期刊
OPTICS EXPRESS
卷 17, 期 23, 页码 20631-20641出版社
OPTICAL SOC AMER
DOI: 10.1364/OE.17.020631
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资金
- EPSRC (UK)
- EC
- Government of Malaysia
- Her Majesty's Government Communications Centre
- Defence Science and Technology Laboratory
- HM Revenue and Customs
- Home Office Scientific Development Branch
- Forensic Science Service.
- Engineering and Physical Sciences Research Council [GR/S51417/01, EP/E048811/1] Funding Source: researchfish
- EPSRC [EP/E048811/1] Funding Source: UKRI
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. (C) 2009 Optical Society of America
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