Magnetic-Free, Non-Reciprocal Integrated Nanophotonic Components Based on Angular-Momentum Bias

基于角动量偏置光隔离器的无磁、非互易纳米光子器件，允许光子在一个方向上传播但禁止反向传播的装置对于在光纤网络中路由光信号和提供激光器操作的稳定性起着至关重要的作用。目前市场上的隔离器都是基于磁偏置石榴石或铁磁材料。然而，由于磁光效应的弱特性，它们通常基于庞大的光学部件，它们基于昂贵的材料，并且由于与常规衬底的晶格失配，它们不可能集成在纳米光子平台中。这项工作的目标包括引入新的理论概念和设计原则，以及实验实现集成的纳米光子器件，可以隔离，而不需要磁效应。我们的方法是集中在纳米光子模拟的塞曼效应，物理机制的基础上，传统的隔离实现与磁性材料：我们将能够诱导一个强大的隔离片上偏置角动量适当设计的“元原子”的形式时空调制纳米环谐振器。该项目的研究结果预计将吸引纳米光子学行业的极大兴趣，因为非互易纳米器件的单片集成可以显着降低这些基本器件的成本和占地面积。更广泛地说，拟议的研究结合了电气工程中大量令人兴奋的主题，可以直接涉及电气工程中一些最重要领域的本科生和研究生，如纳米光子学，超材料，集成电子学，纳米纤维和建模，为激励下一代科学家和研究人员提供独特的机会。拟议的研究为纳米光子学引入了颠覆性概念，允许实现无磁光学组件，该组件可以打破洛伦兹互易性，而无需磁偏置或特殊的铁磁响应。完全基于传统纳米光子板中已经可用的组件和材料，例如介电波导和半导体结，新提出的非互易组件可以直接集成到传统的纳米光子系统中。此外，所提出的结构将最佳地受益于硅光子学、纳米光学和电子学等快速发展领域的最新进展。在完成这项工作时，我们将展示基于角动量偏置的非互易光学组件，该组件是通过基于电射频信号的共振纳米环的适当时空调制实现的。在方位角方向上的强共振和精确形式的时空调制的仔细组合将能够大幅增强负责时空调制的原本弱的电光效应，从而导致在与波长相当或小于波长的覆盖区内的巨大非互易性。我们对等离子体和石墨烯平台中的角时空调制的额外研究将为一种新的技术平台奠定基础，该平台能够以新的方式在深亚波长尺度上处理和控制光。

Magnetic-Free, Non-Reciprocal Nanophotonic Components Based on Angular-Momentum BiasOptical isolator i.e., devices that allow photons to travel in one direction, but prohibit reverse propagation play a crucial role to route optical signals in optical fiber networks and to provide stability in laser operation. Commercially available isolators today are exclusively based on magnetically-biased garnets or ferromagnetic materials. However, because of the weak character of magneto-optical effects, they are typically based on bulky optical components, they are based on expensive materials, and they are impossible to integrate in a nanophotonic platform due to lattice mismatch with conventional substrates. The objective of this effort consists in introducing new theoretical concepts and design principles, as well as experimentally realizing integrated nanophotonic devices that can isolate without requiring magnetic effects. Our approach is centered on the nanophotonic analog to the Zeeman effect, the physical mechanism based on which conventional isolation is realized with magnetic materials: we will be able to induce a strong isolation on-chip by biasing with angular-momentum suitably designed "meta-atoms" in the form of spatio-temporally modulated nanoring resonators. The findings of this project are expected to attract significant interest from the nanophotonics industry, since monolithic integration of non-reciprocal nanodevices can dramatically minimize the cost and footprint of these essential devices. More broadly, the proposed research combines a plethora of exciting topics in electrical engineering, that can directly involve undergraduate and graduate students in some of the most important fields of electrical engineering such as nanophotonics, metamaterials, integrated electronics, nanofabrication, and modeling, opening unique opportunities to inspire the next generation of scientists and researchers, with special attention to under-represented minorities.The proposed research introduces disruptive concepts for nanophotonics, allowing the realization of magnetic-free optical components that can break Lorentz reciprocity without requiring magnetic bias or special ferromagnetic response. Being fully based on components and materials that are already available in conventional nanophotonic boards, such as dielectric waveguides and semiconductor junctions, the newly proposed non-reciprocal components can be directly integrated into conventional nanophotonic systems. In addition, the proposed structures will optimally benefit from recent advances in the quickly growing fields of silicon photonics, nano-optics and electronics. At completion of this effort, we will have demonstrated non-reciprocal optical components based on angular-momentum biasing, achieved with suitable spatio-temporal modulation of resonant nanorings based on electric radio-frequency signals. The careful combination of a strong resonance and of a precise form of spatiotemporal modulation in the azimuthal direction will be able to drastically enhance the otherwise weak electro-optical effects responsible for spatio-temporal modulation, thus leading to giant non-reciprocity within a footprint comparable or smaller than the wavelength. Our additional investigations of angular spatio-temporal modulation in plasmonics and graphene-based platforms will set the basis for a new technology platform able to process and control light in novel ways at a deeply subwavelength scale.