基于功能分子取向组装的双光子微腔激光材料

Microcavity lasers are the essential components of optoelectronic integrated chips，while two-photon pumped lasing provides a flexible method to extend working wavelength regime broadly based on frequency upconversion process. For two-photon pumped microcavity laser, the reduced gain length and nonlinear optical feature require excellent laser gain media with much higher gain coefficients than conventional laser. This project aims to develop a kind of novel host-guest laser media that are comprised of porous crystals, metal-organic frameworks (MOFs), and aligned luminescent building blocks. We propose a functional optimization strategy to improve the gain coefficients at a specific working direction, as well as generate linearly polarized lasing, by enhancing the order of alignment structure. Two alignment methods, both governed by the static interaction between host and guest components and dynamically induced by laser electric field, are suggested to improve the order of functional blocks in the host-guest systems. The polarized absorption, luminescence spectra technique in microscopic scale will be established to evaluate the static and dynamic orientation of functional guest species, with the help of time-resolved spectra, which will facilitate the clarification of the rules controlling over the alignment of guest species in such a system with multiple interactions between host MOFs and guests. It is envisaged that the results of this research proposal will pave the way for demanded two-photon pumped laser materials and microcavity laser with high efficiency, low threshold, single mode and linear polarization.

微腔激光器是光电子集成芯片的关键元件，双光子激光通过频率上转换可以极大地拓展工作波段，而双光子微腔激光器超短的增益长度和非线性光学特性对激光材料的增益性能提出了更高的要求。本项目拟以多孔晶态材料—离子型金属-有机框架（metal-organic frameworks，MOFs）材料作为载体，发展基于离子型发光染料取向组装的主-客体激光介质，提出“通过功能基元取向结构的优化，提高材料特定工作方向的增益系数，并实现激光线偏振输出”的功能优化策略。发展主、客体间静态相互作用控制的以及光电场动态诱导的取向结构的优化方法，综合运用微区偏振吸收、发光光谱与时间分辨光谱技术，建立固态材料中客体离子静态和动态取向结构的表征手段，探索多作用体系中主、客体因素对客体分子取向和材料性能的影响规律，为实现高效率、低阈值、单纵模、线偏振输出的双光子微腔激光提供材料构筑思想、性能优化途径和基础理论依据。

微腔激光器是光电子集成芯片的关键元件，多光子激光通过频率上转换可以便捷地拓展工作波段，而多光子微腔激光器超短的增益长度和非线性光学特性对激光材料的增益性能提出了更高的要求。本项目采用多孔晶态材料—离子型金属-有机框架（metal-organic frameworks，MOFs）材料作为载体，发展了基于离子型发光染料取向组装的主-客体激光介质，实施了“通过功能基元取向结构的优化，提高材料特定工作方向的增益性能，并实现激光线偏振输出”的功能优化策略。主要研究内容为：1）新型金属-有机框架材料的合成与微晶尺寸调控的探索；2）显微偏振吸收、荧光光谱测试系统的搭建，用于局域取向结构的表征；3）客体在晶体孔道中的取向程度的影响规律和取向结构的实现方法；4）染料/金属-有机框架材料及其多（双、三）光子激射性能。. 获得了一种具有一维狭窄通道（宽度约为6 Å）的离子型金属-有机框架材料ZJU-68。晶体外形呈现规则的六方柱状，在水、空气和激光下具有良好的稳定性，尺寸在几百纳米到几百微米范围内可调，可形成Fabry-Perot腔和耳语围廊腔。ZJU-68的孔道尺寸正与有机激光染料离子DMASM相近，可通过原位组装将染料离子引入框架。框架孔道内的DMASM分子形态能够通过电子密度成像的方式清楚地呈现，呈现高度的取向结构。得益于ZJU-68狭窄孔道对分子运动的限域效应，染料/金属-有机框架材料的量子效率从溶液状态的0.45%大幅提高到24.28%。高浓度、均匀，高度取向的染料装载，同时利用框架材料单晶的天然晶面作为谐振腔的反射镜面，不仅在MOFs单晶中首次实现了12.6 pJ（单光子泵浦）和19.6 nJ（双光子泵浦）的低阈值单模线偏振微腔激光，还成功地在国际上首次实现高偏振度（大于99.9％）的三光子泵浦激光，其品质因子Q值高达1700。. 以上结果为金属-有机框架材料在光子学上的应用提供了新的思路和方法，并将推动其在光子元器件与集成光子芯片上的应用。受项目资助，在Nature Commun.、Adv. Opt. Mater. 和J. Am. Chem. Soc等期刊发表研究论文8篇，授权专利1项。