Self-referenced method for terahertz wave time-domain spectroscopy.

The method allows retrieval of the absorbance of a sample without the need for a reference measurement. The method measures the dynamic variation of frequency resolution as the waveform is being acquired. In terahertz wave time-domain spectroscopy, the frequency resolution increases as the temporal window increases. Therefore, narrow absorption peaks will appear in the spectrum when the temporal window is long enough to resolve the peak. By measuring the dynamic values of each frequency component at specific points in time, a reference value and a peak value are extracted and, hence, the self-referenced is achieved. In addition, the method provides a mechanism to remove the effects of echoes, which enables arbitrary temporal window length and, thus, achieves high-resolution frequency. Examples of extraction of the water vapor lines and resonant features in gas and semiconductors are demonstrated in transmission and reflection geometries.

[1]  Cunlin Zhang,et al.  Terahertz wave reference-free phase imaging for identification of explosives , 2008 .

[2]  P. Taday,et al.  Detection and identification of explosives using terahertz pulsed spectroscopic imaging , 2005 .

[3]  G. Bastiaans,et al.  Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz. , 2007, Optics express.

[4]  W. Tribe,et al.  Detection of Concealed Explosives at a Distance Using Terahertz Technology , 2007, Proceedings of the IEEE.

[5]  Weiwei Li,et al.  Identification of chemical materials using reference-free terahertz transmission spectroscopy and artificial neural networks , 2009, International Conference on Optical Instruments and Technology.

[6]  Ole Hirsch,et al.  Techniques for cancellation of interfering multiple reflections in terahertz time-domain measurements , 2008, Microelectron. J..

[7]  Peter Uhd Jepsen,et al.  Investigation of aqueous alcohol and sugar solutions with reflection terahertz time-domain spectroscopy. , 2007, Optics express.

[8]  A. Koch,et al.  Baseline Correction of Spectra in Fourier Transform Infrared: Interactive Drawing with Bézier Curves , 1998 .

[9]  D. Grischkowsky,et al.  Terahertz time-domain spectroscopy of water vapor. , 1989, Optics letters.

[10]  J. Mo,et al.  Baseline correction by improved iterative polynomial fitting with automatic threshold , 2006 .

[11]  M. Hartmann,et al.  Light scattering by small particles. Von H. C. VANDE HULST. New York: Dover Publications, Inc. 1981. Paperback, 470 S., 103 Abb. und 46 Tab., US $ 7.50 , 1984 .

[12]  M. Tani,et al.  A direct comparison between terahertz time-domain spectroscopy and far-infrared Fourier transform spectroscopy , 2001 .