Abstract

We demonstrate quasi-optical, diffraction-limited two-dimensional image production by means of reflected pulses of terahertz (THz) radiation. A spherical mirror is used to form a real one-to-one THz image of two 1-mm-diameter steel spheres, which is then scanned over a THz receiver. Diffraction-limited spatial (cross-range) resolution and THz pulse range resolution are simultaneously observed.

© 2001 Optical Society of America

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References

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  1. B. B. Hu and M. C. Nuss, Opt. Lett. 20, 1716 (1995).
    [CrossRef]
  2. D. M. Mittleman, S. Hunsche, L. Boivin, and M. C. Nuss, Opt. Lett. 22, 904 (1997).
    [CrossRef] [PubMed]
  3. Q. Wu, T. D. Hewitt, and X.-C. Zhang, Appl. Phys. Lett. 69, 1026 (1996).
    [CrossRef]
  4. Z. Jiang and X.-C. Zhang, Opt. Lett. 23, 1114 (1998).
    [CrossRef]
  5. D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
    [CrossRef]
  6. R. A. Cheville and D. Grischkowsky, Appl. Phys. Lett. 67, 1960 (1995).
    [CrossRef]
  7. M. van Exter and D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
    [CrossRef]
  8. F. Ulaby, Fundamentals of Applied Electromagnetics (Prentice-Hall, Englewood Cliffs, N.J., 1997), Sec.  10-5.3.
  9. M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge U. Press, Cambridge, 1999), Secs.  8.8.1 and 8.8.2.
    [CrossRef]

1999 (1)

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

1998 (1)

1997 (1)

1996 (1)

Q. Wu, T. D. Hewitt, and X.-C. Zhang, Appl. Phys. Lett. 69, 1026 (1996).
[CrossRef]

1995 (2)

B. B. Hu and M. C. Nuss, Opt. Lett. 20, 1716 (1995).
[CrossRef]

R. A. Cheville and D. Grischkowsky, Appl. Phys. Lett. 67, 1960 (1995).
[CrossRef]

1990 (1)

M. van Exter and D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

Baraniuk, R.

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Boivin, L.

Born, M.

M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge U. Press, Cambridge, 1999), Secs.  8.8.1 and 8.8.2.
[CrossRef]

Cheville, R. A.

R. A. Cheville and D. Grischkowsky, Appl. Phys. Lett. 67, 1960 (1995).
[CrossRef]

Grischkowsky, D.

R. A. Cheville and D. Grischkowsky, Appl. Phys. Lett. 67, 1960 (1995).
[CrossRef]

M. van Exter and D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

Gupta, M.

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Hewitt, T. D.

Q. Wu, T. D. Hewitt, and X.-C. Zhang, Appl. Phys. Lett. 69, 1026 (1996).
[CrossRef]

Hu, B. B.

Hunsche, S.

Jiang, Z.

Koch, M.

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Mittleman, D.

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Mittleman, D. M.

Neelamani, R.

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Nuss, M. C.

Rudd, J.

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Ulaby, F.

F. Ulaby, Fundamentals of Applied Electromagnetics (Prentice-Hall, Englewood Cliffs, N.J., 1997), Sec.  10-5.3.

van Exter, M.

M. van Exter and D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

Wolf, E.

M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge U. Press, Cambridge, 1999), Secs.  8.8.1 and 8.8.2.
[CrossRef]

Wu, Q.

Q. Wu, T. D. Hewitt, and X.-C. Zhang, Appl. Phys. Lett. 69, 1026 (1996).
[CrossRef]

Zhang, X.-C.

Z. Jiang and X.-C. Zhang, Opt. Lett. 23, 1114 (1998).
[CrossRef]

Q. Wu, T. D. Hewitt, and X.-C. Zhang, Appl. Phys. Lett. 69, 1026 (1996).
[CrossRef]

Appl. Phys. B (1)

D. Mittleman, M. Gupta, R. Neelamani, R. Baraniuk, J. Rudd, and M. Koch, Appl. Phys. B 68, 1085 (1999).
[CrossRef]

Appl. Phys. Lett. (2)

R. A. Cheville and D. Grischkowsky, Appl. Phys. Lett. 67, 1960 (1995).
[CrossRef]

Q. Wu, T. D. Hewitt, and X.-C. Zhang, Appl. Phys. Lett. 69, 1026 (1996).
[CrossRef]

IEEE Trans. Microwave Theory Tech. (1)

M. van Exter and D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

Opt. Lett. (3)

Other (2)

F. Ulaby, Fundamentals of Applied Electromagnetics (Prentice-Hall, Englewood Cliffs, N.J., 1997), Sec.  10-5.3.

M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge U. Press, Cambridge, 1999), Secs.  8.8.1 and 8.8.2.
[CrossRef]

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Figures (5)

Fig. 1
Fig. 1

Quasi-optic THz imaging system. The object, two 1-mm-diameter steel spheres, is placed on a stealth-shaped paraffin holder for invisibility. It is translated in the x direction by a motorized translation stage. The system’s optic axis is defined by the dashed–dotted lines.

Fig. 2
Fig. 2

Single time-domain measurement, Et,2.4 mm, with its normalized amplitude spectrum shown in the inset. The arrows indicate the pulse width, τ=540 fs, used for finding the range resolution. The horizontal scale of the spectrum is in units of THz.

Fig. 3
Fig. 3

Two-dimensional image of the object. The image is a composition of 61 individual time-domain measurements represented by contours, each corresponding to a constant value in x. The image shows one temporal and one spatial dimension. We have given two scales for the z axis to show the direct translation of time (in picoseconds) into space (in millimeters). The triangles indicate the location of the individual time-domain measurement, Et,2.4 mm, shown in Fig.  2.

Fig. 4
Fig. 4

Contour plan view of Fig.  3. The separation between the spheres is given in both the x and the z directions. The peak amplitude of the image is normalized to unity, and contour lines represent 0.25 steps; therefore contours at 0.50 are the half-maximum contours. Small dots mark the locations of the two peaks. Normalized peak amplitudes are 1 and 0.98 for the left and right peaks, respectively. Zero contours are labeled for reference. Negative contours are shown as dashed curves. The triangles indicate the location of the individual time-domain measurement, Et,2.4 mm, shown in Fig.  2.

Fig. 5
Fig. 5

Direct comparison of theoretical and experimental spatial resolution. The thick curve is the calculated, diffraction-limited spatial amplitude pattern. It is plotted against the two-dimensional image viewed in the z direction. For clarification, the two-dimensional image is plotted as a composition of contours that are constant in z, unlike in Fig.  3 where contours are constant in x. With this view, image features that occur earlier in time obstruct image features that occur later in time. Later features are visible only when their magnitudes exceed those of the earlier features. This view also reveals some of the negative signal data, which, as expected, show the same diffraction effects as the positive signal data. The FWHM of the calculated pattern, 1.79  mm, is indicated by the arrows.

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