Article

Characterization of aqueous alcohol solutions in bottles with THz reflection spectroscopy

DTU Fotonik-Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
Optics Express (Impact Factor: 3.49). 07/2008; 16(13):9318-31. DOI: 10.1364/OE.16.009318
Source: PubMed

ABSTRACT

We demonstrate a method based on self-referenced THz time-domain spectroscopy for inspection of aqueous liquids, and in particular alcohol solutions, inside closed containers. We demonstrate that it is possible to determine the alcohol content of an aqueous solution, and that liquids can be classified as either harmless or inflammable. The method operates in reflection mode with the result that liquids opaque to THz radiation can be characterized with little influence of the bottle shape. The method works with plastic bottles as well as glass bottles, with absorption of THz radiation by the plastic or the glass being the limiting factor. The reflection mode allows for automatic control of the validity of the measurement. The method will be useful in liquid scanning systems at security checkpoints.

  • Source
    • "First and foremost, the liquid explosives receive much attention, as no other systems exist for their reliable recognition. Recently, Jepsen and co-workers have shown that liquids inside closed containers can be classified as either harmless or inflammable based on self-referenced THz TDS [21]. Here, we focus on developing a handheld security scanner for identifying suspicious liquids at airports. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Terahertz time-domain spectroscopy (THz TDS) holds high potential as a non-destructive, non-contact testing tool. We have identified a plethora of emerging industrial applications such as quality control of industrial processes and products in the plastics industry. Polymers are transparent to THz waves while additives show a significantly higher permittivity. This dielectric contrast allows for detecting the additive concentration and the degree of dispersion. We present a first inline configuration of a THz TDS spectrometer for monitoring polymeric compounding processes. To evaluate plastic components, non-destructive testing is strongly recommended. For instance, THz imaging is capable of inspecting plastic weld joints or revealing the orientation of fiber reinforcements. Water strongly absorbs THz radiation. However, this sensitivity to water can be employed in order to investigate the moisture absorption in plastics and the water content in plants. Furthermore, applications in food technology are discussed. Moreover, security scanning applications are addressed in terms of identifying liquid explosives. We present the vision and first components of a handheld security scanner. In addition, a new approach for parameter extraction of THz TDS data is presented. All in all, we give an overview how industry can benefit from THz TDS completing the tool box of non-destructive evaluation.
    Full-text · Article · Jul 2009 · Proceedings of SPIE - The International Society for Optical Engineering
  • Source
    • "In recent years terahertz time-domain spectroscopy [1] [2] has gained popularity in basic research and in applications such as quality control [3]–[8] and national security [9]–[11]. The technique is based on the principle of optical excitation of a semiconductor substrate on which a metal structure is deposited. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we study the effect of the length of dipole antennas on the spectrum of the radiated THz signal in pulse-excited opto-electronic terahertz systems. In particular, we investigate the origin of the commonly observed sharp dips that occur in the spectra of photoconductive dipole antennas, and explain them on the basis of reflections of the excitation current pulse that take place at the ends of the antenna. We develop a hybrid time-domain model for the system and show that the predictions of our model are in good agreement with experimental results.
    Full-text · Article · Jan 2009 · Journal of the European Optical Society Rapid Publications
    • "In recent years terahertz time-domain spectroscopy [1] [2] has gained popularity in basic research and in applications such as quality control [3]–[8] and national security [9]–[11]. The technique is based on the principle of optical excitation of a semiconductor substrate on which a metal structure is deposited. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we show that the real emission frequency of a photoconductive dipole antenna operating in conjunction with photomixers is not its natural resonant frequency, but a frequency where the antenna's input resistance is the highest and the corresponding mismatch with the source is the smallest. We also introduce a new kind of antenna that offers a much higher input resistance to the photomixer and hence enhances the efficiency of the continuous-wave system.
    No preview · Article · Apr 2006 · Proceedings of SPIE - The International Society for Optical Engineering
Show more