Open AccessDual-frequency imaging using an electrically tunable terahertz quantum cascade laser
Author(s) -
Paul Dean,
Nor Kamila Saat,
Suraj P. Khanna,
Mohammed Salih,
Andrew Burnett,
J. E. Cunningham,
E. H. Linfield,
A. G. Davies
Publication year - 2009
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.17.020631
Subject(s) - terahertz radiation , optics , quantum cascade laser , materials science , attenuation coefficient , terahertz spectroscopy and technology , laser , attenuation , optoelectronics , photomixing , cascade , far infrared laser , physics , terahertz metamaterials , chemistry , chromatography
We report dual-frequency transmission imaging of polycrystalline materials using an electrically tunable terahertz (THz) frequency quantum cascade laser (QCL). Using our system we are able to obtain images at both 3.05 THz and 3.24 THz in a single two-dimensional scan of a sample. By taking the difference of the natural logarithms of the transmission coefficients obtained at each frequency, the difference-attenuation coefficient is determined, and evaluated for samples of lactose monohydrate, glucose monohydrate, sucrose, and the high explosive PETN. We also demonstrate difference-intensity imaging at these frequencies by combining amplitude modulation of the QCL bias with lock-in detection. Owing to the specific molecular absorption spectra of these materials in the THz frequency range, the samples can be distinguished using our technique.