Compact silicon microring-assisted directional couplers for optical signal processing applications

We propose and demonstrate a compact microring-assisted directional coupler in the silicon-on-insulator material system. An analytical model based on the strongly coupled mode theory shows that the device can be designed to have a wide range of spectral characteristics, including sharp asymmetric Fano line shapes, which can be used for WDM, switching, and sensing applications. The measured transmission spectra of the fabricated device with a 5-mum-radius microring resonator exhibited an asymmetric spectral response characteristic of the Fano resonance as predicted by the analytical model.