We demonstrate single mode-splitting in two types of microring resonators with Bragg gratings. In the first device type, gratings are periodically embedded to the inner wall of the microring resonator. By adjusting the reflection coefficient of the grating and the self-coupling coefficient between the waveguide and microring, experimental results show that the distance between the splitting dips can vary from 0 to more than 1 nm.
In the second device type, Bragg gratings break into two identical parts with a π phase shift between them. The center peak in the mode-splitting spectrum has a full-width at half-maximum of 0.1 nm. The spectra can also be a Fano-type transmission, when the phase shift deviates from π.