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

在太赫兹（THz）频率范围（1-10 THz，1 THz = 1 E12 Hz）中的电磁波在过去十年中受到了广泛关注，主要是因为它们具有革命性重要应用的潜力，包括生物化学物种检测、天文光谱学、太赫兹成像和光学无线通信等。自2002年问世以来，太赫兹量子级联激光器（QCL）由于其紧凑性，高效率和波长可调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存在很大困难，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THz QCL的频率梳器件，以在THz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THz光谱测量。这将为创新奠定基础，这些创新具有更快和低成本地检测威胁生命的疾病（如皮肤癌）的巨大潜力，在安全检查站更准确和迅速地筛查危险爆炸物，以及更广泛和可靠地部署先进的环境监测和保护。* 这项拟议的计划旨在解决THz技术实现所固有的基本和技术挑战。目标联合收割机结合实验和理论方法，将包括：1）发展一个全面的知识基础上的基本物理锁定在金属脊波导的太赫兹准分子激光器; 2）发展一个模拟包，可以数值计算的材料和波导色散以及增益谱的设备; 3）量子有源区的设计，该量子有源区可以产生宽而平坦的增益谱，并开发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一种新型太赫兹频率梳状激光器的演示，从长远来看，这可能会导致第一个被动锁模太赫兹激光器的高功率和高重复率操作。该研究将深入了解半导体量子结构中的子带间跃迁和具有啁啾光栅设计的激光波导中的锁相机制。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。该研究计划还将为HQP带来极好的培训机会，他们将在未来的知识经济中领导创新。

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.**