A Lithium-Niobate Waveguide Directional Coupler for Switchable Mode Multiplexing

We propose a lithium-niobate optical waveguide asymmetric directional coupler for the realization of an electro-optically switchable mode (de)multiplexer. Our typical fabricated coupler, designed for (de)multiplexing the LP01 and the LP11a mode, provides a switching efficiency higher than 90% and the operation wavelength can be tuned over a wide range of ~240 nm by varying the driving voltage between -23 and +20 V. Our proposed switchable mode multiplexer could find applications as a wavelength-selective mode switch or a reconfigurable mode add-drop (de)multiplexer for mode-division-multiplexing networks.