Broadband THz frequency comb generation in quantum cascade lasers

本提案的科学目标是在室温下工作的量子级联激光源的基础上创建太赫兹（THz）频率梳。研究将集中在量子级联激光器的创新设计上，以产生数百条均匀间隔的太赫兹发射线。基于这些激光源，PI打算展示一个原型光谱系统使用频率梳发射线。所提出的器件可能导致基于可批量生产的半导体组件的安全和工业应用的室温光谱仪器。这个项目是一个多学科的活动，为参与项目的研究生和本科生提供了一个独特的教育环境。至少有一名研究生和几名本科生将参与这项研究计划。PI将努力从代表性不足的少数民族中招募这些学生，并将通过nsf赞助的uteacheningengineering项目与K-12年级的学生进行互动。本提案的目标是获得必要的知识，以创建室温量子级联激光器，其太赫兹频率梳跨越整个0.5-5太赫兹范围。研究重点是创建量子级联激光有源区设计，提供宽带中红外激光增益，巨大的三阶光学非线性为有效的中红外频率梳生成，以及巨大的二阶非线性为中红外频率梳到太赫兹频谱范围的有效下转换。该激光波导将被设计为实现中红外TM00激光模式的低群速色散，以及通过切伦科夫差频产生的高效太赫兹辐射和外耦合。将研究中红外量子级联激光器中三波和四波混频过程的微妙相互作用，进行激光器太赫兹频率梳状发射的线宽测量，并通过迭代设计-制造-测量过程优化新型低群速色散量子级联激光波导设计。本文演示了一种基于量子级联激光源和外差探测器（如室温肖特基二极管或低温超导或热电子测热计）的频率梳状光谱系统原型。

The scientific objective of this proposal is to create terahertz (THz) frequency combs based on quantum cascade laser sources operating at room-temperature. The research will focus on innovative designs of the quantum cascade laser to produce hundreds of evenly-spaced THz emission lines. Based on these laser sources, the PI intends to demonstrate a prototype spectroscopic system using the frequency-comb emission lines. The proposed devices could lead to room-temperature spectroscopic instrumentation for security and industrial applications based on mass-producible semiconductor components. This project is a multidisciplinary activity that offers a unique educational environment for graduate and undergraduate students involved in the project. At least one graduate student and several undergraduate students will be involved in this research program. The PI will endeavor to recruit these students from underrepresented minorities and will interact with students at the K-12 level through the NSF-sponsored UTeachEningeering program.The objective of this proposal is to attain the necessary knowledge to create room-temperature quantum cascade lasers having THz frequency combs spanning the entire 0.5-5 THz range. The research will focus on creating quantum cascade laser active region design that provides broadband mid-infrared laser gain, giant third-order optical nonlinearity for efficient mid-infrared frequency comb generation, and giant second-order nonlinearity for efficient down-conversion of mid-infrared frequency comb to THz spectral range. The laser waveguide will be designed to enable low group velocity dispersion for mid-infrared TM00 laser modes and efficient terahertz radiation generation and out-coupling via Cherenkov difference-frequency generation. A subtle interplay of three- and four-wave mixing processes in mid-infrared quantum cascade lasers will be investigated, linewidth measurements of terahertz frequency comb emission from the lasers will be performed, and novel low group-velocity-dispersion quantum cascade laser waveguide designs will be optimized via iterative design-fabrication-measurements process. A prototype frequency comb spectroscopic system based on quantum cascade laser sources and a heterodyne detector, such as room-temperature Schottky-diode or cryogenically-cooled superconducting or hot-electron bolometer, is to be demonstrated.