Four-channel CWDM device on a thin-film lithium niobate platform using an angled multimode interferometer structure

A compact and high-performance coarse wavelength-division multiplexing (CWDM) device is introduced with a footprint of 2.1 mm × 0.02 mm using an angled multimode interferometer structure based on a thin-film lithium niobate (TFLN) platform. The demonstrated device built on a 400 nm thick x -cut TFLN shows ultra-low insertion losses of < 0.72 dB . Measured 3 dB bandwidths are 12.1 nm for all channels, and cross talks from adjacent channels are better than 18 dB. Its peak wavelength positions comply with the CWDM standard with a channel spacing of 20 nm. The filter bandwidth of the proposed CWDM device can be tuned by adjusting the structural parameters. This demonstrated CWDM device will promote future realization of multi-channel and multi-wavelength transmitter chips on TFLN.