High‐Performance Mode‐Multiplexing Device with Anisotropic Lithium‐Niobate‐on‐Insulator Waveguides

• Published in: Laser & photonics reviews Vol. 17; no. 5
• Main Authors: Zhao, Weike, Liu, Ruoran, Zhu, Mingyu, Guo, Zehao, He, Jianghao, Li, Hanwen, Pan, Bingcheng, Yu, Zejie, Liu, Liu, Shi, Yaocheng, Dai, Daoxin
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.05.2023
• Subjects: Anisotropy; Crosstalk; Lithium; lithium niobate; Material properties; mode (de)multiplexers; multimode photonics; multimode waveguide bends; Multiplexers; Multiplexing; Niobates; Nonlinear optics; Optical interconnects; Photonics; Thin films; Wave propagation; Waveguides
• ISSN: 1863-8880; 1863-8899
• DOI: 10.1002/lpor.202200774

Thin‐film lithium‐niobate photonics has attracted intensive attention due to its superior material properties. In particular, multimode lithium‐niobate photonics is becoming attractive for the applications of high‐capacity optical interconnects and high‐efficiency nonlinear optics. However, multimode manipulation in lithium‐niobate‐on‐insulator (LNOI) waveguides is not easy because there might occur some mode hybridness due to the vertical asymmetry as well as the material anisotropy. In this paper, high‐performance mode‐multiplexing devices with anisotropic LNOI waveguides are proposed, consisting of a multi‐channel mode (de)multiplexer and a sharp multimode waveguide bend (MWB). The mode (de)multiplexer is designed with Z‐propagation LNOI waveguides to avoid the mode hybridness. Meanwhile, the sharp MWB is designed to connect with a Y‐propagation waveguide, enabling access to the highest electro‐optic coefficient and second‐order nonlinear coefficient. The fabricated mode (de)multiplexer has a low excess loss less than 0.2 dB as well as low crosstalk less than ‐19 dB in the wavelength range of 1520–1600 nm. These high‐performance multimode photonic devices are useful for developing multimode LN photonics. High‐performance mode‐multiplexing devices are demonstrated with anisotropic lithium‐niobate‐on‐insulator (LNOI) waveguides. The mode (de)multiplexer is designed with Z‐propagation LNOI waveguides to avoid the mode hybridness. Meanwhile, the sharp multimode waveguide bend is designed to connect with a Y‐propagation waveguide, enabling access to the highest electro‐optic coefficient and second‐order nonlinear coefficient. These multimode photonic devices are useful for developing multimode LN photonics.