Advanced terahertz quantum cascade lasers for frequency comb and mode locking operation

太赫兹（THz）频率范围内的电磁波（1-10太赫兹，1太赫兹= 1E12赫兹）在过去十年中受到了广泛关注，主要是因为它们有可能彻底改变重要应用，包括生物化学物种探测、天文光谱学、太赫兹成像和光学无线通信等。自2002年成立以来，太赫兹量子级联激光器（qcl）由于其紧凑性，高效率和波长可持续性而迅速成为一种有前途的相干光源；然而，在实际应用中适当地调整这些设备有很大的困难，其中最有前途的是高性能光谱学。为了应对这一挑战，拟议的研究计划旨在开发一种基于太赫兹qcl的频率梳装置，以在太赫兹范围内产生稳定和均匀的多波长发射，这将允许高分辨率，易于操作的太赫兹频谱测量。这将为创新奠定基础，这些创新具有强大的潜力，可以更快、更低成本地检测危及生命的疾病（如皮肤癌），在安全检查站更准确、更迅速地筛查危险爆炸物，以及更广泛、更可靠地部署先进的环境监测和保护。该计划旨在解决太赫兹技术实现所固有的基础和技术挑战。目标结合实验和理论方法，并将包括：1)开发太赫兹量子激光器金属-金属脊波导锁相基本物理的综合知识库；2)开发能够数值计算器件材料和波导色散以及增益谱的仿真包；3)设计一个量子有源区，可以产生宽而平坦的增益频谱，并开发一个在宽频率范围内具有零总色散的波导；4)用于频率梳和/或锁模操作的qcl的制造和表征。这项研究的直接成果将是演示一种新型太赫兹频率梳状激光器，从长远来看，这可能会导致第一台用于高功率和高重复率操作的被动锁模太赫兹激光器。该研究将有助于深入理解半导体量子结构的子带间跃迁和啁啾光栅激光波导的锁相机制。制造的设备将在高分辨率太赫兹光谱学、生物和医学科学、太赫兹通信、太赫兹成像等领域产生影响。该研究计划也将为未来知识经济的创新领袖HQP提供良好的培训机会

Electromagnetic waves in the terahertz (THz) frequency range (1-10 THz, 1THz = 1E12 Hz) have received intensive attention over the last decade owing primarily to their potential to revolutionize important applications, including, among many others, bio-chemical species detection, astronomical spectroscopy, terahertz imaging and optical wireless communication. Since their inception in 2002, THz quantum cascade lasers (QCLs) have quickly emerged as a promising coherent light source because of their compactness, high efficiency and wavelength tenability; however, there is significant difficulty in properly adapting these devices for practical applications, the most promising of which is high-performance spectroscopy. In response to this challenge, the proposed research program aims to develop a THz QCL-based frequency comb device to generate stable and uniform multiple-wavelength emissions in the THz range, which would allow high-resolution, easy-to-operate THz spectral measurements. This would lay the groundwork for innovations that have strong potential for much faster and low-cost detection of life-threatening diseases (such as skin cancer), more accurate and expeditious screening of dangerous explosives at security checkpoints, and much wider and reliable deployment of advanced environmental monitoring and protection. ***This proposed program is targeted to tackle the fundamental and technical challenges inherent to bring THz technology to fruition. The objectives combine experimental and theoretical approaches and will include 1) development of a comprehensive knowledge base on the underlying physics of phase locking in the metal-metal ridge waveguide of THz QCLs; 2) development of a simulation package that can numerically calculate the material and waveguide dispersion as well as the gain spectrum of the device; 3) design of a quantum active region that can produce a broad and flat gain spectrum and develop a waveguide with zero overall dispersion over a wide frequency range; 4) fabrication and characterization of QCLs for frequency comb and/or mode-locking operation.***The direct outcome of this research will be the demonstration of a novel terahertz frequency comb laser, which could, in the longer term, lead to the first passive mode-locked THz lasers for high power and high repetition rate operation. The research will develop an in-depth understanding of intersubband transition in semiconductor quantum structures and phase-locking mechanisms in laser waveguide with chirped grating designs. Fabricated devices will carry over impacts in the areas of high-resolution terahertz spectroscopy, biological and medical sciences, terahertz communication, terahertz imaging. The research program will also bring to bear excellent training opportunities for HQP who will lead innovation in tomorrow's knowledge-based economy.**