Ｆrequency Resolution and Accuracy Improvement of a GaP CW THz Spectrometer
Ｆrequency Resolution and Accuracy Improvement of a GaP CW THz Spectrometer
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GaP 连续太赫兹光谱仪的频率分辨率和精度提高
DOI：
10.1007/978-3-319-46490-9_5
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
and Jun-ichi Nishizawa
中科院分区：
文献类型：
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作者：
Tetsuo Sasaki;Tadao Tanabe;and Jun-ichi Nishizawa
高分辨率太赫兹 (THz) 光谱可用于灵敏的气体检测，也可用于有机分子的振动模式分析。我们开发了一种宽频率可调（0.1-7.5 THz）、单色相干太赫兹波信号发生器，其基础是在小角度非共线相位匹配条件下通过激发声子极化模式在 GaP 晶体中产生差频（DFG）。 DFG 的泵浦光束由半导体激光器提供，经光纤放大器放大后作为种子光束。然后我们将其用作高分辨率和高精度太赫兹光谱仪的光源。结合脉冲管制冷机冷却的超导过渡边缘传感器（TES）测辐射热计，实现了不间断光谱仪系统。该系统具有稳定性高、体积小、操作方便、泵浦激光器寿命期内免维护等优点。由于频率分辨率和精度受到泵浦激光束的限制，我们新开发了两束光同时控制的频率控制系统。通过真空中水蒸气吸收的测量，评估了整个频率可调范围内恒定的 8 MHz 频率分辨率和优于 3 MHz 的绝对精度。
High resolution terahertz (THz) spectroscopy is available for sensitive gas detection and also useful for vibrational mode analysis of organic molecules. We developed a widely frequency tunable (0.1–7.5 THz), monochromatic coherent THz-wave Signal Generator on the basis of difference frequency generation (DFG) in a GaP crystal via excitation of phonon-polariton mode under small-angle non-collinear phase matching condition. The pump beams for DFG were supplied from semiconductor lasers as seed beams after amplification by fiber amplifiers. Then we applied it as a light source for a high resolution and high accuracy THz spectrometer. Combining with a superconducting Transition Edge Sensor (TES) bolometer cooled by a pulse tube refrigerator, a non-stop spectrometer system was realized. The system had advantages of high stability, small size, easy operation and maintenance free in the lifetime of the pump lasers. As frequency resolution and accuracy were limited by those of pump laser beams, we have newly developed a frequency control system for two beams at the same time. Frequency resolution of 8 MHz constant in whole the frequency tunable range and absolute accuracy of better than 3 MHz were evaluated by the measurements of water vapor absorptions in vacuum.