Abstract

We report diffuse reflection imaging in air of concealed powdered samples using a terahertz quantum cascade laser. The sensitivity of the detection scheme to sub-surface absorption within samples is confirmed using fully-characterized powdered admixtures of polystyrene and polymethyl methacrylate (PMMA). Measurements of the backscattering intensity from these samples are then used in conjunction with Kubelka-Munk scattering theory, as well as several models based on the quasi-crystalline approximation, to extract the absorption coefficient of PMMA. Our research demonstrates the feasibility of high-resolution frequency-domain terahertz imaging for the detection and identification of concealed powders in a reflection geometry.

© 2008 Optical Society of America

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2008 (1)

2007 (2)

J. Chen, Y. Chen, H. Zhao, G. J. Bastiaans, and X.-C. Zhang, "Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz," Opt. Express 15, 12060-12067 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-19-12060.
[CrossRef] [PubMed]

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

2006 (5)

H-B. Liu, Y. Chen, G. J. Bastiaans, and X.-C. Zhang, "Detection and identification of explosive RDX by THz diffuse reflection spectroscopy," Opt. Express 14, 415-423 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-1-415.
[CrossRef] [PubMed]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, "High-power quantum cascade lasers," Electron. Lett. 42, 89-90 (2006).
[CrossRef]

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

K. L. Nguyen, M. L. Johns, L. F. Gladden, C. H. Worrall, P. Alexander, H. E. Beere, M. Pepper, D. A.  Ritchie, J. Alton, S. Barbieri, and E. H. Linfield, "Three-dimensional imaging with a terahertz quantum cascade laser," Opt. Express 14, 2123-2129 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-6-2123.
[CrossRef] [PubMed]

2005 (3)

2004 (5)

D. J. Cook, B. K. Decker, G. Dadusc, and M. G. Allen, "Through container THz sensing: applications for bio detection," in Int. Soc. Opt. Eng.Proc. SPIE 5268, 36-42 (2004).

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

E. Pickwell, B. E. Cole, A. J. Fitzgerald, and V. P. Wallace, "Simulation of terahertz pulse propagation in biological systems," Appl. Phys. Lett. 84, 2190-2192 (2004).
[CrossRef]

A. Dobroiu, M. Yamashita, Y. N. Oshima, Y. Morita, C. Otani, and K. Kawase, "Terahertz imaging system based on a backward-wave oscillator," Appl. Opt. 43, 5637-5646 (2004).
[CrossRef] [PubMed]

S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "2.9 THz quantum cascade laser operating at 70 K in continuous wave," Appl. Phys. Lett. 85, 1674-1676 (2004).
[CrossRef]

2003 (3)

J. Pearce, Z. Jian, and D. M. Mittleman, "Statistics of multiply scattered broadband terahertz pulses," Phys. Rev. Lett. 91, 043903-1-4 (2003).
[CrossRef] [PubMed]

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]

K. Kawase, Y. Ogawa, Y. Watanabe, and H. Inoue, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Express 11, 2549-2554 (2003), http://www.opticsinfobase.org/abstract.cfm?URI=oe-11-20-2549.
[CrossRef] [PubMed]

2002 (1)

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

2001 (2)

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

J. Pearce and D. M. Mittleman, "Propagation of single-cycle terahertz pulses in random media," Opt. Lett.  26, 2002-2004 (2001).
[CrossRef]

1996 (1)

P. R. Siqueira and K. Sarabandi, "Method of moments evaluation of the two-dimensional quasi-crystalline approximation," IEEE Trans. Antenn. Prop. 44, 1067-1077 (1996).
[CrossRef]

1995 (1)

1994 (1)

1992 (1)

J. R. Birch, "The far-infrared optical constants of polypropylene, PTFE and polystyrene," Infrared Phys. 33, 33-38 (1992).
[CrossRef]

1987 (1)

1963 (2)

M. S. Wertheim, "Exact solution of the Percus-Yevick integral equation for hard spheres," Phys. Rev. Lett.  10, 321-323 (1963).
[CrossRef]

L. Tsang and J. A. Kong, "Scattering of electromagnetic waves from a half space of densely distributed dielectric scatterers," Radio Science 18, 1260-1272 (1963).
[CrossRef]

1954 (1)

1952 (1)

M. Lax, "Multiple scattering of waves. II. The effective field in dense systems," Phys. Rev. 85, 621-629 (1952).
[CrossRef]

1945 (1)

L. L. Foldy, "The multiple scattering of waves. I. General theory of isotropic scattering by randomly distributed scatterers" Phys. Rev. 67, 107-119 (1945).
[CrossRef]

1931 (1)

P. Kubelka and F. Munk, "Ein beitrag zur optic der fabanstriche," Z. Tech. Physik 12, 593-601 (1931).

Alexander, P.

Allen, M. G.

D. J. Cook, B. K. Decker, G. Dadusc, and M. G. Allen, "Through container THz sensing: applications for bio detection," in Int. Soc. Opt. Eng.Proc. SPIE 5268, 36-42 (2004).

Alton, J.

Arnone, D. D.

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

Baker, C.

Barbieri, S.

Bastiaans, G. J.

Beere, H. E.

Belkin, M. A.

Berry, E.

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

Birch, J. R.

J. R. Birch, "The far-infrared optical constants of polypropylene, PTFE and polystyrene," Infrared Phys. 33, 33-38 (1992).
[CrossRef]

Breede, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Burnett, A.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Capasso, F.

Chamberlain, J. M.

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

Chen, J.

Chen, Y.

Cole, B. E.

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[CrossRef]

E. Pickwell, B. E. Cole, A. J. Fitzgerald, and V. P. Wallace, "Simulation of terahertz pulse propagation in biological systems," Appl. Phys. Lett. 84, 2190-2192 (2004).
[CrossRef]

Coltman, J.

Cook, D. J.

D. J. Cook, B. K. Decker, G. Dadusc, and M. G. Allen, "Through container THz sensing: applications for bio detection," in Int. Soc. Opt. Eng.Proc. SPIE 5268, 36-42 (2004).

Cunningham, J.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Dadusc, G.

D. J. Cook, B. K. Decker, G. Dadusc, and M. G. Allen, "Through container THz sensing: applications for bio detection," in Int. Soc. Opt. Eng.Proc. SPIE 5268, 36-42 (2004).

Davies, A. G.

M. A. Belkin, J. A. Fan, S. Hormoz, F. Capasso, S. P. Khanna, M. Lachab, A. G. Davies, and E. H. Linfield, "Terahertz quantum cascade lasers with copper metal-metal waveguides operating up to 178 K," Opt. Express 16, 3242-3248 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-5-3242.
[CrossRef] [PubMed]

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Decker, B. K.

D. J. Cook, B. K. Decker, G. Dadusc, and M. G. Allen, "Through container THz sensing: applications for bio detection," in Int. Soc. Opt. Eng.Proc. SPIE 5268, 36-42 (2004).

Dobroiu, A.

Donhuijsen, K.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Douglass, R. E.

Edwards, H.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Faist, J.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Fan, J. A.

Fan, W.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Fitzgerald, A. J.

E. Pickwell, B. E. Cole, A. J. Fitzgerald, and V. P. Wallace, "Simulation of terahertz pulse propagation in biological systems," Appl. Phys. Lett. 84, 2190-2192 (2004).
[CrossRef]

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

Foldy, L. L.

L. L. Foldy, "The multiple scattering of waves. I. General theory of isotropic scattering by randomly distributed scatterers" Phys. Rev. 67, 107-119 (1945).
[CrossRef]

Ford, J.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Fowler, J.

S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "2.9 THz quantum cascade laser operating at 70 K in continuous wave," Appl. Phys. Lett. 85, 1674-1676 (2004).
[CrossRef]

Garvey, D. M.

Giovannini, M.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Gladden, L. F.

Harris, G.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Harris, J. S.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Hatami, F.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Hein, G.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Hoffman, S.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Hofmann, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Hormoz, S.

Hoyler, N.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Hu, B. B.

Hu, Q.

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, "High-power quantum cascade lasers," Electron. Lett. 42, 89-90 (2006).
[CrossRef]

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

A. W. M. Lee and Q. Hu, "Real-time, continuous-wave terahertz imaging by use of a microbolometer focal-plane array," Opt. Lett. 30, 2563-2565 (2005).
[CrossRef] [PubMed]

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]

Inoue, 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]

Jian, Z.

J. Pearce, Z. Jian, and D. M. Mittleman, "Statistics of multiply scattered broadband terahertz pulses," Phys. Rev. Lett. 91, 043903-1-4 (2003).
[CrossRef] [PubMed]

Johns, M. L.

Kawase, K.

Kemp, M. C.

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[CrossRef]

Khanna, S. P.

Kim, S. M.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

King, D.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Kleine-Ostmann, T.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Knobloch, P.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Koch, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Kong, J. A.

L. Tsang and J. A. Kong, "Scattering of electromagnetic waves from a half space of densely distributed dielectric scatterers," Radio Science 18, 1260-1272 (1963).
[CrossRef]

Kubelka, P.

P. Kubelka and F. Munk, "Ein beitrag zur optic der fabanstriche," Z. Tech. Physik 12, 593-601 (1931).

Kumar, S.

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, "High-power quantum cascade lasers," Electron. Lett. 42, 89-90 (2006).
[CrossRef]

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

Kurian, A. W.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Lachab, M.

Lax, M.

M. Lax, "Multiple scattering of waves. II. The effective field in dense systems," Phys. Rev. 85, 621-629 (1952).
[CrossRef]

Lee, A. W. M.

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

A. W. M. Lee and Q. Hu, "Real-time, continuous-wave terahertz imaging by use of a microbolometer focal-plane array," Opt. Lett. 30, 2563-2565 (2005).
[CrossRef] [PubMed]

Lindberg, J. D.

Linfield, E. H.

M. A. Belkin, J. A. Fan, S. Hormoz, F. Capasso, S. P. Khanna, M. Lachab, A. G. Davies, and E. H. Linfield, "Terahertz quantum cascade lasers with copper metal-metal waveguides operating up to 178 K," Opt. Express 16, 3242-3248 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-5-3242.
[CrossRef] [PubMed]

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

K. L. Nguyen, M. L. Johns, L. F. Gladden, C. H. Worrall, P. Alexander, H. E. Beere, M. Pepper, D. A.  Ritchie, J. Alton, S. Barbieri, and E. H. Linfield, "Three-dimensional imaging with a terahertz quantum cascade laser," Opt. Express 14, 2123-2129 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-6-2123.
[CrossRef] [PubMed]

S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "2.9 THz quantum cascade laser operating at 70 K in continuous wave," Appl. Phys. Lett. 85, 1674-1676 (2004).
[CrossRef]

Liu, H-B.

Lo, T.

S. Barbieri, J. Alton, C. Baker, T. Lo, H. E. Beere, and D. Ritchie, "Imaging with THz quantum cascade lasers using a Schottky diode mixer," Opt. Express 13, 6497-6503 (2005), http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-17-6497.
[CrossRef] [PubMed]

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[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.

J. Pearce, Z. Jian, and D. M. Mittleman, "Statistics of multiply scattered broadband terahertz pulses," Phys. Rev. Lett. 91, 043903-1-4 (2003).
[CrossRef] [PubMed]

J. Pearce and D. M. Mittleman, "Propagation of single-cycle terahertz pulses in random media," Opt. Lett.  26, 2002-2004 (2001).
[CrossRef]

Morita, Y.

Munk, F.

P. Kubelka and F. Munk, "Ein beitrag zur optic der fabanstriche," Z. Tech. Physik 12, 593-601 (1931).

Munshi, T.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Nguyen, K. L.

Nuss, M. C.

O??Neil, A.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Ogawa, Y.

Oshima, Y. N.

Otani, C.

Pearce, J.

J. Pearce, Z. Jian, and D. M. Mittleman, "Statistics of multiply scattered broadband terahertz pulses," Phys. Rev. Lett. 91, 043903-1-4 (2003).
[CrossRef] [PubMed]

J. Pearce and D. M. Mittleman, "Propagation of single-cycle terahertz pulses in random media," Opt. Lett.  26, 2002-2004 (2001).
[CrossRef]

Pepper, M.

Pickwell, E.

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

E. Pickwell, B. E. Cole, A. J. Fitzgerald, and V. P. Wallace, "Simulation of terahertz pulse propagation in biological systems," Appl. Phys. Lett. 84, 2190-2192 (2004).
[CrossRef]

Pierz, K.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Pye, R. J.

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

Qin, Q.

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

Reno, J. L.

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, "High-power quantum cascade lasers," Electron. Lett. 42, 89-90 (2006).
[CrossRef]

Ritchie, D.

Ritchie, D. A.

S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "2.9 THz quantum cascade laser operating at 70 K in continuous wave," Appl. Phys. Lett. 85, 1674-1676 (2004).
[CrossRef]

Ritchie, D. A.

Sarabandi, K.

P. R. Siqueira and K. Sarabandi, "Method of moments evaluation of the two-dimensional quasi-crystalline approximation," IEEE Trans. Antenn. Prop. 44, 1067-1077 (1996).
[CrossRef]

Scalari, G.

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

Shen, Y. C.

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[CrossRef]

Siqueira, P. R.

P. R. Siqueira and K. Sarabandi, "Method of moments evaluation of the two-dimensional quasi-crystalline approximation," IEEE Trans. Antenn. Prop. 44, 1067-1077 (1996).
[CrossRef]

Smith, M. A.

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

Sperling, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

Taday, P. F.

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[CrossRef]

Tribe, R.

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[CrossRef]

Tsang, L.

L. Tsang and J. A. Kong, "Scattering of electromagnetic waves from a half space of densely distributed dielectric scatterers," Radio Science 18, 1260-1272 (1963).
[CrossRef]

Upadhya, P.

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Walker, G. C.

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

Wallace, V. P.

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

E. Pickwell, B. E. Cole, A. J. Fitzgerald, and V. P. Wallace, "Simulation of terahertz pulse propagation in biological systems," Appl. Phys. Lett. 84, 2190-2192 (2004).
[CrossRef]

Watanabe, Y.

K. Kawase, Y. Ogawa, Y. Watanabe, and H. Inoue, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Express 11, 2549-2554 (2003), http://www.opticsinfobase.org/abstract.cfm?URI=oe-11-20-2549.
[CrossRef] [PubMed]

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]

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M. S. Wertheim, "Exact solution of the Percus-Yevick integral equation for hard spheres," Phys. Rev. Lett.  10, 321-323 (1963).
[CrossRef]

Williams, B.

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, "High-power quantum cascade lasers," Electron. Lett. 42, 89-90 (2006).
[CrossRef]

Williams, B. S.

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

Woodward, R. M.

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
[CrossRef] [PubMed]

Worrall, C. H.

Yamashita, M.

Zhang, X.-C.

Zhao, H.

Zinovev, N. N.

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

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Appl. Phys. Lett. (6)

S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "2.9 THz quantum cascade laser operating at 70 K in continuous wave," Appl. Phys. Lett. 85, 1674-1676 (2004).
[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]

A. W. M. Lee, Q. Qin, S. Kumar, B. S. Williams, Q. Hu, and J. L. Reno, "Real-time terahertz imaging over a standoff distance (>25 meters)," Appl. Phys. Lett. 89, 141125-141127 (2006).
[CrossRef]

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, "Detection and identification of explosives using THz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116-241118 (2005).
[CrossRef]

S. M. Kim, F. Hatami, J. S. Harris, A. W. Kurian, J. Ford, D. King, G. Scalari, M. Giovannini, N. Hoyler, J.  Faist, and G. Harris, "Biomedical terahertz imaging with a quantum cascade laser," Appl. Phys. Lett. 88, 153903-153905 (2006).
[CrossRef]

E. Pickwell, B. E. Cole, A. J. Fitzgerald, and V. P. Wallace, "Simulation of terahertz pulse propagation in biological systems," Appl. Phys. Lett. 84, 2190-2192 (2004).
[CrossRef]

Br. J. Dermatol. (1)

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, "Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo," Br. J. Dermatol. 151, 424-432 (2004).
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Electron. Lett. (2)

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffman, M. Breede, M. Hofmann, G. Hein, K. Pierz, M.  Sperling, and K. Donhuijsen, "Continuous-wave THz imaging," Electron. Lett. 37, 1461-1463 (2001).
[CrossRef]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, "High-power quantum cascade lasers," Electron. Lett. 42, 89-90 (2006).
[CrossRef]

IEEE Trans. Antenn. Prop. (1)

P. R. Siqueira and K. Sarabandi, "Method of moments evaluation of the two-dimensional quasi-crystalline approximation," IEEE Trans. Antenn. Prop. 44, 1067-1077 (1996).
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K. L. Nguyen, M. L. Johns, L. F. Gladden, C. H. Worrall, P. Alexander, H. E. Beere, M. Pepper, D. A.  Ritchie, J. Alton, S. Barbieri, and E. H. Linfield, "Three-dimensional imaging with a terahertz quantum cascade laser," Opt. Express 14, 2123-2129 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-6-2123.
[CrossRef] [PubMed]

S. Barbieri, J. Alton, C. Baker, T. Lo, H. E. Beere, and D. Ritchie, "Imaging with THz quantum cascade lasers using a Schottky diode mixer," Opt. Express 13, 6497-6503 (2005), http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-17-6497.
[CrossRef] [PubMed]

M. A. Belkin, J. A. Fan, S. Hormoz, F. Capasso, S. P. Khanna, M. Lachab, A. G. Davies, and E. H. Linfield, "Terahertz quantum cascade lasers with copper metal-metal waveguides operating up to 178 K," Opt. Express 16, 3242-3248 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-5-3242.
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K. Kawase, Y. Ogawa, Y. Watanabe, and H. Inoue, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Express 11, 2549-2554 (2003), http://www.opticsinfobase.org/abstract.cfm?URI=oe-11-20-2549.
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Opt. Lett. (3)

Phys. Med. Biol. (1)

A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith, and J. M. Chamberlain, "An introduction to medical imaging with coherent terahertz frequency radiation," Phys. Med. Biol. 47, R67-84 (2002).
[CrossRef] [PubMed]

Phys. Rev. (2)

L. L. Foldy, "The multiple scattering of waves. I. General theory of isotropic scattering by randomly distributed scatterers" Phys. Rev. 67, 107-119 (1945).
[CrossRef]

M. Lax, "Multiple scattering of waves. II. The effective field in dense systems," Phys. Rev. 85, 621-629 (1952).
[CrossRef]

Phys. Rev. Lett. (2)

M. S. Wertheim, "Exact solution of the Percus-Yevick integral equation for hard spheres," Phys. Rev. Lett.  10, 321-323 (1963).
[CrossRef]

J. Pearce, Z. Jian, and D. M. Mittleman, "Statistics of multiply scattered broadband terahertz pulses," Phys. Rev. Lett. 91, 043903-1-4 (2003).
[CrossRef] [PubMed]

Proc. SPIE (2)

D. J. Cook, B. K. Decker, G. Dadusc, and M. G. Allen, "Through container THz sensing: applications for bio detection," in Int. Soc. Opt. Eng.Proc. SPIE 5268, 36-42 (2004).

A. Burnett, W. Fan, P. Upadhya, J. Cunningham, E. H. Linfield, A. G. Davies, H. Edwards, T. Munshi, and A. O??Neil, "Analysis of drugs of abuse and explosives using terahertz time-domain and Raman spectroscopy," Int. Soc. Opt. Eng.Proc. SPIE 6549, 61200 (2007).

Radio Science (1)

L. Tsang and J. A. Kong, "Scattering of electromagnetic waves from a half space of densely distributed dielectric scatterers," Radio Science 18, 1260-1272 (1963).
[CrossRef]

Z. Tech. Physik (1)

P. Kubelka and F. Munk, "Ein beitrag zur optic der fabanstriche," Z. Tech. Physik 12, 593-601 (1931).

Other (4)

L. Tsang, J. A. Kong, and R. T. Shin, Theory of Microwave Remote Sensing (New York, Wiley, 1985)

G. Kortum, Reflectance Spectroscopy (Springer, Berlin, 1969).

M. Naftaly, A. Malcoci, and H. Eisele, "A sensitive broadband detector for room-temperature operation of a simple terahertz Fourier-transform spectrometer," The Joint 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics, p.35 (2006).
[CrossRef]

D. Mittleman, Sensing with THz Radiation (Springer, Berlin, 2003).

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Figures (6)

Fig. 1.
Fig. 1.

Experimental apparatus for simultaneous specular (red) and diffuse (blue) imaging using a THz-frequency quantum cascade laser (QCL). D1 — room-temperature pyroelectric sensor; D2 — helium-cooled silicon bolometer.

Fig. 2.
Fig. 2.

Measurement of the modulation transfer function (MTF) of the imaging setup using vertically (blue) and horizontally (red) oriented targets. The lines are intended only to guide the eye. The 20% modulation threshold indicates spatial resolutions equal to 350 µm and 305 µm respectively.

Fig. 3.
Fig. 3.

Diffuse image of polyethylene powder enclosed inside a polythene bag and concealed behind a HDPE FedEx® envelope, taken with a 250-µm pixel size.

Fig. 4.
Fig. 4.

(a) Photograph of the sample holder (lid removed) loaded with powder admixtures. The % mass of PMMA is shown for each admixture. (b) Specular THz image of the sample shown in (a). (c) Diffuse THz image of the sample shown in (a). The non-uniform intensity distributions observed here are attributed to the presence of diffuse surface reflections and scattering from micro-cavities formed within the samples. Such effects are averaged-out with repeated measurements. All three images are displayed on the same scale. The THz images have a pixel size of 250 µm.

Fig. 5.
Fig. 5.

Measurement of the sample reflectivity R (black, right axis) as a function of volume fraction of PMMA. The corresponding values of the Kubelka-Munk remission function F(R) are also shown (red, left axis). The lines represent fits of the data to Eq. (2), in which the estimated value of γ=1.6 is used, and S=5±1 cm-1 and α1=42±11 cm-1are treated as free parameters.

Fig. 6.
Fig. 6.

Measurement of the backscattering cross-section as a function of volume fraction of PMMA under the (a) EFA (black), (b) QCA-PY (blue) and QCA-CP (red; data points not shown).

Equations (2)

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F ( R ) = ( 1 R ) 2 2 R = K S .
F ( R ) 3 2 n 2 S [ c α 1 + ( 1 c ) α 2 ] .

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