Lithium Niobate Waveguide Mode Converter Based on V-Shaped Silicon

Mode converter, achieving the mode conversion task from fundamental mode to higher-order mode, is a key component for the on- chip multimode transmission and mode division multiplexing transmission. Here, we propose an array of V- shaped silicon mode converter based on the thin film lithium niobate (TFLN) waveguide. The mode conversion structure is consisted of an array of V- shaped silicon, where it is deposited atop the TFLN waveguide. Based on such structure, we conduct detailed structural analyses and optimizations, where the required conversion length is only 11 mu m and the central wavelength is 1550 nm for the mode conversion from input TE0 mode to output TE1 mode. The mode conversion efficiency, crosstalk, and insertion loss are 96. 8%, - 28. 6 dB, and 0. 78 dB, respectively. We further extend the device structure and obtain the mode conversion from input TE0 mode to output TE2 mode in the same length, where the mode conversion efficiency, crosstalk, and insertion loss are 91. 3%, -14. 3 dB, and 1 dB, respectively. If we further extend the device structure, other higher- order modes can also be obtained. We believe the proposed device structure and scheme could benefit the multimode transmission for the TFLN waveguide and boost the development of photonic integrated components and circuits based on the TFLN platform.