Abstract

We present terahertz (THz) reflective spectroscopic focal-plane imaging of four explosive and bio-chemical materials (2, 4-DNT, Theophylline, RDX and Glutamic Acid) at a standoff imaging distance of 0.4 m. The 2 dimension (2-D) nature of this technique enables a fast acquisition time and is very close to a camera-like operation, compared to the most commonly used point emission-detection and raster scanning configuration. The samples are identified by their absorption peaks extracted from the negative derivative of the reflection coefficient respect to the frequency (-dr/dv) of each pixel. Classification of the samples is achieved by using minimum distance classifier and neural network methods with a rate of accuracy above 80% and a false alarm rate below 8%. This result supports the future application of THz time-domain spectroscopy (TDS) in standoff distance sensing, imaging, and identification.

© 2006 Optical Society of America

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2005

Y. Shen, P. Taday, D. Newnham, and M. Pepper, "Chemical mapping using reflection terahertz pulsed imaging," Semicond. Sci. Technol. 20, S254-257 (2005).
[CrossRef]

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

2004

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

M. K. Choi, A. Bettermann, and D. W. van der Weide, "Potential for detection of explosive and biological hazards with electronic terahertz systems," Phil. Trans. R. Soc. Lond. A 362, 337-349 (2004).
[CrossRef]

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

2003

R. Rungsawang, K. Ohta, K. Tukamoto, and T. Hattori, "Ring formation of focused half-cycle terahertz pulses," J. Phys. D: Appl. Phys. 36229-235 (2003).
[CrossRef]

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

J. Xu, T. Yuan, S. Mickan, and X.-C. Zhang, "Limit of spectral resolution in terahertz time-domain spectroscopy," Chin. Phys. Lett. 20, 1266-1268 (2003).
[CrossRef]

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

2002

F. Ferguson, S. Wang, D. Gray, D. Abbot and X.-C. Zhang, "T-ray computed tomography," Opt. Lett. 27, 1312-1314 (2002).
[CrossRef]

B. Ferguson, and X.-C. Zhang, "Materials for terahertz science and technology," Nat. Mater. 1, 26-33 (2002).
[CrossRef]

1999

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

1998

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

1997

1996

Q. Wu, T. Hewitt, and X.-C. Zhang, "Two-dimensional electro-optic imaging of THz beams," Appl. Phys. Lett. 69, 1026-1028 (1996).
[CrossRef]

1994

Abbot, D.

Altan, H.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Arnone, D.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Baraniuk, R. G.

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

Barat, R.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Bettermann, A.

M. K. Choi, A. Bettermann, and D. W. van der Weide, "Potential for detection of explosive and biological hazards with electronic terahertz systems," Phil. Trans. R. Soc. Lond. A 362, 337-349 (2004).
[CrossRef]

Boivin, L.

Bykhovskaia, M.

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

Chen, M.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Choi, M. K.

M. K. Choi, A. Bettermann, and D. W. van der Weide, "Potential for detection of explosive and biological hazards with electronic terahertz systems," Phil. Trans. R. Soc. Lond. A 362, 337-349 (2004).
[CrossRef]

Cole, B.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Federici, J. F.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Ferguson, B.

B. Ferguson, and X.-C. Zhang, "Materials for terahertz science and technology," Nat. Mater. 1, 26-33 (2002).
[CrossRef]

Ferguson, F.

Fukushima, M. K.

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

Gary, D.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Gelmont, B.

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

Globus, T.

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

Gray, D.

Gupta, M.

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

Hangyo, M.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Hattori, T.

R. Rungsawang, K. Ohta, K. Tukamoto, and T. Hattori, "Ring formation of focused half-cycle terahertz pulses," J. Phys. D: Appl. Phys. 36229-235 (2003).
[CrossRef]

Hewitt, T.

Q. Wu, T. Hewitt, and X.-C. Zhang, "Two-dimensional electro-optic imaging of THz beams," Appl. Phys. Lett. 69, 1026-1028 (1996).
[CrossRef]

Huang, F.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Hunsche, S.

Ikari, T.

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

Ikeda, T.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Ino, Y.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

Ishida, H.

Ishikawa, Y.

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

Ito, H.

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

Jacobsen, R. H.

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

Kawase, K.

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

Koch, M.

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

Koide, K.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Kuwata-Gonokami, M.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

Linfield, E.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Madaras, E.

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

Masui, A.

Matsushita, A.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Mickan, S.

J. Xu, T. Yuan, S. Mickan, and X.-C. Zhang, "Limit of spectral resolution in terahertz time-domain spectroscopy," Chin. Phys. Lett. 20, 1266-1268 (2003).
[CrossRef]

Minami, Y.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Minamide, H.

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

Mittleman, D. M.

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

D. M. Mittleman, S. Hunsche, L. Boivin, and M. C. Nuss, "T-ray tomography," Opt. Lett. 22, 904-906 (1997).
[CrossRef] [PubMed]

Miyamaru, F.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Neelamani, R.

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

Newnham, D.

Y. Shen, P. Taday, D. Newnham, and M. Pepper, "Chemical mapping using reflection terahertz pulsed imaging," Semicond. Sci. Technol. 20, S254-257 (2005).
[CrossRef]

Nuss, M. C.

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

D. M. Mittleman, S. Hunsche, L. Boivin, and M. C. Nuss, "T-ray tomography," Opt. Lett. 22, 904-906 (1997).
[CrossRef] [PubMed]

Ohta, K.

R. Rungsawang, K. Ohta, K. Tukamoto, and T. Hattori, "Ring formation of focused half-cycle terahertz pulses," J. Phys. D: Appl. Phys. 36229-235 (2003).
[CrossRef]

Otani, C.

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

Peiponen, K.-E.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

Pepper, M.

Y. Shen, P. Taday, D. Newnham, and M. Pepper, "Chemical mapping using reflection terahertz pulsed imaging," Semicond. Sci. Technol. 20, S254-257 (2005).
[CrossRef]

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Pye, R.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Reightler, T. Y. R.

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

Rudd, J. V.

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

Rungsawang, R.

R. Rungsawang, K. Ohta, K. Tukamoto, and T. Hattori, "Ring formation of focused half-cycle terahertz pulses," J. Phys. D: Appl. Phys. 36229-235 (2003).
[CrossRef]

Samuels, A.

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

Schulkin, B.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Shen, Y.

Y. Shen, P. Taday, D. Newnham, and M. Pepper, "Chemical mapping using reflection terahertz pulsed imaging," Semicond. Sci. Technol. 20, S254-257 (2005).
[CrossRef]

Shimano, R.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

Svirko, Y. P.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

Taday, P.

Y. Shen, P. Taday, D. Newnham, and M. Pepper, "Chemical mapping using reflection terahertz pulsed imaging," Semicond. Sci. Technol. 20, S254-257 (2005).
[CrossRef]

Tani, M.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Tanner, D. B.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Tatsuno, M.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Tukamoto, K.

R. Rungsawang, K. Ohta, K. Tukamoto, and T. Hattori, "Ring formation of focused half-cycle terahertz pulses," J. Phys. D: Appl. Phys. 36229-235 (2003).
[CrossRef]

Usami, M.

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

van der Weide, D. W.

M. K. Choi, A. Bettermann, and D. W. van der Weide, "Potential for detection of explosive and biological hazards with electronic terahertz systems," Phil. Trans. R. Soc. Lond. A 362, 337-349 (2004).
[CrossRef]

Vartiainen, E. M.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

Wallace, V.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Wang, S.

Watanabe, Y.

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

Werbos, L.

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

Woodward, R.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

Woolard, D.

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

Wu, Q.

Q. Wu, T. Hewitt, and X.-C. Zhang, "Two-dimensional electro-optic imaging of THz beams," Appl. Phys. Lett. 69, 1026-1028 (1996).
[CrossRef]

Xie, X.

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

Xu, J.

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

J. Xu, T. Yuan, S. Mickan, and X.-C. Zhang, "Limit of spectral resolution in terahertz time-domain spectroscopy," Chin. Phys. Lett. 20, 1266-1268 (2003).
[CrossRef]

Yamaguchi, M.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Yamamoto, K.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

K. Yamamoto, A. Masui and H. Ishida, "Kramers-Kronig analysis of infrared reflection spectra with perpendicular polarization," Appl. Opt. 33, 6285-6293 (1994).
[CrossRef] [PubMed]

Yamashita, M.

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

Yuan, T.

J. Xu, T. Yuan, S. Mickan, and X.-C. Zhang, "Limit of spectral resolution in terahertz time-domain spectroscopy," Chin. Phys. Lett. 20, 1266-1268 (2003).
[CrossRef]

Zhang, X.-C.

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

J. Xu, T. Yuan, S. Mickan, and X.-C. Zhang, "Limit of spectral resolution in terahertz time-domain spectroscopy," Chin. Phys. Lett. 20, 1266-1268 (2003).
[CrossRef]

B. Ferguson, and X.-C. Zhang, "Materials for terahertz science and technology," Nat. Mater. 1, 26-33 (2002).
[CrossRef]

F. Ferguson, S. Wang, D. Gray, D. Abbot and X.-C. Zhang, "T-ray computed tomography," Opt. Lett. 27, 1312-1314 (2002).
[CrossRef]

Q. Wu, T. Hewitt, and X.-C. Zhang, "Two-dimensional electro-optic imaging of THz beams," Appl. Phys. Lett. 69, 1026-1028 (1996).
[CrossRef]

Zhong, H.

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

Zimdars, D.

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Appl. Opt.

Appl. Phys. B

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, and M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
[CrossRef]

D. M. Mittleman, R. H. Jacobsen, R. Neelamani, R. G. Baraniuk, and M. C. Nuss, "Gas sensing using terahertz time-domain spectroscopy," Appl. Phys. B 67, 379-390 (1998).
[CrossRef]

Appl. Phys. Lett.

Q. Wu, T. Hewitt, and X.-C. Zhang, "Two-dimensional electro-optic imaging of THz beams," Appl. Phys. Lett. 69, 1026-1028 (1996).
[CrossRef]

M. Usami, M. Yamashita, M. K. Fukushima, C. Otani, and K. Kawase, "Terahertz wideband spectroscopic imaging based on two-dimensional electro-optic sampling technique," Appl. Phys. Lett. 86, 141109-1-3 (2005).
[CrossRef]

Y. Watanabe, K. Kawase, T. Ikari, H. Ito, Y. Ishikawa, and H. Minamide, "Component spatial pattern analysis of chemicals using terahertz spectroscopic imaging," Appl. Phys. Lett. 83, 800-802 (2003).
[CrossRef]

F. Huang, B. Schulkin, H. Altan, J. F. Federici, D. Gary, R. Barat, D. Zimdars, M. Chen, and D. B. Tanner, "Terahertz study of 1,3,5-trinitro-s-triazine by time-domain and Fourier transform infrared spectroscopy," Appl. Phys. Lett. 85, 5535-5537 (2004).
[CrossRef]

Chin. Phys. Lett.

J. Xu, T. Yuan, S. Mickan, and X.-C. Zhang, "Limit of spectral resolution in terahertz time-domain spectroscopy," Chin. Phys. Lett. 20, 1266-1268 (2003).
[CrossRef]

IEEE Sens. J

H. Zhong, J. Xu, X. Xie, T. Y. R. Reightler, E. Madaras, and X.-C. Zhang, "Nondestructive defect identification with terahertz time-of-flight tomography," IEEE Sens. J.  5, 203-208 (2005).
[CrossRef]

International Journal of High Speed Electronics and Systems

T. Globus, D. Woolard, M. Bykhovskaia, B. Gelmont, L. Werbos, and A. Samuels, "THz-frequency spectroscopic sensing of DNA and related biological materials," International Journal of High Speed Electronics and Systems,  13, 903-936 (2003).
[CrossRef]

J. Appl. Phys.

E. M. Vartiainen, Y. Ino, R. Shimano, M. Kuwata-Gonokami, Y. P. Svirko, and K.-E. Peiponen, "Numerical phase correction method for terahertz time-domain reflection spectroscopy," J. Appl. Phys. 96, 4171-4175 (2004).
[CrossRef]

J. Invest. Dermatol.

R. Woodward, V. Wallace, R. Pye, B. Cole, D. Arnone, E. Linfield, and M. Pepper, "Terahertz pulse imaging of ex vivo basal cell carcinoma samples," J. Invest. Dermatol. 120, 72-78 (2003).
[CrossRef] [PubMed]

J. Phys. D: Appl. Phys.

R. Rungsawang, K. Ohta, K. Tukamoto, and T. Hattori, "Ring formation of focused half-cycle terahertz pulses," J. Phys. D: Appl. Phys. 36229-235 (2003).
[CrossRef]

Jpn. J. Appl. Phys.

K. Yamamoto, M. Yamaguchi, F. Miyamaru, M. Tani, M. Hangyo, T. Ikeda, A. Matsushita, K. Koide, M. Tatsuno and Y. Minami, "Noninvasive inspection of C-4 explosive in mails by terahertz time-domain spectroscopy," Jpn. J. Appl. Phys. 43, n 3B, L414-417 (2004).
[CrossRef]

Nat. Mater.

B. Ferguson, and X.-C. Zhang, "Materials for terahertz science and technology," Nat. Mater. 1, 26-33 (2002).
[CrossRef]

Opt. Lett.

Phil. Trans. R. Soc. Lond. A

M. K. Choi, A. Bettermann, and D. W. van der Weide, "Potential for detection of explosive and biological hazards with electronic terahertz systems," Phil. Trans. R. Soc. Lond. A 362, 337-349 (2004).
[CrossRef]

Semicond. Sci. Technol.

Y. Shen, P. Taday, D. Newnham, and M. Pepper, "Chemical mapping using reflection terahertz pulsed imaging," Semicond. Sci. Technol. 20, S254-257 (2005).
[CrossRef]

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B. Ferguson, "Three-dimensional T-ray inspection systems," Ph.D. thesis (2003).

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[CrossRef]

D. Zimdars, J. White, G. Stuk, A. Chernovsky, G. Fichter, and S. Williamson, "Large area high speed time domain THz imager for security and nondestructive evaluation imaging," the Joint 30th International Conference on Infrared and Millimeter Waves, 1, 5-6 (2005).
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H. Zhong, A. Redo, Y. Chen, and X.-C. Zhang, "Standoff distance detection of explosive materials with THz waves," the Joint 30th International Conference on Infrared and Millimeter Waves, 1, 42-3 (2005).
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[CrossRef]

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Figures (9)

Fig. 1.
Fig. 1.

The absorption coefficient κ and -dr/dν of RDX. Both curves show the absorption peak around 0.82 THz and 1.05 THz, which are indicated by arrows.

Fig. 2.
Fig. 2.

Experimental-set up of THz reflective spectroscopic focal-plane imaging system.

Fig. 3.
Fig. 3.

The extinction coefficient κ of RDX, Theophylline, 2, 4-DNT, and Glutamic Acid measured by transmission THz-TDS in nitrogen purged cell. Data is shifted for clarity. The arrows indicate the absorption peaks of each target.

Fig. 4.
Fig. 4.

Time domain waveform (top) and spectrum (bottom) of the reference THz wave (averaged over all pixels).

Fig. 5.
Fig. 5.

Optical picture of 2, 4-DNT, Theopylline, RDX, Glutamic Acid and glass sample target.

Fig. 6.
Fig. 6.

THz peak amplitude image of 2, 4-DNT, Theophylline RDX, Glutamic Acid and glass. Identification of the samples is not possible in this image.

Fig. 7.
Fig. 7.

-dr/dv of RDX, Theophylline, 2, 4-DNT, Glutamic Acid and glass from five randomly selected pixels on each sample image. The arrows indicate the absorption peaks. Three absorption peaks of RDX, one of 2, 4-DNT and one of Glutamic Acid are located by comparing with Fig 6.2. No significant absorption features are found in Theophylline’s plot.

Fig. 8.
Fig. 8.

The images of the sample targets formed by integrating the peak area around (a) 0.82 THz; (b) 0.96 THz; (c) 1.08 THz and (d) 1.21 THz, with a width of 0.15 THz. Except for the image at 0.96 THz, which is supposed to be the absorption peak location of Theophylline, all three other samples can be identified at the images of their corresponding absorption peak frequencies.

Fig. 9.
Fig. 9.

Histogram of the spectroscopic image at 1.21 THz on Fig. 8 (d). The pixel value is normalized from 1 to 10. The position of the peak on the left Ifloor represents the pixel value of the background, whereas the position of the peak on the right Ipeak indicates the pixel value of the foreground, which is the sample being identified.

Tables (3)

Tables Icon

Table 1. Contrast of each image on Fig. 8. The image at 0.82 THz has the highest contrast because the extinction coefficient κ of RDX is measured to be the highest among the four. The image at 0.96 THz has zero contrast resulting from the single normal distribution on its histogram. The failure to identify any absorption feature at 0.96 THz image is due to insufficient dynamic range of the imaging system.

Tables Icon

Table 2. Positive (P), negative (W) and false (F) identification percentage of the classification using the first derivative of reflective coefficient -dr/dv.

Tables Icon

Table 3. Positive (P), negative (W) and false (F) identification rate using both A and B criteria.

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

r ˜ = E 2 E 1 = n ˜ 1 n ˜ + 1 = ( n 1 ) + i κ ( n + 1 ) + i κ = R e i ϕ
n = 1 + R 1 + R 2 R cos ϕ κ = 2 R sin ϕ 1 + R 2 R cos ϕ
v 1 v 2 dr dv dv = r v 2 r v 1 = Δ r
C = ( I peak I floor ) ( I peak + I floor )
d i x = ( x μ i ) T i 1 ( x μ i )
P i = r i N i , W i = t i N i , N i = r i + t i + o i , F i = u i N , N = i N i
Δ r δ r > SNR D > SNR · r Δ r

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