a state-of-the-art technology, a spectral spreading of the resonance positions, which quickly deteriorates the response of the filter. An accurate control of the resonance frequencies is therefore a challenging issue, which generally requires further fabrication steps, complex algorithms and power consumption techniques. In this paper, the authors experimentally demonstrate the possibility to overcome this limitation, by reporting an SOI second order filter with self-tuned resonance frequencies, realized by means of a grating assisted microring resonators . The proposed devices are formed by placing a Bragg grating inside a microring resonators. Bragg gratings with different values of reflectivity, realized by both holes and lateral burst structures, have been investigated.