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 1 -TE 0 , TE 2 -TE 0 , and TE 3 -TE 0 mode converters in shallowly etched TFLN, within small footprints. The experimental results show that the insertion loss is 0.4 dB, 0.6 dB, and 0.5 dB for the compact TE 1 -TE 0 , TE 2 -TE 0 , and TE 3 -TE 0 mode converters, respectively, and these devices can be operated within a wide 1 dB bandwidth (BW) over 100 nm. This work facilitates the development of low -loss, broadband, and compact monolithically integrated photonic devices for future multimode communication networks in TFLN integrated platforms. (c) 2024 Optica Publishing Group