Design and Simulation of Low-Loss Multimode B-spline Shaped Waveguide Crossing Based on Lithium Niobate on Insulator

We designed and simulated a B-spline modified multimode waveguide crossing based on lithium niobate on insulator assisted by Equilibrium optimizer. The results show that when the waveguide width is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.5{\mu}\mathbf{m}$</tex> and the wavelength is 1550 nm, the insertion losses in the Y-propagation are about 0.05 dB for TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>, 0.25 dB for TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf>, and 0.32 dB for TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>. In the Z-propagation, the insertion losses are about 0.07 dB for TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>, 0.21 dB for TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf>, and 0.32 dB for TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>. Additionally, the results demonstrate excellent crosstalk properties.