High-performance tri-wavelength (1.064/1.55/3.393 µm) wavelength division multiplexer on thin-film lithium niobate.

In this work, a tri-wavelength (1.064/1.55/3.393 µm) wavelength division multiplexer is proposed and demonstrated on the thin-film lithium niobate platform with cascaded structure of a single directional coupler and two asymmetric directional couplers. Experimental results reveal low insertion loss (< 1.3 dB) and high crosstalk suppression (< -22 dB) across all three wavelengths, highlighting significant potential for on-chip nonlinear wavelength manipulation, especially in mid-infrared difference-frequency generation.