Ultracompact SOI Microring Add–Drop Filter With Wide Bandwidth and Wide FSR

We report the design and fabrication of an ultracompact silicon-on-insulator add–drop microring filter with a 1.5- $\mu$m radius for wavelength-division-multiplexing on-chip interconnect applications. The fabricated device was measured to have a wide free-spectral range of 52 nm and a wide channel bandwidth of 210 GHz, with a 2.9-dB insertion loss and a deep through-port extinction of nearly 25 dB.