Infrared Photorefractive and Light-Emitting Polymers for Optical Technologies

目标。我们提出了一个实验-理论的努力集中在两类多功能有机材料的发展，用于信息技术。第一类材料由红外兼容光折变聚合物组成，适用于可重构滤波器、开关和互连。第二类材料是具有红外发射的π共轭聚合物。这项工作将利用我们过去在开发光折射率和发光聚合物方面的经验，通过结合这些材料上的电子-电子相互作用的多体计算以及它们的电学和非线性光学性质的表征。现有的光折变和发光聚合物的操作仅限于光谱的可见区域，这阻碍了它们在电信中的应用。为了将光折变聚合物的光谱灵敏度扩展到红外，我们将在pi共轭聚合物基体或电活性发色团掺杂剂中使用多光子吸收从高能量双光子激发态产生光电性。理论工作将在确定双光子态中进行，从而提高光发生效率。这些结果也将指导响应时间为亚毫秒的单光子光折变聚合物的设计。寻找具有红外光致发光的pi共轭聚合物将建立在我们最近发现的原理之上，即在具有大分子单位细胞的pi共轭聚合物中获得有利于低频光发射的激发态有序。具体的结构要求是在聚合物链上存在与共轭方向横向的分子共轭，导致光激子的纵向约束和横向离域。对满足红外发射结构要求的聚异噻吩可溶性衍生物进行实验研究。意义和影响。所提出的红外兼容光折变和发光聚合物将使电信技术的新设备成为可能。尽管有机光电子学领域取得了快速进展，但现有的器件中的有机材料主要在电磁波谱的可见区域工作。我们的工作将扩展光谱的应用范围，预计我们的研究成果将对有机材料的器件物理产生强烈的影响。其目的不是与利用传统无机半导体的技术竞争，而是利用有机材料独特的加工能力开发新的功能和应用。重要的是，实验和理论之间的强耦合将导致加强对有机物质中光产生，多光子吸收和光发射的基本过程的理解，这一领域仍处于起步阶段。最后，本研究提供了一个独特的多学科框架来整合研究与教学。参与该项目的学生将接触到化学、光学、工程以及非线性吸收、电荷注入、电荷和能量转移以及光发射等基础物理。

Objectives. We propose an experiment - theory effort focused on the development of two classes of multifunctional organic materials to be used for information technologies. The first class of ma-terials consist of infrared compatible photorefractive polymers that are suitable for reconfigurable filters, switches and interconnects. The second class of materials are pi-conjugated polymers with emission in the infrared. This effort will capitalize on our past experience in developing photorefrac-tive and light emitting polymers through a combination of many-body calculations incorporating electron-electron interactions on these materials and the characterizations of their electrical and nonlinear optical properties. The operation of existing photorefractive and light emitting polymers is restricted to the visible region of the spectrum which prevents their use in telecommunication.Approach. To extend the spectral sensitivity of photorefractive polymers to the infrared we will use multiphoton absorption to generate photoconductivity from high energy two-photon excited states in either a pi-conjugated polymer matrix or an electro-active chromophore dopant. Theo-retical work will be performed in identifying two-photon states from which enhanced photogener-ation efficiency is expected. These results will also guide the design of one-photon photorefractive polymers with sub-millisecond response time. The search for pi-conjugated polymers with photo-luminescence in the infrared will build on our recent discovery of the principle that excited state ordering conducive to light emission at low frequencies is obtained in pi-conjugated polymers with large molecular unit cells. The specific structural requirement is that there exists molecular conju-gation transverse to the direction of conjugation along the polymer chain, leading to longitudinal confinement and transverse delocalization of the optical exciton. Experimental studies will be con-ducted on soluble derivatives of poly(isothianaphthene), which satisfy the structural requirement for infrared emission.Significance and Impact. The proposed infrared compatible photorefractive and light emitting polymers will enable new devices for telecommunication technologies. In spite of the rapid advances made in the area of organic optoelectronics, existing organic materials amid devices operate largely in the visible region of the electromagnetic spectrum. Our work will extend the spectral range of applications, and it is expected that the outcomes of our research will have strong impact on the device physics of organic materials. The aim is not to compete with the technology utilizing con-ventional inorganic semiconductors, but to develop new functionalities and applications, utilizing the unique processing capability of organic materials. Importantly, the strong coupling between experiment and theory will lead to enhanced understanding of the fundamental processes of photo-generation, multiphoton absorption and light emission in organics, an area that is still in its infancy. Finally, the proposed research provides a unique multidisciplinary framework to integrate research and teaching. Students working on the project are exposed to chemistry, optics, engineering, and the fundamental physics of nonlinear absorption, charge-injection, charge- and energy-transfer, and light emission.