Thin Film Lithium Niobate 1xN Multimode Interference Splitters

This paper presents the design of different configurations of 1 xN multimode interference (MMI) splitters made of thin film lithium niobate (TFLN) waveguides. The proposed 1xN MMI beam splitters allow the connection between 1 input and N outputs with a single device, without the need of cascading multiple components. It is shown that the different output ports of the designed 1 xN MMI splitters (i.e. with $\mathrm{N}=3,5$, 7) exhibit a good uniformity of power at the N outputs (less than 0.71 dB for the worst case ($\mathrm{N}=7$)) and a constant phase shift, which is stable in the whole considered wavelength range. Moreover, the overall insertion loss for different number N of outputs is less than 0.1 dB at the wavelength $\lambda=1.55 \mu \mathrm{m}$. These performances make the proposed 1 xN MMI splitters promising as feeding components for Optical Phased Array (OPA).