基于薄膜铌酸锂的片上电光调制器研究

The next generation broadband optical communication network requires high bandwidth, low driving voltage, small footprint and integratable electro-optic modulator. Conventional iondiffused lithium niobite waveguides suffer from the low refractive index contrast between core and cladding, resulting in large optical modal volumes. As a result, the photonic structures are large and the radio-frequency electrodes have to be placed far away from the optical mode to prevent detrimental waveguide propagation loss, significantly reducing the electro-optic switching efficiency. The sub-wavelength waveguide based on thin film lithium niobate material has recently emerged as a promising candidate to shrink the optical modal volume and boost the electro-optic efficiency. Therefore, it is very suitable for the construction of the next generation of on-chip electro-optical modulator with small size, low driving voltage and high bandwidth. This project focuses on the development of high performance electro-optic modulators. The following major scientific issues will be investigated: (1)the mechanism of the interaction between optical wave and microwave in lithium niobate nano waveguide; (2) the mechanism of the coupling between lithium niobate nano waveguide and polarization-maintaining single-mode fiber. The physical model, scalable fabrication process and low-loss optical coupling scheme will be developed for electro-optical modulator based on thin-film lithium niobate material. Finnally, Thin film lithium niobate based electro-optic modulators will be carried out, and the parameters of these modulators will be quantified through high-speed electro-optic tests. The electro-optic modulator will exhibit an insertion-loss of <5 dB, half-wave voltage of <3V, electro-optic bandwidth of at least 40 GHz. The expected results will build a basis for the development of low-cost, high speed electro-optic modulation in the future, and contribute to the development of of China's next generation broadband optical communication network.

研制能满足下一代宽带光通信网络需求的高带宽、低驱压、小尺寸、可集成的电光调制器件具有重大的应用前景。基于新型薄膜铌酸锂材料平台的强限制亚波长波导可大大缩小金属电极与光波导之间的间距，增强了调制电场与光波的相互作用，因此非常适合用来构建小尺寸、低驱压、高带宽的下一代片上电光调制器。本项目以研制下一代片上电光调制器件为目标，围绕铌酸锂纳米波导中光载波与微波调制电场的作用机理和铌酸锂纳米波导与保偏单模光纤的高效耦合机理等核心科学问题开展研究，建立基于薄膜铌酸锂材料的电光调制器的物理模型、开展高效的电光调制器结构设计、突破铌酸锂纳米光子器件的制备难题，实现低损耗的光纤-芯片水平耦合，最终研制出高性能、小尺寸的薄膜铌酸锂电光调制器芯片，调制器带宽>40GHz，插入损耗<5dB，半波电压<3V。预期项目成果将为低成本、高速低驱压调制器芯片的研制及量产打下基础，为我国下一代宽带光通信网络的发展贡献力量。

本项目针对宽带光通讯、微波光子等应用需求，力求解决低半波电压高速电光调制器的研制问题，完成了调制器的物理机理分析、器件优化设计、器件制备工艺开发、器件封装与测试等研究内容；突破了高速率LNOI调制器中光与电磁场的耦合机理与器件结构设计、高效光耦合的技术方案和实现途径、与常规半导体工艺兼容的LNOI调制器芯片制备技术等关键技术；研制了高速薄膜铌酸锂电光调制器芯片、封装好的低半波电压电光调制器等原型样件，完成了对调制器的静态和高速电光特性的测试。项目完成了LNOI电光调制器芯片的设计、流片和封装，封装后器件的3dB工作带宽≥40GHz，1GHz时RF半波电压≤3V，光学插入损耗≤5dB，最大输入光功率为257mW。本项目的研究成果在指标上全面超越现有的体材料铌酸锂电光调制器，有望在下一代宽带光通信网络及微波光子设备中获得应用。