Fluctuation-dominated materials for advanced photonics

该项目的主要目的是开发用于新型光子应用的纳米结构材料，在这种材料中，设计良好的无序会导致局部电磁场的巨大波动。在这些结构中，具有最大场的热点的非线性响应将占主导地位，平均而言，样品的非线性响应将强烈增加。这种方法可能会导致一种全新的“波动主导型材料”--用于光子学，但对其他基于波的技术也作必要的修改。对于两个模型系统，金属纳米多孔金纳米颗粒(‘Nanosponges’)和介电纳米结构硅纳米针(‘Nanoggras’)，我们建立了场增强因子和电磁模式限制，接近最先进的自上而下纳米技术所能实现的最佳值，例如，在通过聚焦离子束光刻制造的纳米天线中。实验中制备的单个金纳米粒子的近场扫描光谱和超快光电子显微镜解决了长寿命局域等离子体热点，分辨率低于10 nm，与理论计算符合得很好。目前材料科学和纳米加工与最先进的光学表征方法的成功合作，以及对相关近场光学和固体物理的详细的理论分析和建模，将继续以下列目标为目标：(I)基于对热点形成的更深入的理解，制备具有优化无序的材料，以进一步增强场涨落；(Ii)新的实验，用于研究局部增强的非线性响应的空间和时间分辨，以及后者的进一步增加；(3)混合材料的设计、制造和研究，例如，将具有适当量子光学性质的原子或分子大小的小发射器渗透到纳米微孔中。量子发射器与热点模式的耦合使光学功能远远超过组件的功能。最后，我们计划(Iv)进入完全未知的领域，通过研究我们的涨落主导的材料与强太赫兹场的相互作用，这将调制长寿命、超局域热点的相互作用。应该强调的是，对于不同的系统，如金属纳米棒和介电性硅纳米颗粒，已经证实了“涨落主导材料”的范例。这表明潜在的物理机制将存在于许多具有定制无序的系统中，使SPP 1839成为计划中的研究与合作的理想背景和富有成果的环境。

The main aim of this project is to develop nanostructured materials for novel photonic applications in which a well-designed disorder induces huge fluctuations of local electromagnetic fields. In these structures, the nonlinear response of the ‘hot spots’ with largest fields will dominate and, on average, strongly increase the nonlinear response of the sample. This approach may lead to a whole new class of ‘fluctuation-dominated materials’ -- for photonics, but mutatis mutandis for other wave-based technologies as well. For two model systems, metallic nanoporous gold nanoparticles (‘nanosponges’) and dielectric nanostructured silicon nano-needles (‘nanograss’), we established field-enhancement factors and electromagnetic mode confinements that come close to the best values achievable with state-of-the-art top-down nanotechnology, e.g., in nano antenna produced via focus-ion-beam lithography. Experimental near-field scanning spectroscopy and ultrafast photoemission microscopy of a single gold nanosponge prepared within this project resolved long-lived localized plasmonic hot spots with sub-10 nm resolution in excellent agreement with theoretical calculations. The present successful close cooperation of material science and nanofabrication with, on the one hand most advanced optical characterization methods, and on the other hand a detailed theoretical analysis and modelling of the relevant near-field optics and solid-state physics will be continued with the following goals: (i) nanofabrication of materials with optimized disorder for further enhanced field-fluctuations based on a deeper understanding of hot-spot formation; (ii) new experiments for space- and time-resolved studies of the locally enhanced non-linear response and further increase of the latter; (iii) design, fabrication and investigation of hybrid materials where small, typically atom- or molecule-sized emitters with suitable quantum-optical properties are, e.g., infiltrated into nanosponge pores. The coupling of quantum-emitters to hot-spot modes allows optical functionalities far surpassing those of the constituents. Finally, we plan (iv) to enter completely unchartered territory by the study of the interaction of our fluctuation-dominated materials with strong Terahertz fields which will modulate the interaction of the long-lived, ultra-localized hot spots. It should be emphasized, that the paradigm of ‘fluctuation-dominated materials’ has been confirmed for systems as different as metallic nanosponges and dielectric silicon nanograss. This indicates that the underlying physical mechanisms will be present in many systems with tailored disorder, making the SPP 1839 the ideal context and fruitful environment for the planned research and cooperation.