CAREER: Dynamic nanophotonic spectral and directional control of thermal emission

热辐射，即所有物体发出的电磁波，是我们这个世界普遍存在的特征。控制热辐射的发射和吸收对于一系列能源技术及其所依赖的热源至关重要。除了能源技术，从传感到成像和黑暗环境下的检测，热源也是我们感知周围世界的基础技术。该项目旨在实现对热辐射的频谱和方向性的动态调谐。这项研究将阐明新的机制，利用纳米光子设计和红外波长上独特的材料特性相结合来调节热源的热流。这些发现将使新的，更紧凑的红外成像和传感源和探测器，以及改进的材料平台，以控制能量和传热应用的热流。主要研究目标与教育和推广活动紧密结合，这些活动旨在通过在线视频和更新的课程吸引高中到研究生阶段的学生，并积极吸引热脆弱社区的社区成员。这些活动将通过确定所需的关键技术能力以及研究成果的新应用机会来反馈核心研究目标。传统材料和器件的热发射通常是广谱的，各向同性和静态的，发射光谱和强度受发射器的温度控制。由于这些特性，动态控制热源的发射率的光谱和方向特性是一项具有挑战性的任务，但对于红外成像和传感以及热传递和能量应用具有根本重要性。当今的典型方法涉及使用体光学元件，包括光谱滤波器沿着机械移动来移动或重新定向源，并改变其光谱特性以满足目标功能。虽然最近已经取得了进展，使用光子和超材料的策略来改变发射率特性，动态控制发射的热辐射的光谱和方向性仍然是一个开放的挑战。该项目将展示梯度折射率近零的热纳米光子设备，可以动态调整其光谱和方向发射率超过长波红外波长。PI将表征渐变掺杂的半导体薄膜，并表征其在红外波长上的光学特性。然后，这些薄膜将被配置成结结构，以动态地调整大带宽上的光谱和定向发射，并实现对发射率的强电气控制。最后，该项目还将展示可以动态调整发射热辐射的光谱、方向和偏振特征的元表面。该奖项反映了NSF的法定使命，并且通过使用基金会的知识价值和更广泛的影响进行评估，被认为值得支持审查标准。

Thermal emission, the electromagnetic waves emitted by all objects, is a ubiquitous feature of our world. Controlling emitted and absorbed thermal radiation is of paramount importance for a range of energy technologies and the sources of heat they rely on. Beyond energy technologies, from sensing to imaging and detection in dark environments, thermal sources serve also serve as a foundational technology for our ability to perceive the world around us. This project seeks to enable the dynamic tuning of both the spectrum and directionality of thermal emission. The research will illuminate new mechanisms to tune heat flows from sources using a combination of nanophotonic design and unique material properties over infrared wavelengths. These findings will enable new, more compact sources and detectors for infrared imaging and sensing, as well as improved materials platform to control heat flows for energy and heat transfer applications. The key research aims are closely integrated with education and outreach activities that seek to engage students from the high-school through graduate level through online videos and updated courses, as well as actively engaging community members in heat-vulnerable communities. These activities will feed back into the core research aims by identifying key technical capabilities needed as well as opportunities for new applications of the research findings.Thermal emission from conventional materials and devices is typically broad spectrum, isotropic and static in nature, with the emitted spectrum and intensity controlled by the emitter’s temperature. Due to these characteristics, dynamically controlling the spectral and directional characteristics of the emissivity of a thermal source is a challenging task, but of fundamental importance for infrared imaging and sensing, as well as heat transfer and energy applications. Typical approaches today involve using bulk optical elements, including spectral filters along with mechanical movement to move or re-orient a source, and alter its spectral characteristics to meet a target functionality. While recent progress has been made using photonic and metamaterials strategies to alter emissivity characteristics, dynamic control of both the spectrum and directionality of emitted thermal radiation remains an open challenge. This project will demonstrate gradient epsilon near zero-based thermal nanophotonic devices that can dynamically tune both their spectral and directional emissivity over long-wave infrared wavelengths. The PI will characterize graded doped semiconductor films and characterize their optical properties over infrared wavelengths. These films will then be configured into junction architectures to dynamically tune spectral and directional emission over large bandwidths and achieve strong electrical control of emissivity. Finally, the project will also demonstrate metasurfaces that can dynamically tune spectral, directional and polarization characteristics of emitted thermal radiation.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.