A terahertz spectrometer on a chip, at the thermodynamical limits

芯片上的太赫兹光谱仪，处于热力学极限

• 批准号: 1810506
• 负责人: Chee Wei Wong
• 金额: $ 39万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1810506&HistoricalAwards=false
• 关键词: terahertz; spectrometer; chip; thermodynamical; limits

Terahertz spectrometry offers a platform for long-distance and non-destructive detection of trace chemicals and gases, explosives, pathogens, and biological agents. These molecules and hazardous agents have unique absorption spectra in the terahertz frequencies, enabling identification of concealed hazardous substances from remote distances. Heterodyne spectrometers are at the frontier for high spectral resolution terahertz spectrometry. Achieved through a number of different techniques such as nonlinear frequency mixing in Schottky diodes, superconductor-insulator-superconductor structures, or hot electron bolometers, they have linewidth-to-center frequency ratios down to one part in a million. These state-of-the-art heterodyne spectrometers and mixers, however, are bulky (weighing tens of kilograms), are bounded by electronic noise far from the fundamental noise limits, and often require cryogenic cooling to reach appreciable sensitivities. This project proposes a chip-scale terahertz spectrometer based on modular integration of a chip-scale laser frequency comb with a chip-scale photomixer. The laser frequency comb consists of discrete optical frequency lines, widely tunable over an octave. The photomixer is based on a plasmonically-enhanced absorbing substrate, directly coupled to a terahertz antenna to collect the incident terahertz radiation. The proposed single-chip terahertz receiver has spectrometry bandwidth of 1-8 THz with spectral resolution better than a kHz, and operates close to the thermodynamical noise limits. The high-performance, low-cost, and compact terahertz spectrometer brings valuable applications in space sciences, biological analysis, environmental studies, pharmaceuticals, and industrial quality control. The proposed scientific efforts are coupled with an outreach and education plan. This involves outreach to underrepresented high-school students and teachers, improvements to the graduate and undergraduate curriculum, and outreach to the general public with focus on underrepresented women and minority students in summer research experiences for undergraduates. The proposed advancement on the heterodyne chip-scale spectrometer consists of three cross-related Thrusts. In Thrust 1, the project will demonstrate an on-chip frequency comb oscillator with wide tuning range of 1-8 THz and comb line-to-line non-uniformity at 0.2 parts per quadrillion when referenced to the optical carrier. In Thrust 2, the project will develop an on-chip integrated pump laser and amplifier, for heterogeneous integration with the photomixer and frequency comb. In Thrust 3, the project will demonstrate the integrated chip-scale heterodyne receiver based on an antenna-coupled plasmonic photomixer. The team seeks to measure a heterodyne photomixer with double-sideband noise sensitivities close to the fundamental bound. The frequency-agile approach is enabled by their recent preliminary studies and measurements close to or at the thermodynamical noise limits. The proposed terahertz spectrometry architecture and scientific Thrusts can transform the platform of terahertz waves for atmospheric studies, space explorations, and safety-industrial-environmental quality control systems. The scientific Thrusts are integrated with educational outreach and cross-disciplinary training efforts. This three-year project will educate a new generation of scientists at the interface of precision chip-scale frequency combs and plasmonic photomixers for transformative terahertz spectrometry near the fundamental bounds.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.

太赫兹光谱仪为远距离和非破坏性检测痕量化学品和气体、爆炸物、病原体和生物制剂提供了平台。这些分子和危险物质在太赫兹频率下具有独特的吸收光谱，能够从远距离识别隐藏的危险物质。外差光谱仪是高光谱分辨率太赫兹光谱测量的前沿。通过许多不同的技术，如肖特基二极管，超导体-绝缘体-超导体结构或热电子测辐射热计中的非线性频率混合，它们的线宽与中心频率比低至百万分之一。然而，这些最先进的外差光谱仪和混频器体积庞大（重数十公斤），受到远离基本噪声极限的电子噪声的限制，并且通常需要低温冷却才能达到可观的灵敏度。本计画提出一种以雷射频率梳与光溷合器模组化整合为基础的晶片级太赫兹光谱仪。激光频率梳由离散的光学频率线组成，可在倍频程上广泛调谐。光混合器基于等离子体增强吸收衬底，直接耦合到太赫兹天线以收集入射的太赫兹辐射。所提出的单芯片太赫兹接收器具有1-8 THz的光谱带宽，光谱分辨率优于kHz，并且接近于物理噪声极限。这种高性能、低成本、紧凑型的太赫兹光谱仪在空间科学、生物分析、环境研究、制药和工业质量控制等领域具有重要的应用价值。拟议的科学工作与一项外联和教育计划相结合。这涉及到对代表性不足的高中学生和教师的外联，改进研究生和本科生课程，以及对公众的外联，重点是代表性不足的妇女和少数民族学生在本科生夏季研究经验。提出的外差芯片级光谱仪的进步包括三个相互关联的推力。在推力1中，该项目将展示一个片上频率梳状振荡器，具有1-8 THz的宽调谐范围和梳状线到线的非均匀性，当参考光载波时，每四倍频程为0.2部分。在第二阶段，该项目将开发一个片上集成泵浦激光器和放大器，用于与光混频和频率梳的异构集成。在第三阶段，该项目将展示基于天线耦合等离子体光混频的集成芯片级外差接收器。该团队试图测量一个外差式光混频器，其双边带噪声灵敏度接近基本边界。频率捷变方法是通过他们最近的初步研究和测量接近或处于物理噪声极限来实现的。提出的太赫兹光谱架构和科学推力可以改变太赫兹波的平台，用于大气研究，空间探索和安全工业环境质量控制系统。科学推力与教育推广和跨学科培训工作相结合。这个为期三年的项目将教育新一代的科学家在精密芯片级频率梳和等离子体光混合器的接口，在基本边界附近的变革太赫兹光谱。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。