8-Channel CWDM Filter on the Lithium-Niobate-on-Insulator Platform Using Cascaded Multimode Waveguide Gratings

An 8-channel coarse-wavelength-division multiplexing device is realized on lithium-niobate-on-insulator platform. The experiment result exhibits box-like spectral responses with ~20 nm channel spacing, 1-dB bandwidth $\sim$ 13-16 nm, and low inter-channel-crosstalk $< -22\text{dB}$ for all channels.