Dobroiu Adrian, Yamashita Masatsugu, Ohshima Yuichi N, Morita Yasuyuki, Otani Chiko, Kawase Kodo
RIKEN, The Institute of Physical and Chemical Research, 2-1 Hirosawa, Wakŏ, Saitama 351-0198, Japan.
Appl Opt. 2004 Oct 20;43(30):5637-46. doi: 10.1364/ao.43.005637.
We present an imaging system designed for use in the terahertz range. As the radiation source a backward-wave oscillator was chosen for its special features such as high output power, good wave-front quality, good stability, and wavelength tunability from 520 to 710 GHz. Detection is achieved with a pyroelectric sensor operated at room temperature. The alignment procedure for the optical elements is described, and several methods to reduce the etalon effect that are inherent in monochromatic sources are discussed. The terahertz spot size in the sample plane is 550 microm (nearly the diffraction limit), and the signal-to-noise ratio is 10,000:1; other characteristics were also measured and are presented in detail. A number of preliminary applications are also shown that cover various areas: nondestructive real-time testing for plastic tubes and packaging seals; biological terahertz imaging of fresh, frozen, or freeze-dried samples; paraffin-embedded specimens of cancer tissue; and measurement of the absorption coefficient of water by use of a wedge-shaped cell.
我们展示了一种设计用于太赫兹波段的成像系统。作为辐射源，选用了返波振荡器，因其具有高输出功率、良好的波前质量、良好的稳定性以及520至710吉赫兹的波长可调性等特殊特性。采用在室温下工作的热释电传感器进行探测。描述了光学元件的对准程序，并讨论了几种减少单色源中固有干涉仪效应的方法。样品平面中的太赫兹光斑尺寸为550微米（接近衍射极限），信噪比为10000:1；还测量了其他特性并进行了详细介绍。还展示了一些初步应用，涵盖多个领域：塑料管材和包装密封的无损实时检测；新鲜、冷冻或冻干样品的生物太赫兹成像；癌组织的石蜡包埋标本；以及使用楔形池测量水的吸收系数。
