[论文解读] BiOBr 2D materials for integrated nonlinear photonics devices

Linnan Jia, Dandan Cui+9 more|arXiv (Cornell University)|Jul 31, 2020

Nonlinear Optical Materials Studies参考文献 84被引用 2

一句话总结

本研究证明，BiOBr纳米薄片在800 nm和1550 nm波长下均表现出强烈的三阶光学非线性，非线性吸收系数β ≈ 10⁻⁷ m/W，克尔系数n² ≈ 10⁻¹⁴ m²/W。克尔非线性在这些波长之间由负变正，且β和n²随薄片厚度减小而增大。将其集成到硅波导中后测得低传播损耗，验证了BiOBr作为高性能非线性集成光子学平台的潜力。

ABSTRACT

As a new group of advanced 2D layered materials, bismuth oxyhalides, i.e., BiOX (X = Cl, Br, I), have recently become of great interest. In this work, we characterize the third-order optical nonlinearities of BiOBr, an important member of the BiOX family. The nonlinear absorption and Kerr nonlinearity of BiOBr nanoflakes at both 800 nm and 1550 nm are characterized via the Z-Scan technique. Experimental results show that BiOBr nanoflakes exhibit a large nonlinear absorption coefficient = \b{eta} = 10-7 m/W as well as a large Kerr coefficient n2 = 10-14 m2/W. We also note that the n2 of BiOBr reverses sign from negative to positive as the wavelength is changed from 800 nm to 1550 nm. We further characterize the thickness-dependent nonlinear optical properties of BiOBr nanoflakes, finding that the magnitudes of \b{eta} and n2 increase with decreasing thickness of the BiOBr nanoflakes. Finally, we integrate BiOBr nanoflakes into silicon integrated waveguides and measure their insertion loss, with the extracted waveguide propagation loss showing good agreement with mode simulations based on ellipsometry measurements. These results confirm the strong potential of BiOBr as a promising nonlinear optical material for high-performance hybrid integrated photonic devices.

研究动机与目标

• 表征BiOBr纳米薄片在集成光子应用中的三阶非线性光学特性。
• 研究BiOBr中非线性吸收和克尔非线性的波长与厚度依赖性。
• 展示BiOBr纳米薄片在硅波导中的集成，并评估其在混合集成器件中的性能。
• 通过与基于椭偏仪测得的折射率和消光系数的模场仿真结果对比，验证其非线性光学响应。

提出的方法

• 采用Z扫描技术测量800 nm和1550 nm波长下的非线性吸收和克尔非线性。
• 利用原子力显微镜（AFM）测量机械剥离所得BiOBr纳米薄片的厚度。
• 采用紫外-可见光谱和光谱椭偏仪测定线性光学性质，包括带隙以及1550 nm波长下的折射率（n ≈ 2.2，k ≈ 0.2）。
• 拉曼光谱用于确认BiOBr纳米薄片的结构质量及声子模式。
• 将BiOBr纳米薄片集成到硅波导上，并测量插入损耗以提取波导传播损耗。
• 采用Lumerical FDTD仿真模拟模场分布，并基于测得的n和k值预测传播损耗。

实验结果

研究问题

• RQ1 BiOBr纳米薄片在800 nm和1550 nm波长下的三阶非线性光学特性为何？
• RQ2 BiOBr的克尔非线性（n²）如何随波长变化，是否表现出符号反转？
• RQ3 BiOBr纳米薄片的非线性吸收系数β和克尔系数n²如何随其厚度变化？
• RQ4 BiOBr-硅混合波导的传播损耗是多少，与仿真值相比如何？

主要发现

• BiOBr纳米薄片在800 nm和1550 nm波长下均表现出非线性吸收系数β ≈ 10⁻⁷ m/W。
• BiOBr的克尔系数n²在两个波长下均达到≈ 10⁻¹⁴ m²/W，表明其具有强烈的光学非线性。
• 克尔系数的符号从800 nm处的负值变为1550 nm处的正值，表明n²具有强烈的波长色散特性。
• β和n²均随BiOBr纳米薄片厚度减小而增大，表明其非线性特性具有厚度依赖性增强效应。
• BiOBr-硅混合波导中测得的波导传播损耗与基于椭偏仪数据的FDTD仿真结果高度一致。
• 仿真所得传播损耗略高于实验值，表明材料本征损耗随厚度增加，可能源于散射和层间效应。