Phase-locked arrays of high-power terahertz lasers with ultra-narrow beams

超窄光束高功率太赫兹激光器锁相阵列

• 批准号: 1609168
• 负责人: Sushil Kumar
• 金额: $ 36.16万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1609168&HistoricalAwards=false
• 关键词: Phase; locked; arrays; power; terahertz

Abstract titleHigh-power terahertz lasers radiating in ultra-narrow beams based on a novel phase-locking scheme for applications in sensing and spectroscopyNon-technical descriptionThe terahertz region of electromagnetic spectrum is significantly underdeveloped due to lack of high-power sources of radiation. Existing monochromatic sources have low output power and/or highly divergent beams, which makes them unsuitable for important applications in terahertz sensing, imaging, and spectroscopy. This project aims to develop terahertz semiconductor lasers that could emit up to hundred milliwatts of average optical power in a narrow beam with less than five degrees of angular divergence. Such a performance is predicted for lasers operated in a compact cryocooler, and will be a significant improvement over present state-of-the-art. A new distributed-feedback scheme that allows phase-locking of multiple terahertz metallic cavities is proposed, which leads to significantly improved radiative efficiencies. The lasers will be developed with the semiconductor quantum-cascade technology that will allow integration of tens of different lasers, each emitting at a range of discrete frequencies, on a single semiconductor chip for broad spectral coverage. The availability of such integrated arrays of high-power terahertz lasers could lead to a transformative impact in the field of terahertz science and technology, by enabling development of cost-effective scientific-instruments for rapid non-invasive/remote sensing, detection, and analysis of a variety of chemicals and biomolecular species such as packaged drugs and explosives, pharmaceutical compounds, and biological samples. There is a strong probability that new business directions will be established in photonics industry if the goals of this project are met successfully. At educational level, the research will be made accessible to undergraduate students especially from diverse backgrounds, who will get hands-on training toward advanced concepts in laser design and characterization, plasmonics, terahertz science, and cryogenic electrical and optical measurements.Technical descriptionCryogenically cooled semiconductor quantum-cascade lasers (QCLs) are the most powerful solid-state sources of coherent terahertz radiation; however, presently, single-mode terahertz lasers operating at practically viable temperatures could only radiate average optical power in the order of a milliwatt, which is insufficient for most targeted applications. This proposal seeks to improve power output from such QCLs by two-orders of magnitude in the range of hundred milliwatts with significantly improved beam quality. A portable electrically operated Stirling cryocooler will provide the required cooling for the semiconductor laser chips that could have tens of such phase-locked QCL arrays emitting at a range of discrete terahertz frequencies. Such a development could lead to commercialization of terahertz QCLs similar to the highly successful mid-infrared QCLs that have spawned recent economic activity in tens of companies worldwide. Terahertz QCLs utilize parallel-plate metallic cavities with strong mode confinement, for which a unique modal coupling scheme for multiple cavities through surface via the surrounding medium (vacuum or air) is proposed. Owing to the very long wavelengths at terahertz frequencies, it is shown that in-phase surface-plasmon-polariton modes for coupled cavities can be excited with periodic photonic structures fabricated using conventional lithography. Radiation in an ultra-narrow beam is expected owing to the spatially extended radiated wavefront of the phased-locked optical mode.Development of high-power terahertz lasers has the potential to enable commercial activity in terahertz spectroscopy, sensing, and imaging. Laser based terahertz instruments could lead to new insights in fields as diverse as cell-biology for study of biomolecular structure and dynamics, non-destructive evaluation and detection of drugs, pharmaceutical products, explosives, non-invasive imaging of biological samples, and remote-sensing of Earth's atmosphere and outer space. A successful outcome of this project will potentially lead to collaborations with industry (specifically, semiconductor laser companies), some of which have shown recent interest for development of terahertz instruments. At the University level, special efforts will be made to involve undergraduate students especially from diverse backgrounds in the research activities during each year.

摘要标题高功率太赫兹激光器辐射在超窄光束的基础上，一种新的相位锁定计划的应用，在传感和spectroscityNon-technical propositionThe太赫兹电磁频谱区域是显着欠发达，由于缺乏高功率的辐射源。现有的单色光源具有低输出功率和/或高度发散的光束，这使得它们不适合太赫兹传感、成像和光谱学中的重要应用。该项目旨在开发太赫兹半导体激光器，该激光器可以在小于5度角发散的窄光束中发射高达100毫瓦的平均光功率。这样的性能预测激光器在紧凑的制冷机中工作，将是一个显着的改进，目前的最先进的。一个新的分布反馈方案，允许多个太赫兹金属腔的相位锁定，这导致显着提高辐射效率。激光器将采用半导体量子级联技术开发，该技术将允许在单个半导体芯片上集成数十个不同的激光器，每个激光器以一系列离散频率发射，以实现广泛的光谱覆盖。这种高功率太赫兹激光器的集成阵列的可用性可能会导致太赫兹科学和技术领域的变革性影响，通过开发具有成本效益的科学仪器，用于快速非侵入性/遥感，检测和分析各种化学品和生物分子物种，如包装药物和爆炸物，药物化合物和生物样品。如果成功实现本项目的目标，将有很大的可能在光电子行业建立新的业务方向。在教育层面上，研究将提供给本科生，特别是来自不同背景的学生，他们将获得实践培训，以实现激光设计和表征，等离子体，太赫兹科学，低温电气和光学测量的先进概念。然而目前，在实际可行的温度下工作的单模太赫兹激光器只能辐射毫瓦量级的平均光功率，这对于大多数目标应用来说是不够的。该提议寻求将来自这样的QCL的功率输出提高两个数量级，在数百毫瓦的范围内，具有显著提高的光束质量。便携式电动斯特林制冷机将为半导体激光器芯片提供所需的冷却，该半导体激光器芯片可以具有数十个这样的锁相QCL阵列，其在离散太赫兹频率范围内发射。这样的发展可能导致太赫兹QCL的商业化，类似于非常成功的中红外QCL，最近在全球数十家公司中产生了经济活动。太赫兹准分子激光器利用具有强模约束的平行板金属腔，提出了一种独特的多腔通过表面和周围介质（真空或空气）的模耦合方案。由于在太赫兹频率的波长很长，它表明，在相位耦合腔的表面等离子体极化激元模式可以激发使用常规光刻制造的周期性光子结构。由于相位锁定光学模式的辐射波前在空间上扩展，期望在超窄光束中辐射。高功率太赫兹激光器的发展具有使太赫兹光谱、传感和成像的商业活动成为可能的潜力。基于激光的太赫兹仪器可以在细胞生物学等不同领域带来新的见解，用于研究生物分子结构和动力学，非破坏性评估和检测药物，药品，爆炸物，生物样品的非侵入性成像以及地球大气层和外层空间的遥感。该项目的成功结果将可能导致与行业（特别是半导体激光器公司）的合作，其中一些公司最近对太赫兹仪器的开发表现出了兴趣。在大学一级，将作出特别努力，让本科生，特别是来自不同背景的本科生参与每年的研究活动。