Abstract

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.

© 2009 OSA

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    [CrossRef]

2009 (1)

S. Kumar, Q. Hu, and J. L. Reno, “186 K operation of terahertz quantum-cascade lasers based on a diagonal design,” Appl. Phys. Lett. 94(13), 131105–131107 (2009).
[CrossRef]

2008 (4)

2007 (4)

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(19), 12060–12067 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-19-12060 .
[CrossRef] [PubMed]

J. R. Fletcher, G. P. Swift, D. C. Dai, J. A. Levitt, and J. M. Chamberlain, “Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation,” J. Appl. Phys. 101(1), 013102 (2007).
[CrossRef]

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[CrossRef]

2006 (6)

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(14), 141125–141127 (2006).
[CrossRef]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, “High-power terahertz quantum-cascade lasers,” Electron. Lett. 42(2), 89–90 (2006).
[CrossRef]

A. W. M. Lee, B. S. Wil, S. Kumar, Qing Hu, and J. L. Reno, “Real-time imaging using a 4.3-THz quantum cascade laser and a 320 x 240 microbolometer focal-plane array,” IEEE Photon. Technol. Lett. 18(13), 1415–1417 (2006).
[CrossRef]

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (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(15), 153903–153905 (2006).
[CrossRef]

H. Zhong, A. Redo-Sanchez, and X.-C. Zhang, “Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system,” Opt. Express 14(20), 9130–9141 (2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-20-9130 .
[CrossRef] [PubMed]

2005 (3)

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, “Detection and identification of explosives using terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

2004 (2)

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

A. Dobroiu, M. Yamashita, Y. N. Ohshima, Y. Morita, C. Otani, and K. Kawase, “Terahertz imaging system based on a backward-wave oscillator,” Appl. Opt. 43(30), 5637–5646 (2004).
[CrossRef] [PubMed]

2003 (2)

K. Kawase, Y. Ogawa, Y. Watanabe, and H. Inoue, “Non-destructive terahertz imaging of illicit drugs using spectral fingerprints,” Opt. Express 11(20), 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(4), 800–802 (2003).
[CrossRef]

2002 (2)

S. Mair, B. Gompf, and M. Dressel, “Microspectroscopy and imaging in the THz range using coherent CW radiation,” Phys. Med. Biol. 47(21), 3719–3725 (2002).
[CrossRef] [PubMed]

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

2001 (1)

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

1995 (1)

1949 (1)

C. V. Raman, “The theory of the Christiansen experiment,” Proc. Indian. Acad. Sci, Sect. A 29, 381–389 (1949).

Aers, G. C.

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

Arnone, D. D.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

Bastiaans, G. J.

Beere, H. E.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

Belkin, M. A.

Beltram, F.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

Breede, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Burnett, A.

Cao, J. C.

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

Capasso, F.

Chakraborty, S.

Chamberlain, J. M.

J. R. Fletcher, G. P. Swift, D. C. Dai, J. A. Levitt, and J. M. Chamberlain, “Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation,” J. Appl. Phys. 101(1), 013102 (2007).
[CrossRef]

Chen, J.

Chen, Y.

Cluff, J.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

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 terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

Dai, D. C.

J. R. Fletcher, G. P. Swift, D. C. Dai, J. A. Levitt, and J. M. Chamberlain, “Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation,” J. Appl. Phys. 101(1), 013102 (2007).
[CrossRef]

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(5), 3242–3248 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-5-3242 .
[CrossRef] [PubMed]

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

S. P. Khanna, M. Salih, P. Dean, A. G. Davies, and E. H. Linfield, “Electrically tunable terahertz quantum cascade laser with a heterogeneous active region,” Appl. Phys. Lett. in press.

Davies, G.

Dean, P.

Dobroiu, A.

Donhuijsen, K.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Dressel, M.

S. Mair, B. Gompf, and M. Dressel, “Microspectroscopy and imaging in the THz range using coherent CW radiation,” Phys. Med. Biol. 47(21), 3719–3725 (2002).
[CrossRef] [PubMed]

Faist, J.

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[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(15), 153903–153905 (2006).
[CrossRef]

Fan, J. A.

Fischer, B. M.

M. Franz, B. M. Fischer, and M. Walther, “The Christiansen effect in terahertz time-domain spectra of coarse-grained powders,” Appl. Phys. Lett. 92(2), 021107 (2008).
[CrossRef]

Fischer, M.

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[CrossRef]

Fitzgerald, A. J.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

Flanagan, N.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

Fletcher, J. R.

J. R. Fletcher, G. P. Swift, D. C. Dai, J. A. Levitt, and J. M. Chamberlain, “Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation,” J. Appl. Phys. 101(1), 013102 (2007).
[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(15), 153903–153905 (2006).
[CrossRef]

Franz, M.

M. Franz, B. M. Fischer, and M. Walther, “The Christiansen effect in terahertz time-domain spectra of coarse-grained powders,” Appl. Phys. Lett. 92(2), 021107 (2008).
[CrossRef]

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(15), 153903–153905 (2006).
[CrossRef]

Gompf, B.

S. Mair, B. Gompf, and M. Dressel, “Microspectroscopy and imaging in the THz range using coherent CW radiation,” Phys. Med. Biol. 47(21), 3719–3725 (2002).
[CrossRef] [PubMed]

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(15), 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(15), 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(15), 153903–153905 (2006).
[CrossRef]

Hein, G.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Hoffmann, S.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Hofmann, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Hormoz, S.

Hoyler, N.

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[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(15), 153903–153905 (2006).
[CrossRef]

Hu, B. B.

Hu, Q.

S. Kumar, Q. Hu, and J. L. Reno, “186 K operation of terahertz quantum-cascade lasers based on a diagonal design,” Appl. Phys. Lett. 94(13), 131105–131107 (2009).
[CrossRef]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, “High-power terahertz quantum-cascade lasers,” Electron. Lett. 42(2), 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(14), 141125–141127 (2006).
[CrossRef]

Hwang, J.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

Hwang, J. S.

N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

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(4), 800–802 (2003).
[CrossRef]

Inoue, H.

Iotti, R. C.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

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(4), 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(4), 800–802 (2003).
[CrossRef]

Karpowicz, N.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

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 terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 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(15), 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(15), 153903–153905 (2006).
[CrossRef]

Kleine-Ostmann, T.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Knobloch, P.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Koch, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Köhler, R.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

Kumar, S.

S. Kumar, Q. Hu, and J. L. Reno, “186 K operation of terahertz quantum-cascade lasers based on a diagonal design,” Appl. Phys. Lett. 94(13), 131105–131107 (2009).
[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(14), 141125–141127 (2006).
[CrossRef]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, “High-power terahertz quantum-cascade lasers,” Electron. Lett. 42(2), 89–90 (2006).
[CrossRef]

A. W. M. Lee, B. S. Wil, S. Kumar, Qing Hu, and J. L. Reno, “Real-time imaging using a 4.3-THz quantum cascade laser and a 320 x 240 microbolometer focal-plane array,” IEEE Photon. Technol. Lett. 18(13), 1415–1417 (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(15), 153903–153905 (2006).
[CrossRef]

Lachab, M.

Laframboise, S. R.

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

Lee, A. W. M.

A. W. M. Lee, B. S. Wil, S. Kumar, Qing Hu, and J. L. Reno, “Real-time imaging using a 4.3-THz quantum cascade laser and a 320 x 240 microbolometer focal-plane array,” IEEE Photon. Technol. Lett. 18(13), 1415–1417 (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(14), 141125–141127 (2006).
[CrossRef]

Levitt, J. A.

J. R. Fletcher, G. P. Swift, D. C. Dai, J. A. Levitt, and J. M. Chamberlain, “Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation,” J. Appl. Phys. 101(1), 013102 (2007).
[CrossRef]

Li, N.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

Liang, L.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

Lin, K.

N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

Linfield, E. H.

Liu, H. C.

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

Lo, T.

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, “Detection and identification of explosives using terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

Lu, M.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

Luo, H.

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
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S. Mair, B. Gompf, and M. Dressel, “Microspectroscopy and imaging in the THz range using coherent CW radiation,” Phys. Med. Biol. 47(21), 3719–3725 (2002).
[CrossRef] [PubMed]

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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(4), 800–802 (2003).
[CrossRef]

Morita, Y.

Nuss, M. C.

Ogawa, Y.

Ohshima, Y. N.

Otani, C.

Pepper, M.

Y. C. Shen, P. F. Taday, and M. Pepper, “Elimination of scattering effects in soectral measurement of granulated materials using terahertz pulsed spectroscopy,” Appl. Phys. Lett. 92(5), 051103–051105 (2008).
[CrossRef]

Pierz, K.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Pye, R. J.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 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(14), 141125–141127 (2006).
[CrossRef]

Qing Hu,

A. W. M. Lee, B. S. Wil, S. Kumar, Qing Hu, and J. L. Reno, “Real-time imaging using a 4.3-THz quantum cascade laser and a 320 x 240 microbolometer focal-plane array,” IEEE Photon. Technol. Lett. 18(13), 1415–1417 (2006).
[CrossRef]

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C. V. Raman, “The theory of the Christiansen experiment,” Proc. Indian. Acad. Sci, Sect. A 29, 381–389 (1949).

Redo-Sanchez, A.

Reno, J. L.

S. Kumar, Q. Hu, and J. L. Reno, “186 K operation of terahertz quantum-cascade lasers based on a diagonal design,” Appl. Phys. Lett. 94(13), 131105–131107 (2009).
[CrossRef]

A. W. M. Lee, B. S. Wil, S. Kumar, Qing Hu, and J. L. Reno, “Real-time imaging using a 4.3-THz quantum cascade laser and a 320 x 240 microbolometer focal-plane array,” IEEE Photon. Technol. Lett. 18(13), 1415–1417 (2006).
[CrossRef]

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, “High-power terahertz quantum-cascade lasers,” Electron. Lett. 42(2), 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(14), 141125–141127 (2006).
[CrossRef]

Ritchie, D. A.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

Rossi, F.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

Salih, M.

S. P. Khanna, M. Salih, P. Dean, A. G. Davies, and E. H. Linfield, “Electrically tunable terahertz quantum cascade laser with a heterogeneous active region,” Appl. Phys. Lett. in press.

Scalari, G.

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[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(15), 153903–153905 (2006).
[CrossRef]

Shankar, S.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

Shaukat, M. U.

Shen, J.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

Shen, Y. C.

Y. C. Shen, P. F. Taday, and M. Pepper, “Elimination of scattering effects in soectral measurement of granulated materials using terahertz pulsed spectroscopy,” Appl. Phys. Lett. 92(5), 051103–051105 (2008).
[CrossRef]

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, “Detection and identification of explosives using terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

Sperling, M.

T. Kleine-Ostmann, P. Knobloch, M. Koch, S. Hoffmann, M. Breede, M. Hofmann, G. Hein, K. Pierz, M. Sperling, and K. Donhuijsen, “Continuous-wave THz imaging,” Electron. Lett. 37(24), 1461–1462 (2001).
[CrossRef]

Swift, G. P.

J. R. Fletcher, G. P. Swift, D. C. Dai, J. A. Levitt, and J. M. Chamberlain, “Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation,” J. Appl. Phys. 101(1), 013102 (2007).
[CrossRef]

Taday, P. F.

Y. C. Shen, P. F. Taday, and M. Pepper, “Elimination of scattering effects in soectral measurement of granulated materials using terahertz pulsed spectroscopy,” Appl. Phys. Lett. 92(5), 051103–051105 (2008).
[CrossRef]

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, R. Tribe, and M. C. Kemp, “Detection and identification of explosives using terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

Terazzi, R.

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[CrossRef]

Tredicucci, A.

R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, “Terahertz semiconductor-heterostructure laser,” Nature 417(6885), 156–159 (2002).
[CrossRef] [PubMed]

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 terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

Wallace, V. P.

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
[CrossRef] [PubMed]

Walther, C.

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[CrossRef]

Walther, M.

M. Franz, B. M. Fischer, and M. Walther, “The Christiansen effect in terahertz time-domain spectra of coarse-grained powders,” Appl. Phys. Lett. 92(2), 021107 (2008).
[CrossRef]

Wasilewski, Z. R.

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

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(4), 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(20), 2549–2554 (2003), http://www.opticsinfobase.org/abstract.cfm?URI=oe-11-20-2549 .
[CrossRef] [PubMed]

Wil, B. S.

A. W. M. Lee, B. S. Wil, S. Kumar, Qing Hu, and J. L. Reno, “Real-time imaging using a 4.3-THz quantum cascade laser and a 320 x 240 microbolometer focal-plane array,” IEEE Photon. Technol. Lett. 18(13), 1415–1417 (2006).
[CrossRef]

Williams, B.

B. Williams, S. Kumar, Q. Hu, and J. L. Reno, “High-power terahertz quantum-cascade lasers,” Electron. Lett. 42(2), 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(14), 141125–141127 (2006).
[CrossRef]

Xu, J.

N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

Xu, X.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

Yamashita, M.

Zhang, C.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
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Zhang, X.-C.

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(19), 12060–12067 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-19-12060 .
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H. Zhong, A. Redo-Sanchez, and X.-C. Zhang, “Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system,” Opt. Express 14(20), 9130–9141 (2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-20-9130 .
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N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

Zhang, Y.

M. Lu, J. Shen, N. Li, Y. Zhang, C. Zhang, L. Liang, and X. Xu, “Detection and identification of illicit drugs using terahertz imaging,” J. Appl. Phys. 100(10), 103104–103106 (2006).
[CrossRef]

Zhao, H.

Zhong, H.

H. Zhong, A. Redo-Sanchez, and X.-C. Zhang, “Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system,” Opt. Express 14(20), 9130–9141 (2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-20-9130 .
[CrossRef] [PubMed]

N. Karpowicz, H. Zhong, J. Xu, K. Lin, J. S. Hwang, and X.-C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20(7), S293–S299 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

Appl. Opt. (1)

Appl. Phys. Lett. (11)

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(4), 800–802 (2003).
[CrossRef]

S. P. Khanna, M. Salih, P. Dean, A. G. Davies, and E. H. Linfield, “Electrically tunable terahertz quantum cascade laser with a heterogeneous active region,” Appl. Phys. Lett. in press.

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(15), 153903–153905 (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 terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86(24), 241116–241118 (2005).
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. Hwang, J. Xu, and X.-C. Zhang, “Compact continuous-wave subterahertz system for inspection applications,” Appl. Phys. Lett. 86(5), 054105–054107 (2005).
[CrossRef]

C. Walther, M. Fischer, G. Scalari, R. Terazzi, N. Hoyler, and J. Faist, “Quantum cascade lasers operating from 1.2 to 1.6 THz,” Appl. Phys. Lett. 91(13), 131122 (2007).
[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(14), 141125–141127 (2006).
[CrossRef]

S. Kumar, Q. Hu, and J. L. Reno, “186 K operation of terahertz quantum-cascade lasers based on a diagonal design,” Appl. Phys. Lett. 94(13), 131105–131107 (2009).
[CrossRef]

H. Luo, S. R. Laframboise, Z. R. Wasilewski, G. C. Aers, H. C. Liu, and J. C. Cao, “Terahertz quantum-cascade lasers based on a three-well active module,” Appl. Phys. Lett. 90(4), 041112 (2007).
[CrossRef]

Y. C. Shen, P. F. Taday, and M. Pepper, “Elimination of scattering effects in soectral measurement of granulated materials using terahertz pulsed spectroscopy,” Appl. Phys. Lett. 92(5), 051103–051105 (2008).
[CrossRef]

M. Franz, B. M. Fischer, and M. Walther, “The Christiansen effect in terahertz time-domain spectra of coarse-grained powders,” Appl. Phys. Lett. 92(2), 021107 (2008).
[CrossRef]

Br. J. Dermatol. (1)

V. P. Wallace, A. J. Fitzgerald, S. Shankar, N. Flanagan, R. J. Pye, J. Cluff, and D. D. Arnone, “Terahertz pulsed imaging of basal cell carcinoma ex vivo and in vivo,” Br. J. Dermatol. 151(2), 424–432 (2004).
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Electron. Lett. (2)

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Figures (7)

Fig. 1
Fig. 1

Current-voltage (blue, left axis) and light-current (black, right axis) characteristics of the QCL used for this study, driven by 2 µs pulses at a repetition rate of 10 kHz and a temperature of 15 K. The dimensions of the QCL are 2.1 mm x 140 µm x 10 µm. Inset: Emission spectra obtained at peak driving biases of 14.2 V (blue) and 16.2 V (red).

Fig. 2
Fig. 2

Experimental apparatus used for dual-frequency imaging with a quantum cascade laser. The arrows indicate two-dimensional raster scanning.

Fig. 3
Fig. 3

Transmission images of a pellet containing 26-vol % PETN taken at (a) 3.05 THz and (b) 3.24 THz. Both images are normalised to the incident power. Difference transmission T 3.24T 3.05 image of (c) the PETN pellet and (d) a pure lactose monohydrate pellet. Images (a) and (b), and (c) and (d), are shown on the same colour scales.

Fig. 4
Fig. 4

Attenuation spectra of pellets containing (a) 26-vol % PETN (green), lactose monohydrate (black), glucose monohydrate (blue) and sucrose (red), obtained using terahertz time-domain spectroscopy in a purged environment. The spectral resolution is ~150 GHz; 4-times zero-padding has been applied. The QCL imaging frequencies are indicated by the vertical black lines.

Fig. 5
Fig. 5

Difference-attenuation [ln(T 3.24) – ln(T 3.05)] image of pellets of (a) 26-vol % PETN, (b) pure lactose monohydrate, (c) pure glucose monohydrate and (d) pure sucrose. Image (a) has been multiplied by a factor of ten for clarity.

Fig. 6
Fig. 6

Difference-attenuation coefficients Δβ = (β 3.05β 3.24) measured for samples of PETN (green), lactose monohydrate (black), glucose monohydrate (blue) and sucrose (red), diluted with PTFE. The solid lines are least-squares fits to Eq. (2). The data for lactose monohydrate has been divided by 5 for clarity.

Fig. 7
Fig. 7

Difference-intensity I 3.24I 3.05 transmission images of pellets containing (a) 26-vol % PETN and (b) pure lactose monohydrate, obtained at an amplitude modulation frequency of 10 Hz. Both images have been normalised to the difference-intensity measured for the PETN pellet. Image (b) has been multiplied by a factor of ten for clarity.

Equations (2)

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T = ( 1 R ) 2 exp ( β L ) ,
β = α 0 c + 4 μ 0 c ( 1 c ) .

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