Compact mode converters in thin-film lithium niobate integrated platforms.

Mode converters, crucial elements within photonic integrated circuits (PICs) designed for multimode optical transmission and switching systems, present a challenge due to their bulky structures in thin-film lithium niobate (TFLN) integrated platforms, which are incompatible with the compact and efficient nature desired for dense PICs. In this work, we propose TE-TE, TE-TE, and TE-TE mode converters in shallowly etched TFLN, within small footprints. The experimental results show that the insertion loss is 0.