SBIR Phase II: Tunable Terahertz Quantum Cascade Lasers for Spectroscopy

这个小型企业创新研究(SBIR)第二阶段项目将展示一种频率可调的量子级联激光器(TQCL)的原型，该激光器工作在太赫兹频率(2-5 THz)，用于气体光谱和无损成像等应用。这种新型光源是基于分布反馈(DFB)太赫兹QCL的，其侧向波导尺寸远小于波长(线激光器)。这种光学模式延伸到波导外部，允许外部MEMS柱塞与该模式相互作用并影响调谐。低温运行的电机用于使MEMS柱塞偏转，从而实现对输出频率的电子控制。机械、电气、斯塔克频移调谐的组合将允许300 GHz的频率调谐范围和1 MHz的分辨率。TQCL的输出频率将经过粗略校准，允许在软件中选择输出频率。TQCL将安装在一个占地面积较小的制冷机中，输出功率将大于100微瓦。该项目的更广泛影响/商业潜力将是光谱、遥感、天文学和光谱成像中窄气线(MHz)或固体吸收特征(GHz)的检测和表征。这项创新将对学术、工业和政府研究有用。MEMS可调谐光源的电操作和低温系统的交钥匙性质将允许非专业研究人员进入太赫兹光谱区域。未来的用途包括纳入扫描源光学相干层析成像系统进行无损评估(NDE)。太赫兹频率辐射特别适用于无损检测，因为它们能够穿透在红外和可见光波长不透明的材料，如结构泡沫、聚合物和涂料。潜在的应用包括验证航空航天工业中使用的泡沫的结构完整性，持续监测汽车工业中的涂料工艺，以及验证控制释放配方中使用的药物片剂涂层。

This Small Business Innovation Research (SBIR) Phase II project will demonstrate a prototype frequency tunable quantum cascade laser (TQCL) operating at terahertz frequencies (2-5 THz) for applications including gas spectroscopy and non-destructive imaging. This novel source is based on distributed feedback (DFB) terahertz QCL with a lateral waveguide dimension much smaller than the wavelength (wire laser). This optical mode extends outside the waveguide, allowing an external MEMS plunger to interact with the mode and affect tuning. A cryogenically operated motor is used to deflect the MEMS plunger allowing for electronic control of output frequency. A combination of mechanical electrical Stark shift tuning will allow frequency tuning range of 300 GHz with a resolution of 1 MHz. The output frequency of the TQCL will be coarsely calibrated allowing the output frequency to be selected in software. The TQCL will be housed in a small footprint cryocooler, and will have output powers greater than 100 µW.The broader impact/commercial potential of this project will be in detection and characterization of narrow gas lines (MHz) or solid absorption features (GHz) in spectroscopy, remote sensing, astronomy and spectroscopic imaging. The innovation will be useful for academic, industrial and governmental research. The electrical operation of the MEMS tunable source and the turnkey nature of the cryogenic system will allow non-expert researcher access to the terahertz spectral region. Future uses include incorporation into a swept-source optical coherence tomography system for non-destructive evaluation (NDE). Terahertz frequency radiation is of particular interest for use in NDE because they are able to penetrate materials that are opaque at infrared and visible wavelengths such as structural foams, polymers and paints. Potential applications include the validation of the structural integrity of foams used in the aerospace industry, continuous monitoring of paint processes in the automotive industry, and the validation of pharmaceuticals tablet coatings used in controlled release formulations.