Box-like filter response using multimode single-ring microresonators

In this work we suggest a new technique to form a box-like filter response using a single microring resonator. The new design is based on exploiting the multimode propagation in the ring. The technique is implemented in the case of a two-mode ring resonator for different designs. The obtained results show that the new designs allow getting 1 to 10 dB spectral width shape factor better than 0.4, as verified by the FDTD simulation at different wavelengths and for different spectral widths. This new design methodology opens the door for more compact optical filters with controlled box-like response.