Compact Optical Add-Drop De-Multiplexers with Cascaded Micro-Ring Resonators on SOI

A four-channel integrated optical wavelength de-multiplexer is experimentally illustrated on a silicon-on-insulator (SOI) substrate. With the aid of cascaded micro-ring resonators, the whole performance of the wavelength de-multiplexer is improved, such as 3 dB bandwidth and channel crosstalk. Based on the transform matrix theory, a four-channel wavelength de-multiplexer with average channel spacing 4.5\pm0.5 nm (3 dB bandwidth \sim 2\pm 0.5 nm) is demonstrated at telecommunication bands. For each channel, the extinction at the adjacent channel is below -39 dB and the out-of-band rejection ratio is up to 40 dB. The channel dropping loss is below 5 dB in the five FSR spectral response periods (near 100 nm).