SBIR Phase II: Tunable Terahertz Quantum Cascade Lasers for Spectroscopy

这个小企业创新研究（SBIR）二期项目将展示一个工作在太赫兹频率（2-5太赫兹）的可调频率量子级联激光器（TQCL）原型，用于气体光谱和非破坏性成像等应用。这种新型光源基于分布反馈（DFB）太赫兹QCL，其横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之外，允许外部MEMS柱塞与模式相互作用并影响调谐。低温操作电机用于偏转MEMS柱塞，允许电子控制输出频率。机械电气斯塔克移位调谐的组合将允许频率调谐范围为300 GHz，分辨率为1 MHz。TQCL的输出频率将被粗略校准，允许在软件中选择输出频率。TQCL将被安置在一个小体积的制冷机中，输出功率将大于100µW。这个项目更广泛的影响/商业潜力将是在光谱学、遥感、天文学和光谱成像方面探测和表征狭窄气体线（兆赫）或固体吸收特征（千兆赫）。这一创新将有助于学术、工业和政府研究。MEMS可调谐源的电气操作和低温系统的交钥匙特性将允许非专业研究人员访问太赫兹光谱区域。未来的应用包括纳入扫描源光学相干层析成像系统，用于无损评估（NDE）。太赫兹频率辐射在无损检测中特别有意义，因为它们能够穿透在红外和可见光波段不透明的材料，如结构泡沫、聚合物和油漆。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，汽车工业中油漆过程的连续监测，以及用于控释配方的药物片剂涂层的验证。

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.