利用飞秒激光研究二维材料黑磷和Bi2TexSe3-x的空间自相位调制

Self - diffraction will be observed as spatial self-phase modulation(SSPM) when a high intensity laser passes through two-dimensional material disperse solution. Nowadays, the mechanisms of SSPM have a variety of explanations: strong laser directly lead to; thermal effects lead to; a wind-chime structure formed by the rotation of the two-dimensional material leads to; microbubbles lead to. 2) The modulation of the spatial dimension is limited to two variables: the radius of the diffraction rings (number of rings) and the vertical imbalance; The modulation of the time dimension is not perfect. 3) applications based on the unique properties of two-dimensional materials have not been explored. Applicants have found that the two-dimensional material black phosphorus has strong light sensitivity and ultrafast relaxation time. Two-dimensional topological insulator materials such as Bi2TexSe3-x, have the regular shapes of the hexagonal or round, whose absorption peak wavelength could be controlled by doping. These are the plans to use a wide-band femtosecond laser to study the dynamic SSPM changes of these two two-dimensional materials in solution and gel. The main mechanism will be confirmed. The SSPM on the three dimensions of time, depth and horizontal imbalance will be realized. Also, the unique SSPM application will be given based on the unique properties of two-dimensional materials. The development of this project will fully reveal the SSPM dynamic mechanism of two-dimensional materials, greatly expanding the application of two-dimensional materials.

强激光入射二维材料离散体产生自衍射，这种空间自相位调制现象可以用于测量非线性光学参数和光开关应用。目前，自衍射的机理尚不明朗，争论聚焦在是由二维材料的非线性折射率还是由激光的热效应主导；理论的缺失使得相位调制的维度局限于衍射环半径和竖直失衡度两个变量，研究局限于集体效应而不是微观的单体效应；且应用没有基于二维材料的独特性质。申请人发现黑磷具有强光敏感性和超快弛豫时间；二维拓扑绝缘体Bi2TexSe3-x，为规则形状的六边形或圆形纳米片，能通过掺杂控制吸收峰波长。申请人计划使用宽波段飞秒激光研究这两种二维材料在溶液和凝胶中的动态自衍射变化，确认自衍射机理，实现时间、纵深方向等多个维度上的调制，将研究扩展到微区，给出如超快光开关等二维材料特有的应用。该课题的开展，将全面揭示二维材料自衍射动力学机理，极大扩展其在空间自相位调制领域的应用范围。

本工作通过研究黑磷(BP)、Bi2TexSe3-x、Mxene等新型二维（2D）材料的非线性光学（NLO）特性，探索了超快飞秒激光与微纳材料相互作用的空间自相位调制（SSPM）机制，解决了SSPM的主导机制的判据和模型问题。主要从以下三个方面进行研究：1）物理机制的证明：以Bi2TeSe2材料为研究对象，证明在2D材料的SSPM现象中同时存在着多种物理机制；采用低频超快飞秒激光脉冲，选择合适的波长，可以实现由2D材料原子和分子内电子云的畸变（次皮秒响应）或极性分子取向相关（皮秒响应）主导的SSPM。2）模型改进：以MoS2纳米片离散体为研究对象，验证了规则排列结构的增强效应，在考虑了光强、浓度、与激光作用几率和作用距离的基础上，提出了广义“风铃”模型，解决了高激光光强或高样品浓度时SSPM的饱和现象；并利用BP的液晶现象，定量测量了光控2D材料的规则排列程度。3)材料方面：表征系列新型材料，如Mxene、Bi2Se3、BiOI纳米片等的非线性光学特性，构建复合材料并调制其NLO特性，可研发基于非线性吸收、SSPM效应等的新型全光器件。该系列成果有助于进一步深入研究超快激光脉冲对非线性材料在微纳尺度下的相位调制机制。