Towards an Infrared Nanophotonic Nose: Ultracompact Spectroscopic Photodetection based on Plasmonic Nanoantenna-diodes

识别大气、供水和呼出的呼吸或体液中的小分子是一项极其重要的能力，其应用范围从识别危险的环境毒素到早期疾病检测。然而，目前可用于进行这类化学鉴定的方法需要大型、昂贵和灵敏的仪器，仅在实验室环境中可用，并且基于数十年的技术。这项研究资助的工作旨在结合两个最新的研究进展，开发一种识别小分子的新方法。这项工作最终可能提供超致密几何结构的化学识别能力，可用于各种非实验室环境。快速检测和准确识别临床或现场分子的能力在农业、制药、食品质量控制和包括大脑功能在内的医学筛查等领域有着广泛的应用。这种方法最终可以用于在完全集成的、基于芯片的检测水平上识别多个分子，最终与基于云的处理和基于智能手机的数据采集兼容。这项提议的核心是交叉的、多学科的概念，为高中、本科生和研究生水平的学生教育提供了广阔的机会。技术描述：这项提议的目标是开发基于窄带纳米天线二极管的高度紧凑的红外光谱能力，用于近红外分子光谱。最近在纳米光子学方面取得了两项独立的研究进展，它们结合在一起，非常适合实现这一目标。它们是：(1)光学活性纳米天线-二极管的演示，其中载流子是由共振金属纳米天线中的光激发表面等离子体衰变产生的，然后被注入到邻近半导体的导带中；(2)红外纳米天线的发展调谐到特定化学官能团的共振振动频率。通过将这两个概念融合在一起，将创造出窄带、红外有源纳米天线二极管，用于通过直接电读数进行小分子的光谱识别。工作将侧重于开发具有更高响应度和量子效率的纳米天线二极管，通过实施增益和线型控制纳米天线-二极管光谱响应，以最终分辨光谱近红外区域的分子谱线。这种方法最终将消除对基于昂贵材料的近红外光电探测器的需求，以及传统红外光谱用于波长识别所需的笨重的色散光学元件和较大的光路长度。

The identification of small molecules in our atmosphere, water supply, and exhaled breath or body fluids, is an extremely important capability with applications ranging from identification of dangerous environmental toxins to early-stage disease detection. The methods that are currently available to perform this type of chemical identification, however, require large, expensive and sensitive instruments, are available only in laboratory settings, and are based on decades-old technologies. The work enabled by this research grant aims to combine two recent research advances to develop a new approach for identifying small molecules. This work could ultimately provide chemical identification capabilities in ultracompact geometries that could be used in a variety of non-laboratory settings. The ability to rapidly detect and accurately identify molecules in the clinic or in the field has wide-ranging has applications in areas ranging from agriculture, pharmaceuticals, food quality control, and medical screening, including brain function. This approach could ultimately be used for identifying a plurality of molecules at a fully integrated, chip-based level of detection compatible, ultimately, with cloud-based processing and smart-phone-based data acquisition. The cross-cutting, multidisciplinary concepts central to this proposal provide a broad opportunity for student education at the high school, undergraduate, and graduate student level. Technical Description: The goal of this proposal is to develop highly compact infrared spectroscopic capabilities based on narrowband nanoantenna-diodes for near-infrared molecular spectroscopy. Two independent research advances in nanophotonics were recently pioneered which, when combined, are ideally suited to address this goal. They are: (1) the demonstration of optically active nanoantenna-diodes, where carriers are generated by the decay of photoexcited surface plasmons in resonant metallic nanoantennas, then injected into the conduction band of the adjacent semiconductor, and (2) the development of infrared nanoantennas tuned to the resonant vibration frequencies of specific chemical functional groups. By merging these two concepts, narrowband, infrared active nanoantenna-diodes for the spectroscopic identification of small molecules with direct electrical readout will be created. Efforts will focus on the development of nanoantenna-diodes with enhanced responsivities and quantum efficiencies, through the implementation of gain, and on lineshape control of the nanoantenna-diode spectral response, to ultimately resolve molecular spectral lines in the near-infrared region of the spectrum. This approach would ultimately eliminate the need for near-infrared photodetectors based on costly materials, along with the bulky dispersive optics and large optical path lengths required in conventional infrared spectroscopy for wavelength discrimination.