CAREER: Chip-Scale, Field-Resolved Detection of Mid-Infrared Light

电磁波谱的中红外部分对生物、化学和物理科学具有重要意义。中红外线（MIR）由波长约为百万分之三到二十米的电磁波组成。在这个光谱区，几乎所有的分子都表现出吸收共振，这些共振构成了分子指纹。因此，在过去的一百年里，MIR光已经被用于传感，最近的应用范围从环境监测到蛋白质表征。在过去的几十年里，在超快MIR激光光源方面取得了革命性的进展，即产生MIR光的短脉冲的激光系统。这种超快MIR源为增强MIR传感技术提供了新的、令人兴奋的机会。该项目的第一个目标是开发专门为超快MIR激光源量身定制的新型探测器。这些探测器将使在时域测量MIR激光脉冲的光场成为可能。这种场分辨探测器将使MIR传感具有更高的分辨率，并提供新的能力来研究MIR吸收共振的动态行为。该项目的第二个目标是促进工程教育的工程学生保留率。为此，将为使用超快激光技术的研究生开发在线教育内容；在本科阶段探索强调“我们做”部分的责任逐步释放教学模式的创新教育策略；推广工程和光子学的外展活动将为当地K-12年级的学生举办。在各级，研究计划的基本主题将被纳入教育工作。中红外（MIR）光谱在几乎所有科学学科的传感应用中无处不在。MIR光谱工具主要依赖于频域技术：在MIR光谱系统中，红外光照射样品，并测量透射光的频谱。然后从测量的光谱中提取吸收共振，从而获得有关样品的信息。与传统的MIR光谱相比，在更长的波长下，超快激光系统使时域光谱技术成为可能。例如，在太赫兹时域光谱学中，太赫兹波照射样品，超快激光脉冲被用来测量发射太赫兹辐射的随时间变化的电场。与频域技术相比，这种场分辨测量可以提供独特的动态信息，并显著提高分辨率。该项目的目标是将这种时域、场分辨检测扩展到在MIR中运行的芯片级平台。具体而言，在本项目中，将开发能够分辨入射超快MIR激光脉冲瞬时电场的芯片级光学探测器。这些芯片级探测器将利用来自纳米级金属天线的亚光周期强场光发射电流，在时域内以优异的分辨率对MIR激光脉冲进行采样。这些场分辨探测器将为未来的MIR光谱系统提供革命性的能力，并影响广泛的科学、医学和工业应用。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。

The mid-infrared portion of the electromagnetic spectrum is of fundamental interest to biological, chemical, and physical science. The mid-infrared (MIR) consists of electromagnetic waves with wavelengths from around 3 to 20 millionths of a meter. In this spectral region, virtually all molecules exhibit absorption resonances, and these resonances constitute molecular fingerprints. Accordingly, for around the past hundred years, MIR light has been used for sensing, with recent applications ranging from environmental monitoring to protein characterization. In the past few decades, there have been revolutionary advances in ultrafast MIR laser sources, that is, laser systems producing brief pulses of MIR light. Such ultrafast MIR sources offer new, exciting opportunities for enhancing MIR sensing technologies. The first goal of this project is to develop novel detectors specifically tailored for ultrafast MIR laser sources. These detectors will enable the measurement of light fields of MIR laser pulses in the time-domain. Such field-resolving detectors will enable MIR sensing with improved resolution, as well as provide novel capabilities to study the dynamic behavior of MIR absorption resonances. The second goal of this project is to promote engineering education engineering student retention. Towards this end, online educational content will be developed for graduate students working with ultrafast laser technology; novel educational strategies emphasizing the “we do” component of the gradual release of responsibility pedagogical model will be explored at the undergraduate level; and outreach events, promoting engineering and photonics, will be held for local students at the K-12 level. At all levels, the underlying themes of the research program will be integrated into the educational efforts. Mid-infrared (MIR) spectroscopy is ubiquitous in sensing applications across virtually all scientific disciplines. MIR spectroscopic tools primarily rely on frequency-domain techniques: in a MIR spectroscopic system, infrared light illuminates a sample, and the frequency spectrum of the transmitted light is measured. Absorption resonances are then extracted from the measured spectrum, and information about the sample is thereby obtained. In contrast to conventional MIR spectroscopy, at longer wavelengths, ultrafast laser systems have enabled time-domain spectroscopic techniques. For instance, in terahertz time-domain spectroscopy, terahertz waves irradiate a sample, and ultrafast laser pulses are used to measure the time-dependent electric field of the transmitted terahertz radiation. Such field-resolved measurements can provide unique, dynamical information as well as dramatically improved resolution compared to frequency-domain techniques. The goal of this project is to extend such time-domain, field-resolved detection to chip-scale platforms operating in the MIR. Specifically, in this project, chip-scale, optical detectors capable of resolving the instantaneous electric field of incident ultrafast MIR laser pulses will be developed. These chip-scale detectors will leverage sub-optical-cycle, strong-field photoemission currents from nanoscale metallic antennas to sample MIR laser pulses in the time-domain with exceptional resolution. These field-resolving detectors will provide revolutionary capabilities for future MIR spectroscopic systems and impact a broad range of scientific, medical, and industrial applications.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.