Broadband THz frequency comb generation in quantum cascade lasers

这项提议的科学目标是创造基于室温下工作的量子级联激光光源的太赫兹(THz)频率梳。这项研究将集中在量子级联激光器的创新设计上，以产生数百条均匀分布的太赫兹发射线。在这些激光光源的基础上，PI打算演示一个使用频率梳发射线的光谱系统原型。所提出的器件可能导致基于可批量生产的半导体元件的安全和工业应用的室温光谱仪器。该项目是一个多学科的活动，为参与该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将努力从代表不足的少数民族中招收这些学生，并将通过NSF赞助的UTeachEningeering计划与K-12级别的学生互动。这项提议的目标是获得必要的知识，以创造出具有THz频率梳跨越整个0.5-5 THz范围的室温量子级联激光器。这项研究将专注于创造量子级联激光有源区设计，提供宽带中红外激光增益，用于高效产生中红外频率梳的巨大三阶光学非线性，以及用于中红外频率梳到THz光谱范围高效下转换的巨大二阶非线性。激光波导的设计将实现中红外TM00激光模式的低群速度色散，以及通过切伦科夫差频产生有效的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，对激光器的太赫兹频率梳发射进行线宽测量，并通过迭代设计-制造-测量过程来优化新型低群速度色散量子级联激光波导设计。将展示一种基于量子级联激光光源和外差探测器的原型频率梳光谱系统，例如室温肖特基二极管或低温冷却超导或热电子测辐射热计。

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.