Terahertz imaging system based on a backward-wave oscillator.
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.
Dobroiu
Adrian
A
RIKEN, The Institute of Physical and Chemical Research, 2-1 Hirosawa, Wakŏ, Saitama 351-0198, Japan. dobroiu@riken.jp
Yamashita
Masatsugu
M
Ohshima
Yuichi N
YN
Morita
Yasuyuki
Y
Otani
Chiko
C
Kawase
Kodo
K
D000818:Animals; D016477:Artifacts; D002645:Chickens; D003952:Diagnostic Imaging / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D008962:Models, Theoretical; D055095:Optics and Photonics; D010944:Plants; D013552:Swine