Zhang Yuning, Wu Jiayang, Yang Yunyi, Qu Yang, Jia Linnan, Moein Tania, Jia Baohua, Moss David J
Optical Sciences Centre, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia.
Centre for Translational Atomaterials, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia.
ACS Appl Mater Interfaces. 2020 Jul 22;12(29):33094-33103. doi: 10.1021/acsami.0c07852. Epub 2020 Jul 10.
Layered two-dimensional (2D) graphene oxide (GO) films are integrated with silicon-on-insulator (SOI) nanowire waveguides to experimentally demonstrate an enhanced Kerr nonlinearity, observed through self-phase modulation (SPM). The GO films are integrated with SOI nanowires using a large-area, transfer-free, layer-by-layer coating method that yields precise control of the film thickness. The film placement and coating length are controlled by opening windows in the silica cladding of the SOI nanowires. Owing to the strong mode overlap between the SOI nanowires and the highly nonlinear GO films, the Kerr nonlinearity of the hybrid waveguides is significantly enhanced. Detailed SPM measurements using picosecond optical pulses show significant spectral broadening enhancement for SOI nanowires coated with 2.2 mm long films of 1-3 layers of GO and 0.4 mm long films with 5-20 layers of GO. By fitting the experimental results with theory, the dependence of GO's Kerr nonlinearity on layer number and pulse energy is obtained, showing interesting physical insights and trends of the layered GO films from 2D monolayers to quasi bulk-like behavior. Finally, we show that by coating SOI nanowires with GO films, the effective nonlinear parameter of SOI nanowires is increased 16-fold, with the effective nonlinear figure of merit (FOM) increasing by about 20 times to FOM > 5. These results reveal the strong potential of using layered GO films to improve the Kerr nonlinear optical performance of silicon photonic devices.
将层状二维（2D）氧化石墨烯（GO）薄膜与绝缘体上硅（SOI）纳米线波导集成，通过自相位调制（SPM）实验证明了增强的克尔非线性效应。采用大面积、无转移、逐层镀膜方法将GO薄膜与SOI纳米线集成，该方法可精确控制薄膜厚度。通过在SOI纳米线的二氧化硅包层中开窗来控制薄膜的放置位置和镀膜长度。由于SOI纳米线与高度非线性GO薄膜之间存在强烈的模式重叠，混合波导的克尔非线性显著增强。使用皮秒光脉冲进行的详细SPM测量表明，对于涂覆有1 - 3层GO的2.2毫米长薄膜和5 - 20层GO的0.4毫米长薄膜的SOI纳米线，光谱展宽显著增强。通过将实验结果与理论拟合，得到了GO的克尔非线性对层数和脉冲能量的依赖性，揭示了从二维单层到准块状行为的层状GO薄膜有趣的物理见解和趋势。最后，我们表明，通过用GO薄膜涂覆SOI纳米线，SOI纳米线的有效非线性参数增加了16倍，有效非线性品质因数（FOM）增加了约20倍，达到FOM > 5。这些结果揭示了使用层状GO薄膜改善硅光子器件克尔非线性光学性能的巨大潜力。
