Silicon Multimode Waveguide Grating Filter at 2 μm

A silicon-based on-chip add-drop optical filter is realized for the wavelength-band of 2μm by integrating a multimode waveguide grating (MWG) and a pair of two-channel mode (de)multiplexers. The realized add-drop optical filter has low loss and high sidelobe suppression ratio in a broad band, achieved by optimizing the corrugation depth, the apodization strength, as well as the grating length. The measurement results agree very well with the theoretical simulation results. The demonstrated ∼100μm-long MWG has a large 0.5 dB bandwidth of 6∼26 nm and a sidelobe suppression ratio of 22∼27 dB. The thermal-tunability of the present optical filter is also demonstrated experimentally, and the measured tuning efficiency is about 0.16 nm/mW.