SBIR Phase I: High Contrast Real Time Terahertz Imaging System

该小企业创新研究（SBIR）第一阶段项目的重点是演示实时高对比度太赫兹（THz）成像系统，该系统基于将太赫兹图像上变频到近红外（NIR）光谱范围。由于紧凑太赫兹源的低功率和室温太赫兹探测技术的灵敏度差，在0.3-3太赫兹频率范围内工作的成像系统仍然远不如光学或微波仪器先进。将太赫兹辐射上转换为近红外辐射，可以使用基于更快、更灵敏的近红外探测器和探测器阵列的成像系统。这种技术在过去已经被证明，使用宽带太赫兹结合飞秒近红外脉冲，但这些实时太赫兹图像的对比度是有限的。该项目的目标是在准相位匹配晶体中使用高功率窄带太赫兹和皮秒近红外脉冲的上转换来展示高对比度，实时太赫兹图像。这种方法将提供上转换的太赫兹近红外图像，可以从背景近红外光中进行光谱过滤，显着提高对比度。信号和背景之间的高对比度应该允许使用现成的近红外相机和最近开发的高功率窄带太赫兹源进行实时太赫兹成像。该项目的广泛影响/商业潜力包括用于癌症筛查的太赫兹（THz）成像系统和机场安全系统。毫米波成像系统，工作频率为20-30千兆赫，目前正在机场部署。太赫兹癌症筛查仪器已经进行了几年的试验，在某些类型癌症的早期检测方面显示出很大的希望。太赫兹波不被织物、塑料和许多复合材料大量吸收或散射，在无损评估方面有多种工业和安全应用。几十年来，世界各地的研究人员已经对太赫兹的这些和许多其他潜在应用进行了测试，但很少有太赫兹仪器进入更广泛的科学界，而且今天没有一个在工业中广泛使用。太赫兹成像系统的灵敏度有限，处理时间长，以及不被水吸收的有限光谱带是这些仪器广泛应用的主要障碍。拟议的项目针对所有这些障碍，重点关注1.5太赫兹的水传输窗口，并有可能为更广泛的研究和工业界提供更实用的太赫兹仪器。

This Small Business Innovation Research (SBIR) Phase I project is focused on the demonstration of a real-time high-contrast Terahertz (THz) imaging system, based on frequency upconversion of THz images into the near infrared (NIR) spectral range. Due to low power of compact THz sources and poor sensitivity of room-temperature THz detection techniques, imaging systems operating in 0.3-3 THz range of frequencies remain far less advanced than optical or microwave instruments. Upconversion of THz radiation to NIR enables the use of imaging systems based on faster, more sensitive NIR detectors and detector arrays. This technique has been demonstrated in the past, using broadband THz combined with femtosecond NIR pulses, but the contrast of these real-time THz images was limited. The objective of this project is to demonstrate high contrast, real-time THz images using upconversion of high power narrowband THz and picosecond NIR pulses in quasi-phase matched crystals. This approach will provide upconverted THz-NIR images that can be spectrally filtered from the background NIR light, significantly improving the contrast. The high contrast between signal and background should allow for real time THz imaging using readily available NIR cameras and recently developed high power narrowband THz sources.The broader impact/commercial potential of this project ranges from terahertz (THz) imaging systems for cancer screening to airport security systems. Millimeter wave imaging systems, operating at 20-30 GHz frequencies, are being deployed in airports now. THz cancer screening instruments have been in trials for a few years and have shown great promise in the early detection of certain types of cancers. There are a variety of industrial and security applications for non-destructive evaluation using THz waves, which are not heavily absorbed or scattered by fabrics, plastics and many composite materials. These and many other potential applications of THz have been tested by researchers around the world for decades, but very few THz instruments reached the broader scientific community and none are widely used in the industry today. Limited sensitivity, long processing time of THz imaging systems, and limited spectral bands not absorbed by water are the main barriers for wider applications of these instruments. The proposed project targets all of these barriers, focusing on a water transmission window at 1.5 THz and potentially enabling much more practical THz instruments for a broader research and industrial community.