黑磷量子点的非线性光学特性研究

As a resurged semiconducting material, black phosphorus(BP) possesses thickness-dependent direct energy band gap that could be widely tunable within a broad region from 0.3 eV (bulk) to 1.5 eV (monolayer), exactly bridging the gap between its two-dimensional counterparts: graphene (zero band gap) and transition metal dichalcogenides (TMDs) (relatively wide band gap: 1.5 eV~2.5 eV), while BP exhibits attractive broadband third-order nonlinear optical responses ranging from the visible to mid-IR and widely used in ultrafast photonics as optical saturable absorber. Additionally, BP has unique anisotropic nature for optoelectronics and electronics, while the other two-dimensional nano-materials are generally isotropic. Consequently, BP shows promise as a nano-material that could complement or exceeds the electronic, nonlinear optical and optoelectronic properties of graphene and TMDs..Ultrasmall BP nanosheets (also called as BP quantum dots, BPQDs) exhibit unique electronic and optical properties in association with the quantum confinement and edge effects, may be developed as another kind of promising nanomaterial for ultrafast photonics..In this project, both the open and closed aperture Z-scan laser measurements will be employed to investigate the nonlinear optical response (saturable absorption and nonlinear refraction) of BPQDs while the pump-probe experiment is carried out to investigate the carrier dynamics. Our work will provide researchers with theoretical and experimental basis of BPQDs, paving the way towards BPQDs based electronics and optoelectronics applications.

黑磷量子点是一种新型的黑磷材料，由于具有量子限定效应和边界效应，已被证实具有比黑磷纳米片材料更优异的光学性能，在超快光子学的应用具有巨大的潜力，有望发展成为一种新型的光学功能材料。受限于黑磷量子点易氧化的特性，以及黑磷与光相互作用的机理的未知，黑磷量子点在超快光子学中的应用还尚属于探索阶段。.本项目拟制备抗氧化的黑磷量子点薄膜，采用可调谐的超短脉冲激光、Z扫描和泵浦探测等方法，从实验上系统研究黑磷量子点材料的宽带非线性效应和带内驰豫时间，从理论上揭示黑磷量子点材料在可见光到中红外波段的非线性光学规律和光激发载流子动力学规律，探索出黑磷量子点材料与光的作用机理，为黑磷量子点材料在激光技术等方面的应用奠定理论和实验基础，为黑磷量子点走出实验室，迈向实际应用解决技术难点。

黑磷量子点是一种新型的黑磷材料，具有量子限定效应和边界效应，已被证实具有比黑磷纳米片材料更优异的光学性能，在超快光子学的应用具有巨大的潜力，有望发展成为一种新型的光学功能材料。本项目研究了（1）黑磷材料的尺寸对其非线性光学特性的影响。通过Z 扫描方法和泵浦-探测技术从实验上证实，黑磷材料的横向尺寸越小，它的三阶非线性系数越大，调制深度越大，可饱和光强越小，响应时间越短。也就说，尺寸越小的黑磷材料，具有更好的非线性光学性能，从而进一步证实了黑磷量子点具有优异的非线性光学性能。（2）解决了黑磷量子点在潮湿环境下容易氧化的问题。采用静电纺丝技术，将黑磷量子点纺在聚甲基丙烯酸甲酯纳米纤维薄膜中，形成透明均匀的复合纳米纤维薄膜。实验发现这种复合纳米纤维薄膜完整地保存了黑磷量子点的化学性质和非线性光学性质。由于这种复合纳米纤维薄膜易制备、抗氧化和均匀透明等优点，将推动黑磷量子点在光电器件中的广泛应用。（3）进一步寻找研究其他可以制作光电器件的候选二维材料。用旋涂法制备了二硫化钛薄膜，用Z 扫描方法研究了二硫化钛薄膜的非线性光学特性。实验结果表明，二硫化钛薄膜在入射波长为400 nm、800 nm、1560 nm和1930 nm都展现了宽波段非线性光学特性，特别是在通信波段，可以作为超快光电子器件在通信波段的候选材料。该项研究为寻找合适的光电子器件制作材料提供了一种解决思路。