Compact Mode Converters in Thin-film Lithium Niobate Integrated Platforms

• JingJing Zhang, pengfei qiu, runyu He, XIAOXIAN SONG, ZiJie Dai, Yang Liu, Dong Pan, Junbo Yang, and Kai Guo
• received 03/25/2024; accepted 04/25/2024; posted 04/26/2024; Doc. ID 524739
• Abstract: 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 footpints.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 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.