Coherent Control of Light Propagation and Absorption in Complex Media and Resonators

该奖项支持理论研究和相关的教育和培训，以提高我们控制光与物质相互作用的能力。两个主要目标中的第一个目标是通过改变照明条件或其他外部控制参数来操纵和控制材料吸收光的能力。通常，光的吸收被认为是特定材料的一种固定性质，不能轻易和可逆地改变。然而，如果材料在微观水平上进行适当的结构，则可以使其优先吸收，甚至完全吸收具有特定特性的输入光。这种结构被称为相干完美吸收器或反激光，因为它的行为在某种意义上与激光相反，吸收而不是发射特定频率的光。目前的项目将研究如何预测和控制强光信号的吸收。它还将研究如何设计能完美吸收光线的结构。这些和类似的微结构允许光路由的操作是感兴趣的通信和传感，以及芯片上的光学信息处理。第二个重点是研究如何控制光被不吸收的小粒子散射，比如构成白色油漆的那些粒子。通常，这样的散射介质使光束不可能在不扩散和失去焦点的情况下穿透。现代光学仪器提供了合成特定光束的技术，这些光束可以通过这种介质聚焦，只要有足够的关于介质的输入信息。本项目将扩展这种聚焦在散射/不透明介质中的理论，使光束进入介质后在特定时间聚焦到空间中的特定点。这种新型光学控制方式有望改善生物介质（如活组织）深处区域的光学成像。除了研究之外，博士生还将接受国家光子学计划中确定的现代光学技术关键领域的培训。PI将通过他的科普作品和在不同场所的演讲，向普通观众和大学预科学生传达凝聚态物质和光学科学的重要性。该奖项支持理论研究和相关的教育和培训，以提高我们控制光与物质相互作用的能力。该项目包括两个研究重点：无序介质和光物质相互作用的物理学和共振结构。该研究的潜在应用与应用科学的重要优先事项密切相关，涉及通信、信息处理、材料研究和成像。第一个重点解决了最近由PI引入的相干完全吸收或时间反转激光的概念。如前所述，这种现象仅适用于线性吸收，这限制了通过该机制可以传输和吸收的功率。提出的工作将扩展理论来描述饱和吸收剂，并预测在高输入功率下保持完美吸收所需的特性。我们将开发一个从头算理论，考虑到饱和的非线性效应，以及实现该理论的算法和代码，该理论将适用于任意几何形状和复杂性的吸收系统和谐振器。本文将研究完全吸收和光双稳性的共存以及作为光开关的双稳吸收体的特性。最后，在特殊点（非厄米简并）处的相干完美吸收条件将被确定并证明能够实现本征性共振吸收。第二个研究重点是发展不透明强散射介质中光的相干控制理论，特别是在特定时间将光强烈聚焦到这种介质内部或对面的空间区域。这是通过寻找特殊的脉冲输入状态来实现的，这些脉冲输入状态利用多径干涉来偏置光的扩散并实现相干聚焦。空间中不同点的光强之间的相关性将在实现这种相干控制方面发挥关键作用。这项工作在很大程度上建立在介观电子系统中量子输运的见解之上。这项工作将为控制光在强散射介质中的传播和吸收提供一个基于微观计算和随机矩阵理论的一般理论框架，以实现各种优化目标。除了研究之外，博士生还将接受国家光子学计划中确定的现代光学技术关键领域的培训。PI将通过他的科普作品和在不同场所的演讲，向普通观众和大学预科学生传达凝聚态物质和光学科学的重要性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical research and related education and training towards advancing our ability to control light interacting with matter. The first of two main thrusts aims to manipulate and control the ability of a material to absorb light by varying either illumination conditions or other external control parameters. Normally, the absorption of light is considered as a fixed property of a specific material, which cannot be easily and reversibly changed. However, if the material is appropriately structured at a microscopic level, it can be made to preferentially absorb, or even perfectly absorb input light with specific characteristics. Such a structure is called a Coherent Perfect Absorber or Anti-laser, since it behaves in a certain sense like a laser in reverse, absorbing instead of emitting light of specific frequency. The current project will study how to predict and control the absorption of very strong light signals. It will also study how to design structures that will perfectly absorb light. These and similar microstructures that allow the manipulation of light routing are of interest for communications and sensing, as well as for on-chip optical processing of information.The second thrust will study how to control light when it is scattered by small nonabsorbing particles, such as those that make up white paint. Typically, such scattering media make it impossible for a beam of light to penetrate through without spreading out and losing its focus. Modern optical instruments provide techniques for synthesizing particular beams of light that can be focused through such media, given enough input information about the medium. This project will extend the theory of such focusing in scattering/opaque media so as to focus to a specific point in space at a specific time after the beam has entered the medium. This new type of optical control modality shows promise for improved optical imaging of regions deep within biological media, such as living tissue.In addition to the research, PhD students will be trained in critical areas of modern optical technology, as identified in the national photonics initiative. The PI will communicate the importance of condensed matter and optical science to general audiences and precollege students through his popular science writings and lecturing at diverse venues.TECHNICAL SUMMARYThis award supports theoretical research and related education and training towards advancing our ability to control light interacting with matter. The project comprises two research thrusts on the physics of light-matter interactions in disordered media and resonant structures. Potential applications of the research have great relevance to important priorities in applied science, relating to communications, information processing, materials research and imaging.The first thrust addresses the concept of coherent perfect absorption or time-reversed lasing, introduced recently by the PI. As previously developed, this phenomenon only applies to linear absorption, which limits the power that can be transmitted and absorbed via this mechanism. The proposed work will extend the theory to describe saturable absorbers and to predict the properties required to maintain perfect absorption at high input powers. An ab initio theory will be developed that takes into account nonlinear effects of saturation, along with algorithms and codes to implement the theory that will apply to absorbing systems and resonators of arbitrary geometry and complexity. The coexistence of perfect absorption and optical bistability and the properties of such bistable absorbers as an on-off optical switch will be studied. Finally, the conditions for coherent perfect absorption at an exceptional point (non-hermitian degeneracy) will be determined and shown to enable intrinsically chiral resonant absorption.The second research thrust is to develop a theory of coherent control of light in opaque strong-scattering media, specifically focusing light strongly to a region in space within or at the opposite side of such a medium at a particular time. This is achieved by finding special pulsed input states that exploit multipath interference to bias the diffusion of light and achieve coherent focusing. The correlations between the light intensity at different points in space will play a critical role in enabling such coherent control. This work builds heavily on insights from quantum transport in mesoscopic electronic systems. The work will provide a general theoretical framework based on microscopic calculations and random-matrix theory for controlling the propagation and absorption of light in strong scattering media for a variety of optimization goals. In addition to the research, PhD students will be trained in critical areas of modern optical technology, as identified in the national photonics initiative. The PI will communicate the importance of condensed matter and optical science to general audiences and precollege students through his popular science writings and lecturing at diverse venues.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.