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.