Department of Electrical and Computer Engineering, Department of Bioengineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
Department of Mechanical Engineering and Materials Science, Institute of Materials Science and Engineering, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
Nano Lett. 2017 Dec 13;17(12):7569-7577. doi: 10.1021/acs.nanolett.7b03519. Epub 2017 Nov 7.
Nanoantennas offer the ultimate spatial control over light by concentrating optical energy well below the diffraction limit, whereas their quality factor (Q) is constrained by large radiative and dissipative losses. Dielectric microcavities, on the other hand, are capable of generating a high Q-factor through an extended photon storage time but have a diffraction-limited optical mode volume. Here we bridge the two worlds, by studying an exemplary hybrid system integrating plasmonic gold nanorods acting as nanoantennas with an on-resonance dielectric photonic crystal (PC) slab acting as a low-loss microcavity and, more importantly, by synergistically combining their advantages to produce a much stronger local field enhancement than that of the separate entities. To achieve this synergy between the two polar opposite types of nanophotonic resonant elements, we show that it is crucial to coordinate both the dissipative loss of the nanoantenna and the Q-factor of the low-loss cavity. In comparison to the antenna-cavity coupling approach using a Fabry-Perot resonator, which has proved successful for resonant amplification of the antenna's local field intensity, we theoretically and experimentally show that coupling to a modest-Q PC guided resonance can produce a greater amplification by at least an order of magnitude. The synergistic nanoantenna-microcavity hybrid strategy opens new opportunities for further enhancing nanoscale light-matter interactions to benefit numerous areas such as nonlinear optics, nanolasers, plasmonic hot carrier technology, and surface-enhanced Raman and infrared absorption spectroscopies.
纳米天线通过将光学能量集中在远低于衍射极限的位置，实现了对光的终极空间控制，而其品质因数 (Q) 受到大的辐射和耗散损耗的限制。另一方面，介电微腔能够通过延长光子存储时间产生高 Q 因子，但具有衍射受限的光学模式体积。在这里，我们通过研究一个典型的混合系统来弥合这两个世界，该系统集成了等离子体金纳米棒作为纳米天线，以及与共振介电光子晶体 (PC) 平板作为低损耗微腔，更重要的是，通过协同结合它们的优势，产生比单独实体更强的局域场增强。为了在这两种极性相反的纳米光子共振元件之间实现协同作用，我们表明协调纳米天线的耗散损耗和低损耗腔的 Q 因子至关重要。与使用法布里-珀罗谐振器的天线-腔耦合方法相比，该方法已被证明可成功用于放大天线的局域场强度，我们从理论和实验上表明，与适度 Q 值的 PC 导波共振耦合可以产生至少一个数量级的更大放大。协同纳米天线-微腔混合策略为进一步增强纳米级光物质相互作用开辟了新的机会，有益于许多领域，如非线性光学、纳米激光、等离子体热载流子技术以及表面增强拉曼和红外吸收光谱学。
