Polarization Analysis of Vertically Etched Lithium Niobate-on-Insulator (LNOI) Devices
Chenyu Wang,
Yuchen Liu,
Jingyuan Qiu,
Zhilin Ye,
Dongjie Guo,
Mengwen Chen,
Zhijun Yin,
Xiao-Hui Tian,
Hua-Ying Liu,
Shi-Ning Zhu,
Zhenda Xie
Affiliations
Chenyu Wang
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Yuchen Liu
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Jingyuan Qiu
NanZhi Institute of Advanced Optoelectronic Integration Technology Co., Ltd., Nanjing 210018, China
Zhilin Ye
NanZhi Institute of Advanced Optoelectronic Integration Technology Co., Ltd., Nanjing 210018, China
Dongjie Guo
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Mengwen Chen
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Zhijun Yin
NanZhi Institute of Advanced Optoelectronic Integration Technology Co., Ltd., Nanjing 210018, China
Xiao-Hui Tian
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Hua-Ying Liu
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Shi-Ning Zhu
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
Zhenda Xie
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
LNOI devices have emerged as prominent contributors to photonic integrated circuits (PICs), benefiting from their outstanding performance in electro-optics, acousto-optics, nonlinear optics, etc. Due to the physical properties and current etching technologies of LiNbO3, slanted sidewalls are typically formed in LNOI waveguides, causing polarization-related mode hybridization and crosstalk. Despite the low losses achieved with fabrication advancements in LNOI, such mode hybridization and crosstalk still significantly limit the device performance by introducing polarization-related losses. In this paper, we propose a vertically etched LNOI construction. By improving the geometrical symmetry in the waveguides, vertical sidewalls could adequately mitigate mode hybridization in common waveguide cross sections. Taking tapers and bends as representatives of PIC components, we then conducted theoretical modeling and simulations, which showed that vertical etching effectively exempts devices from polarization-related mode crosstalk. This not only improves the polarization purity and input mode transmittance but also enables lower polarization-related losses within more compact structures. As a demonstration of fabrication feasibility, we innovatively proposed a two-step fabrication technique, and successfully fabricated waveguides with vertical sidewalls. Such vertical etching technology facilitates the development of next-generation high-speed modulators, nonlinear optical devices, and other advanced photonic devices with lower losses and a smaller footprint, driving further innovations in both academic research and industrial applications.
