Abstract

Fiber-to-chip coupling is an essential issue for taking high-performance integrated photonic devices into practical applications. On a thin-film lithium niobate platform, such a high-performance coupler featuring low loss, large bandwidth, and polarization independence is highly desired. However, the mode hybridization induced by the birefringence of lithium niobate seriously restricts a polarization-independent coupling. Here, we propose and experimentally demonstrate a high-performance and polarization-diversity cantilever edge coupler (EC) with the assistance of a two-stage polarization splitter and rotator (PSR). The fabricated cantilever EC shows a minimal coupling loss of 1.06 dB/facet, and the fully etched PSR structure shows a low insertion loss (IL) of −0.62 dB. The whole polarization-diversity cantilever EC exhibits a low IL of −2.17 dB and −1.68 dB for TE₀ and TM₀ mode, respectively, as well as a small cross talk of <−15 dB covering the wavelength band from 1.5 µm to 1.6 µm. A polarization-dependent loss <0.5 dB over the same wavelength band is also obtained. The proposed fiber-to-waveguide coupler, compatible with the fabrication process of popular thin-film lithium niobate photonic devices, can work as a coupling scheme for on-chip polarization-diversity applications.

© 2023 Optica Publishing Group

Silicon nitride assisted tri-layer edge coupler on lithium niobate-on-insulator platform

Zhiguo Yu, Yuxiang Yin, Xingrui Huang, Donghe Tu, Hang Yu, Huan Guan, Lei Jiang, Wei Yan, and Zhiyong Li
Opt. Lett. 48(13) 3367-3370 (2023)

Low-loss grating coupler with a subwavelength structure on a thin-film lithium niobate substrate

Jing Huang, Nuo Chen, Kaizhong Chen, and Tao Chu
Opt. Lett. 49(2) 222-225 (2024)

Fabrication tolerant and broadband polarization splitter-rotator based on adiabatic mode evolution on thin-film lithium niobate

Ranfeng Gan, Lu Qi, Ziliang Ruan, Jie Liu, Changjian Guo, Kaixuan Chen, and Liu Liu
Opt. Lett. 47(19) 5200-5203 (2022)

Low-loss edge-coupling thin-film lithium niobate modulator with an efficient phase shifter

Pan Ying, Heyun Tan, Junwei Zhang, Mingbo He, Mengyue Xu, Xiaoyue Liu, Renyou Ge, Yuntao Zhu, Chuan Liu, and Xinlun Cai
Opt. Lett. 46(6) 1478-1481 (2021)

One-dimensional grating coupler on lithium-niobate-on-insulator for high-efficiency and polarization-independent coupling

Bin Chen, Ziliang Ruan, Kaixuan Chen, and Liu Liu
Opt. Lett. 48(6) 1434-1437 (2023)