Exploring the Frontier of Photonic Device Size, Speed, and Efficiency Limits with Gain-enhanced Multifuncional Metamaterials

摘要：（非技术）金属介电复合材料作为下一代信息、通信和传感系统的基石具有重要的前景。金属和介电材料的结合提供了前所未有的小体积，快速度，并增强了光子器件（如光源，波导和开关）的非线性效应。然而，一般来说，金属的掺入必然会增加在这种装置中作为热量散失的能量，从而减少有用信号所携带的能量。我们建议创建金属-介电和金属-半导体复合材料，其主要目标是展示无能量损失的光信号传输。半导体材料可以被设计成在很宽的颜色范围内发射和吸收光，它们的特性可以通过外部电子设备来调节。我们的目标是发展有源半导体在实现光信号传播而不损失能量方面的作用的理论基础和实验知识，同时仍然保持基于金属介电的光子器件的小占地和快速运行。此外，我们计划从理论上和实验上探索由于电磁场的局部增强和组成材料之间的界面上存在的级联非线性而增强的非线性效应。（技术）与传统光学材料相比，双曲超材料提供了独特和增强的功能。例如，双曲型超材料在深度亚波长体积中表现出高度局域化的电场，从而实现了场增强的非线性极化，以及自发发射率的宽带Purcell增强。通过引入外部应变，可以进一步修改组成材料的能带结构，从而实现双曲型超材料线性和非线性光学响应的多尺度工程。不幸的是，双曲型超材料通常遭受相当大的欧姆损耗，阻碍了它们在实际设备中的适用性。为了克服这一缺陷，可以引入光增益来改善器件性能。迄今为止，大多数关于增益补偿超材料的研究都集中在染料分子作为增益介质上，因为它们易于纳入概念验证实验，并且可以使用简单的两级系统精确建模。相比之下，无机半导体及其异质结构作为增益介质是有吸引力的，因为它们的吸收/发射共振可以从太赫兹到紫外线频率进行设计。此外，半导体双曲型超材料可以通过电注入电荷载流子，从而可以更直接、更可靠地控制其功能。最后，无机半导体在稳健性、寿命和与导波器件的可积性方面比染料具有明显的优势。本提案的总体目标是推进增益增强多功能超材料的科学和技术。具体来说，我们的目标是全面理解和实验证明：(1)基于波导的增益增强多功能超材料中的无损传播，(2)增益增强多功能超材料中的场增强二阶和三阶非线性效应，以及(3)增益增强多功能超材料中的应变增强非线性效应，这些效应都是由半导体增益介导的。为了特异性，我们专注于光谱的近红外部分，但我们强调，从我们的工作中吸取的经验教训可以很容易地扩展到紫外线和太赫兹频率。增益增强多功能超材料为实现前所未有的非线性转换效率和无损信号传输提供了途径。由于其极小的占地面积和潜在的快速操作，增益增强多功能超材料将成为未来光子电路集成非线性器件的有力候选者。提出的研究不仅将推进有源半导体超材料的基础科学和技术，而且还将为研究电子，电磁和机械相互作用的自一致处理变得至关重要的物理现象树立榜样。我们预计增益增强多功能超材料将在数据和电信、图形处理、计算、生物医学成像和化学传感等领域得到应用。

Abstract title: Exploring the Frontier of Photonic Device Size, Speed, and Efficiency Limits with Gain-enhanced Multifuncional Metamaterials Abstract: (Non-technical)Metal-dielectric composites hold significant promise as the building blocks of next-generation information, communication, and sensing systems. The combination of metals and dielectrics offers unprecedentedly small volumes, fast speeds, and enhancements to nonlinear effects in photonic devices such as light sources, waveguides, and switches. Generally, however, the incorporation of metals necessarily increases the energy dissipated as heat in such devices, consequently reducing the energy carried by useful signals. We propose to create metal-dielectric and metal-semiconductor composites with the primary goal of demonstrating optical signal transmission without energy loss. Semiconducting materials may be engineered to emit and absorb light over a very broad color range, and their properties may be tuned by external electronics. We aim to develop the theoretical underpinning and experimental knowledge on the role of active semiconductors in enabling propagation of optical signals without loss of energy, while still retaining the small footprint and fast operation of the metal-dielectric-based photonic devices. We additionally plan to explore, both theoretically and experimentally, the enhancement of nonlinear effects in such devices, due both to the local enhancement of electromagnetic fields and to the cascaded nonlinearities present at the interfaces between the constituent materials. (Technical) Hyperbolic metamaterials offer unique and enhanced functionalities compared to conventional optical materials. For example, hyperbolic metamaterials exhibit highly localized electric fields in deeply subwavelength volumes, enabling field-enhanced nonlinear polarization, as well as broadband Purcell enhancement of the spontaneous emission rate. By introducing external strain, the band-structure of the constituent materials can be further modified, enabling multi-scale engineering of the hyperbolic metamaterials's linear and nonlinear optical responses. Unfortunately, hyperbolic metamaterials typically suffer from considerable Ohmic losses, preventing their applicability to practical devices. To overcome this deficiency, optical gain may be introduced for improved device performance. To date, most research on gain-compensated metamaterials has focused on dye molecules as a gain medium because they are easy to incorporate in proof-of-concept experiments and can be accurately modeled using simple two-level systems. In contrast, inorganic semiconductors and their heterostructures are attractive as gain media because their absorption/emission resonances may be engineered from terahertz to ultraviolet frequencies. Additionally, semiconductor hyperbolic metamaterials may be electrically injected with charge carriers, allowing for a more direct and reliable control of their functionality. And lastly, inorganic semiconductors offer distinct advantages over dyes in terms of robustness, lifetime, and integrability with guided wave devices. The overall goal of this proposal is to advance the science and technology of Gain Enhanced Multifunctional Metamaterials. Specifically, we aim to comprehensively understand and experimentally demonstrate: (1) lossless propagation in waveguide-based Gain Enhanced Multifunctional Metamaterials, (2) field-enhanced second- and third-order nonlinear effects in Gain Enhanced Multifunctional Metamaterials, and (3) strain-enhanced nonlinear effects in Gain Enhanced Multifunctional Metamaterials, all mediated by semiconductor gain. For specificity, we focus on the near-infrared part of the spectrum, but we stress that the lessons learned from our work may easily be extended to ultraviolet and terahertz frequencies alike. Gain Enhanced Multifunctional Metamaterials offer an avenue for achieving unprecedented nonlinear conversion efficiencies with lossless signal transmission. Due to their extremely small footprint and potentially fast operation, Gain Enhanced Multifunctional Metamaterials will become strong candidates for integrated nonlinear devices of future photonic circuits. The proposed research will not only advance the basic science and technology of active semiconductor metamaterials, but will also set an example for the investigation of physical phenomena in which the self-consistent treatment of electronic, electromagnetic, and mechanical interaction becomes crucially important. We anticipate that Gain Enhanced Multifunctional Metamaterials will find applications in data- and telecommunications, graph-processing, computation, biomedical imaging, and chemical sensing.