THz Wave Photonics

太赫兹波光子学伦斯勒理工学院张锡成：自上世纪80年代末S首次展示太赫兹波时域谱后，太赫兹波时域界普遍使用相干发射器和探测器来探测脉冲太赫兹波，主要限于光导偶极子天线和电光晶体。环境空气是一种三阶非线性材料，在产生和探测强飞秒激光脉冲太赫兹波方面应该表现出优异的性能。该项目意义重大，因为可见光在空气中的色散极低，具有全空气发射器和传感器的太赫兹系统可以提供任何其他脉冲太赫兹波传感器所无法提供的带宽，这仅受光脉冲带宽的限制。在空气中，太赫兹波和可见光的衰减分别为100分贝/公里和0.01分贝/公里数量级。由于严重的水蒸气衰减(100分贝/公里)，以前认为不可能进行长距离太赫兹波传感和光谱分析。长距离太赫兹传感现在是可行的，因为通过发送光束在目标附近局部产生和检测太赫兹波，在可见光范围(0.01分贝/公里)实现了低衰减。从而证明，使用空气作为太赫兹波发射器和传感器将为我们在遥感和光谱学方面提供最大的灵活性。更广泛的影响：近年来，随着太赫兹源和更灵敏的探测器开辟了一系列潜在的应用领域，出现了过多的重大进展。半导体表征、无损检测、层析成像、无标记遗传分析、细胞水平成像和化学/生物传感等应用将太赫兹研究从相对默默无闻推向了新的高度。拟议的空气传感器研究将为跨学科研究提供关键的支持技术，并在太赫兹频率范围内推进许多传感和成像概念，对无损分析、国土安全的短期应用和对生物医学的长期兴趣产生直接影响。此外，这项研究将对学生教育、学术研究、外展活动和仪器开发做出重大贡献。

THz Wave Photonics0621522Xi-Cheng Zhang,Rensselaer Polytechnic InstituteIntellectual merit: After the first demonstration of terahertz (THz) wave time-domain spectroscopy in the late 80's, the time-domain THz community commonly uses coherent emitters and detectors for pulsed THz waves, which are mainly limited to the photoconductive dipole antennas and electro-optic crystals. Ambient air, a third-order nonlinear material, should exhibit a remarkable performance for the generation and detection of pulsed THz waves with an intense femtosecond laser beam. The proposed project is significant, since visible light dispersion in air is extremely low, a THz system with an all-air based emitter and sensor could offer a bandwidth unprecedented by any other pulsed THz wave sensor, which is limited only by the optical pulse bandwidth. In the air, the attenuation for THz waves and visible beams are on the order of 100 dB/km and 0.01 dB/km, respectively. It was previously considered impossible to perform long distance THz wave sensing and spectroscopy, due to severe water vapor attenuation (100 dB/km). Long distance THz sensing is now feasible since achieving low attenuation at the visible range (0.01 dB/km) by sending an optical beam to locally generate and detect THz waves near the target. Thus proving that using air as THz wave emitters and sensors would provide us the greatest flexibility in remote sensing and spectroscopy. Broader impact: Recent years have seen a plethora of significant advances as THz sources and more sensitive detectors open up a range of potential applications. Applications including semiconductor characterization, non-destructive testing, tomographic imaging, label-free genetic analysis, cellular level imaging, and chemical/ biological sensing have thrust THz research, from relative obscurity, into new heights. The proposed research on the air sensor will provide a key enabling technology for interdisciplinary research, as well as advance numerous sensing and imaging concepts in the THz frequency range, with an immediate impact on non-destructive analysis, a short-term application for homeland security and a longer-term interest in biomedicine. Moreover, this research will make significant contributions to student education, academic research, outreach activities, and instrumentation development.