Abstract

An imaging system in reflection geometry based on a multimode 2.9 THz quantum cascade laser as radiation source is reported. The beating between neighbouring longitudinal modes is detected using a room temperature point-contact Schottky diode as mixing element. We show that the technique can, in principle, give a dynamic range of 60 dB with a time constant of ~ 10 μs.

© 2005 Optical Society of America

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References

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  1. C. Baker, W. R. Tribe, B. E. Cole, and M. C. Kemp, �??Developments in people screening using THz technology,�?? Proc. SPIE Int. Soc. Opt. Eng. 5616, 61 (2004)
  2. Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, W. R. Tribe, and M. C. Kemp, �??Detection and identification of explosives using THz pulsed spectroscopic imaging,�?? Appl. Phys. Lett. 86, 241116 (2005)
    [CrossRef]
  3. S. Wang, B. Ferguson, D. Abbot, and X.-C Zhang, �??T-ray imaging and tomography,�?? J. Biol. Phys. 29, 247 (2003)
    [CrossRef]
  4. See, for example, D. Mittleman, Sensing with THz radiation (Springer, Berlin, 2003)
  5. B. B. Hu, and M. C. Nuss, �??Imaging with THz waves,�?? Opt. Lett. 20, 1716 (1995)
    [CrossRef] [PubMed]
  6. V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, �??Terahertz pulsed imaging of cancers,�?? Appl. Phys. Lett. 84, 2190 (2004)
  7. 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 (2004)
    [CrossRef]
  8. A. J. Fitzgerald, B. E. Cole, and P. F. Taday, �??Nondestructive analysis of tablet coating thicknesses using THz pulsed imaging,�?? J. Pharm. Sciences 94, 177 (2005)
    [CrossRef]
  9. N. Karpowicz, H. Zhong, C. Zhang, K.-I Lin, J-S. Hwang, J. Xu, and X.-C. Zhang, �??Compact continuous-wave subterahertz system for inspection applications,�?? Appl. Phys. Lett. 86, 054105 (2005)
    [CrossRef]
  10. W. R Tribe, D. A. Newnham, P. F. Taday, and M. C. Kemp, �??Hidden object detection: security applications of THz technology,�?? Proc. SPIE Int. Soc. Opt. Eng. 5434, 168 (2004)
  11. A. Maestrini, J. Ward, J. Gill, H. Javadi, E. Schlecht, G. Chattopadhyay, F. Maiwald, N. R. Erickson, and I. Mehdi, �??A 1.7 �?? 1.9 local oscillator source,�?? IEEE Microwave and Wireless Comp. Lett 14, 253 (2004)
    [CrossRef]
  12. 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, 156 (2002)
    [CrossRef] [PubMed]
  13. S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, �??2.9 THz quantum cascade laser operating up to 70K in continuous wave,�?? Appl. Phys. Lett. 85, 1674 (2004)
    [CrossRef]
  14. L. Ajili, G. Scalari, J. Faist, H. E. Beere, E. H. Linfield, D. A. Ritchie, and A. G. Davies, �??High power quantum cascade lasers operating at λ= 87 and 130 μm,�?? Appl. Phys. Lett. 85, 3986 (2004)
    [CrossRef]
  15. B. S. Williams, S. Kumar, and Q. Hu, �??Operation of THz Quantum cascade lasers at 164K in pulsed mode and at 117K in continuous-wave mode,�?? Opt. Express 13, 3331 (2005)
    [CrossRef] [PubMed]
  16. C. Worral, J. Alton, M. Houghton, S. Barbieri, C. Sirtori, H. E. Beere, and D. A. Ritchie, �??High power superlatticel quantum cascade laser emitting at 2 THz,�?? unpublished (June 2005)
  17. Operation at 1.39THz has been achieved with a QCL subject to a magnetic field of 6T. Jerome Faist, private communication.
  18. J. Darmo, V. Tamosiunas, G. Fasching, J. Kröll, K. Unterrainer, M. Beck, M. Giovannini, J. Faist, C. Kremser, and P. Debbage, �??Imaging with a THz quantum cascade laser,�?? Opt. Expr. 12, 1879 (2004)
    [CrossRef]
  19. D. R. Chamberlin, P. R. Robrish, W. R. Trutna, G. Scalari, M. Giovannini, L. Ajili, and J. Faist, �??Dual wavelength THz imaging with quantum cascade lasers,�?? Appl. Opt. 44, 121 (2005)
    [CrossRef] [PubMed]
  20. A. Barkan, F. K. Tittel, D. M. Mittleman, R. Dengler, P. H. Siegel, G. Scalari, L. Ajili, F. Faist, H. E. Beere, E. H. Linfield, D. A. Ritchie, and A. G. Davies, �??Linewidth and tuning characteristics of THz quantum cascade lasers,�?? Opt. Lett. 29, 575 (2004).
    [CrossRef] [PubMed]
  21. S. Barbieri, J. Alton, H. E. Beere, H. Linfield, D. A. Ritchie, S. Withington, G. Scalari, L. Ajili, and J. Faist, �??Heterodyne mixing of two far-infrared quantum cascade lasers by use of a point-contact Schottky diode,�?? Opt. Lett. 29, 1633 (2004)
    [CrossRef]
  22. A.L. Betz, R.T. Boreiko, B. S. Williams, S. Kumar, Q. Hu, and J. L. Reno, �??Frequency and phase-lock control of a 3 THz quantum cascade laser,�?? Opt. Lett. 30, 1837 (2005)
    [CrossRef] [PubMed]
  23. A similar behaviour was found in mid-IR QCLs by measuring the beating between neighbouring Fabry-Perot modes with a fast quantum well photodetector. See A. Soibel, F. Capasso, C. Gmachl, M. L. Peabody, A. M. Serget, R. Paiella, D. L. Sivco, A. Y. Cho, and H. C. Liu, �??Stability of pulsed emission and enhancement of intracavity second-harmonic generation in self mode-locked quantum cascade lasers,�?? IEEE J. Quantum. Electron 40, 197 (2004)
    [CrossRef]
  24. The 35 dBm residual dynamic range results from resolution bandwidth of 100 kHz used in the experiment, yielding a dynamic range of 70 dBm.
  25. G. Narayanan, N. R. Erickson, and A. W. Lichtenberger, �??Development of multi-pixel heterodyne array instruments at submillimeter wavelengths,�?? Proc. Far-IR, Sub-MM, and MM Detector Technology Workshop, 203 (2002)

Appl. Opt.

Appl. Phys. Lett.

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

L. Ajili, G. Scalari, J. Faist, H. E. Beere, E. H. Linfield, D. A. Ritchie, and A. G. Davies, �??High power quantum cascade lasers operating at λ= 87 and 130 μm,�?? Appl. Phys. Lett. 85, 3986 (2004)
[CrossRef]

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

V. P. Wallace, R. M. Woodward, A. J. Fitzgerald, E. Pickwell, R. J. Pye, and D. D. Arnone, �??Terahertz pulsed imaging of cancers,�?? Appl. Phys. Lett. 84, 2190 (2004)

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 (2004)
[CrossRef]

N. Karpowicz, H. Zhong, C. Zhang, K.-I Lin, J-S. Hwang, J. Xu, and X.-C. Zhang, �??Compact continuous-wave subterahertz system for inspection applications,�?? Appl. Phys. Lett. 86, 054105 (2005)
[CrossRef]

Far-IR, Sub-MM, & MM Detector Tech '02

G. Narayanan, N. R. Erickson, and A. W. Lichtenberger, �??Development of multi-pixel heterodyne array instruments at submillimeter wavelengths,�?? Proc. Far-IR, Sub-MM, and MM Detector Technology Workshop, 203 (2002)

IEEE J. Quantum. Electron

A similar behaviour was found in mid-IR QCLs by measuring the beating between neighbouring Fabry-Perot modes with a fast quantum well photodetector. See A. Soibel, F. Capasso, C. Gmachl, M. L. Peabody, A. M. Serget, R. Paiella, D. L. Sivco, A. Y. Cho, and H. C. Liu, �??Stability of pulsed emission and enhancement of intracavity second-harmonic generation in self mode-locked quantum cascade lasers,�?? IEEE J. Quantum. Electron 40, 197 (2004)
[CrossRef]

IEEE Microwave and Wireless Comp. Lett

A. Maestrini, J. Ward, J. Gill, H. Javadi, E. Schlecht, G. Chattopadhyay, F. Maiwald, N. R. Erickson, and I. Mehdi, �??A 1.7 �?? 1.9 local oscillator source,�?? IEEE Microwave and Wireless Comp. Lett 14, 253 (2004)
[CrossRef]

J. Biol. Phys.

S. Wang, B. Ferguson, D. Abbot, and X.-C Zhang, �??T-ray imaging and tomography,�?? J. Biol. Phys. 29, 247 (2003)
[CrossRef]

J. Pharm. Sciences

A. J. Fitzgerald, B. E. Cole, and P. F. Taday, �??Nondestructive analysis of tablet coating thicknesses using THz pulsed imaging,�?? J. Pharm. Sciences 94, 177 (2005)
[CrossRef]

Nature

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, 156 (2002)
[CrossRef] [PubMed]

Opt. Expr.

J. Darmo, V. Tamosiunas, G. Fasching, J. Kröll, K. Unterrainer, M. Beck, M. Giovannini, J. Faist, C. Kremser, and P. Debbage, �??Imaging with a THz quantum cascade laser,�?? Opt. Expr. 12, 1879 (2004)
[CrossRef]

Opt. Express

Opt. Lett.

Proc. SPIE

C. Baker, W. R. Tribe, B. E. Cole, and M. C. Kemp, �??Developments in people screening using THz technology,�?? Proc. SPIE Int. Soc. Opt. Eng. 5616, 61 (2004)

Proc. SPIE Int. Soc. Opt. Eng.

W. R Tribe, D. A. Newnham, P. F. Taday, and M. C. Kemp, �??Hidden object detection: security applications of THz technology,�?? Proc. SPIE Int. Soc. Opt. Eng. 5434, 168 (2004)

Other

See, for example, D. Mittleman, Sensing with THz radiation (Springer, Berlin, 2003)

C. Worral, J. Alton, M. Houghton, S. Barbieri, C. Sirtori, H. E. Beere, and D. A. Ritchie, �??High power superlatticel quantum cascade laser emitting at 2 THz,�?? unpublished (June 2005)

Operation at 1.39THz has been achieved with a QCL subject to a magnetic field of 6T. Jerome Faist, private communication.

The 35 dBm residual dynamic range results from resolution bandwidth of 100 kHz used in the experiment, yielding a dynamic range of 70 dBm.

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Figures (3)

Fig. 1.
Fig. 1.

Layout of the experimental apparatus. Laser emission and IF signal spectra are also represented schematically. The separation of ~13 GHz between neighbouring longitudinal Fabry-Perot modes corresponds to a QCL cavity length of 3mm.

Fig 2.
Fig 2.

IF power spectrum detected at the output of the SDM with two different resolution bandwidths of the spectrum analyser. The QCL was driven in CW with a current of 1.4 A at T = 10K. The IF signal was amplified with a two-stage, 50 dB gain, 12–14 GHz low noise preamplifier (MITEQ, JSD3 and JSD2 series). Inset: QCL emission spectrum recorded with a Fourier transform infrared spectrometer (0.25 cm-1 resolution).

Fig 3.
Fig 3.

Examples of THz images. Left: Image of a gold pattern evaporated on top of a TPX window (100 μm2 pixels). Right: A razor blade imaged through a standard A4 paper sheet (200 μm2 pixels). Regions of different colours correspond to different intensities detected by the mixer as a consequence of the blade surface not being perfectly flat (see text). The light concentric rings visible on the image are produced by rings patterned on the surface of the circular 1mm thick polythene spacer placed between the blade and the paper. Additional non-uniformity of the horizontal edges of the blade (see for instance the bottom edge) is due to the translation stage not regaining exactly the same position in subsequent vertical scans.

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