Linear and nonlinear optical properties of metallic photonic crystals and pseudo/negative index materials

金属光子晶体可以由金属纳米粒子在波导上的规则阵列组成。光的强耦合，特别是通过这个底层的波导，导致集体状态。这些态由局域粒子等离激子和扩展的极化激子组成，类似于半导体微腔中的腔极化子。我们在这个项目中有两个目标：(A)我们想要了解和描述光-粒子-等离子激元耦合系统的线性光学性质，特别是与单个金属纳米粒子光谱有很大不同的光学传输和反射性质。例如，我们发现强Fano共振是窄共振和连续体之间干涉的标志。这些干涉态的性质究竟是什么，它们是如何耦合的？是什么决定了耦合强度？这些耦合系统是否形成了一个完整的光子带隙？是什么决定了简正模耦合的大小？(B)耦合系统表现出一种新的激发类型，即所谓的粒子-等离子体激元-波导-极化子。这些激发的寿命是多少，它们的退相时间是多少？我们想要用非线性飞秒光谱，例如自相关光谱来研究这些相干性质。是否有可能调整耦合系统的退相时间？我们能量化辐射和非辐射对退相率的贡献吗？迎接这些挑战将使人们对金属光子晶体中集体激发的线性和非线性光学性质有一个更基本和更全面的了解。

Metallic photonic crystals can be composed of regular arrays of metallic nanoparticles on a waveguide. Strong coupling by light, especially through this underlying waveguide, leads to collective states. These states consist of localized particle plasmons and extended polaritonic excitations, similar to cavity polaritons in a semiconductor microcavity. We have two goals in our project: (a) We would like to understand and describe the linear optical properties of the coupled light-particle-plasmon system, especially the optical transmission and reflection properties that differ substantially from the spectra of individual metal nanoparticles. For example, we found strong Fano resonances as a sign of interference between a narrow resonance and a continuum. What exactly is the nature of these interfering states, and how are they coupled? What determines the coupling strength? Do these coupled systems form a complete photonic bandgap? What determines the size of the normal-mode coupling? (b) The coupled system exhibits a new type of excitations, so-called particle-plasmon-waveguide-polaritons. What is the lifetime of these excitations, what is their dephasing time? We want to study these coherent properties using nonlinear femtosecond spectroscopy, e.g., autocorrelation spectroscopy. Is it possible to tailor the dephasing times of the coupled system? Can we quantify the radiative and nonradiative contributions to the dephasing rate? Meeting these challenges will yield a fundamental and more complete understanding of the linear and nonlinear optical properties of collective excitations in metallic photonic crystals.