Abstract

Spatially shaped femtosecond laser pulses are used to generate and to focus tunable terahertz (THz) pulses by Optical Rectification in a Zinc Telluride (ZnTe) crystal. It is shown analytically and experimentally that the focusing position and spectrum of the emitted THz pulse can be changed, in the intermediate field zone, by controlling the spatial shape of the near-infrared (NIR) femtosecond (fs) laser pump. In particular, if the pump consists of concentric circles, the emitted THz radiation is confined around the propagation axis, producing a THz pulse train, and focusing position and spectrum can be controlled by changing the number of circles and their diameter.

© 2009 Optical Society of America

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    [CrossRef]
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    [CrossRef]
  3. Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, W. R. Tribe, and M. C. Kemp, "Detection and identification of explosives using terahertz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116(1-3) (2005).
    [CrossRef]
  4. 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, 9130-9141 (2006).
    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
  7. J. Ahn, A. V. Efimov, R. D. Averitt, and A. J. Taylor, "Terahertz waveform synthesis via optical rectification of shaped ultrafast pulses," Opt. Express 11, 2486-2496 (2003).
    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  11. R. Chakkittakandy, J. A. W. M. Corver, and P. C. M. Planken, "Quasi-near field terahertz generation and detection," Opt. Express 16, 12794-12805 (2008)
    [PubMed]

2008

2007

K. Reinmann, "Table-top sources of ultrashort THz pulses," Rep. Prog. Phys. 70, 1597-1632 (2007).
[CrossRef]

2006

2005

A. G. Stepanov, J. Hebling, and J. Kuhl, "THz generation via optical rectification with ultrashort laser pulse focused to a line," Appl. Phys. B 81, 23-26 (2005)
[CrossRef]

2003

2002

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

2001

R. M. Koehl and K. Nelson, "Terahertz polaritonics: automated spatiotemporal control over propagating lattice waves," Chem. Phys. 267, 151-159 (2001).
[CrossRef]

1984

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov Radiation from Femtosecond Optical Pulses in Electro-Optic Media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Ahn, J.

Ahn, Y. H.

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

Auston, D. H.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov Radiation from Femtosecond Optical Pulses in Electro-Optic Media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Averitt, R. D.

Chakkittakandy, R.

Cheung, K. P.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov Radiation from Femtosecond Optical Pulses in Electro-Optic Media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Corver, J. A. W. M.

Efimov, A. V.

Hebling, J.

A. G. Stepanov, J. Hebling, and J. Kuhl, "THz generation via optical rectification with ultrashort laser pulse focused to a line," Appl. Phys. B 81, 23-26 (2005)
[CrossRef]

Kim, D. S.

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

Kleinman, D. A.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov Radiation from Femtosecond Optical Pulses in Electro-Optic Media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Koehl, R. M.

R. M. Koehl and K. Nelson, "Terahertz polaritonics: automated spatiotemporal control over propagating lattice waves," Chem. Phys. 267, 151-159 (2001).
[CrossRef]

Kuhl, J.

A. G. Stepanov, J. Hebling, and J. Kuhl, "THz generation via optical rectification with ultrashort laser pulse focused to a line," Appl. Phys. B 81, 23-26 (2005)
[CrossRef]

Nelson, K.

R. M. Koehl and K. Nelson, "Terahertz polaritonics: automated spatiotemporal control over propagating lattice waves," Chem. Phys. 267, 151-159 (2001).
[CrossRef]

Oh, E.

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

Park, D. J.

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

Pickwell, E.

E. Pickwell and V. P. Wallace, "Biomedical applications of terahertz technology," J. Phys. D: Appl. Phys. 39R301-R310 (2006).
[CrossRef]

Planken, P. C. M.

Redo-Sanchez, A.

Reinmann, K.

K. Reinmann, "Table-top sources of ultrashort THz pulses," Rep. Prog. Phys. 70, 1597-1632 (2007).
[CrossRef]

Sohn, J. Y.

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

Stepanov, A. G.

A. G. Stepanov, J. Hebling, and J. Kuhl, "THz generation via optical rectification with ultrashort laser pulse focused to a line," Appl. Phys. B 81, 23-26 (2005)
[CrossRef]

Taylor, A. J.

Valdmanis, J. A.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov Radiation from Femtosecond Optical Pulses in Electro-Optic Media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Wallace, V. P.

E. Pickwell and V. P. Wallace, "Biomedical applications of terahertz technology," J. Phys. D: Appl. Phys. 39R301-R310 (2006).
[CrossRef]

Zhang, X. -C.

Zhong, H.

Appl. Phys. B

A. G. Stepanov, J. Hebling, and J. Kuhl, "THz generation via optical rectification with ultrashort laser pulse focused to a line," Appl. Phys. B 81, 23-26 (2005)
[CrossRef]

Appl. Phys. Lett.

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim, "Tunable terahertz generation using femtosecond pulse shaping," Appl. Phys. Lett. 81, 13-15 (2002).
[CrossRef]

Chem. Phys.

R. M. Koehl and K. Nelson, "Terahertz polaritonics: automated spatiotemporal control over propagating lattice waves," Chem. Phys. 267, 151-159 (2001).
[CrossRef]

J. Phys. D: Appl. Phys.

E. Pickwell and V. P. Wallace, "Biomedical applications of terahertz technology," J. Phys. D: Appl. Phys. 39R301-R310 (2006).
[CrossRef]

Opt. Express

Phys. Rev. Lett.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov Radiation from Femtosecond Optical Pulses in Electro-Optic Media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Rep. Prog. Phys.

K. Reinmann, "Table-top sources of ultrashort THz pulses," Rep. Prog. Phys. 70, 1597-1632 (2007).
[CrossRef]

Other

Y. C. Shen, T. Lo, P. F. Taday, B. E. Cole, W. R. Tribe, and M. C. Kemp, "Detection and identification of explosives using terahertz pulsed spectroscopic imaging," Appl. Phys. Lett. 86, 241116(1-3) (2005).
[CrossRef]

J.-P. Caumes, L. Videau, C. Rouyer, and E. Freysz, "Kerr-like nonlinearity induced via TeraHertz generation and the electro-optical effect in Zinc Blende crystals," Phys. Rev. Lett. 28, 047401(1-4) (2002).
[CrossRef]

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Figures (5)

Fig. 1.
Fig. 1.

Theoretical spatiotemporal behavior, at different positions along the propagation axis, of a THz pulse emitted by a ZnTe crystal, in which the NIR pump cross-section geometry is represented by two concentric circles. The two circles have radii of 2 mm and 7 mm and a thickness of 200 μm.

Fig. 2.
Fig. 2.

Experimental setup. The THz generating and the detecting ZnTe have a thickness of 1 mm.

Fig. 3.
Fig. 3.

Experimental results (figures 3(a), 3(c), 3(e)) and corresponding numerical simulations (figures 3(b), 3(d), 3(f)) for THz spectra obtained by optical rectification in ZnTe under two concentric circles configurations of the pump laser beam profile. The insets show input beam rings. Each time, spectral amplitudes are normalized.

Fig. 4.
Fig. 4.

THz peak spectral amplitude against the position of the detecting ZnTe crystal along z. THz radiation shows interesting “self-focusing” properties. The “focal” position changes with the radius values of the circles. Fig. 4a) Experiment (the insets show representative ring configuration, lines are guides for eyes); Fig. 4b) simulations.

Fig. 5.
Fig. 5.

Fig. 5a) Multi-mode theoretical THz spectra obtained with a two circle configuration (radiuses of 3 mm and 9 mm), at 2.5 cm (solid line) and 2.9 cm (dashed line) from the generating ZnTe. Fig. 5b) Narrow-band THz theoretical spectra obtained with a five circle configuration (radiuses of 11, 12, 13, 14 and 15 mm) at 3 cm (solid line) and 4cm (dashed line) from the generating ZnTe. Each time the initial THz spectrum is shown (dash-dotted line).

Equations (3)

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EΩkz=EΩkz02{eik(Ω)(zz0)[1+r2/2(zz0)2]iλ(zz0)}
EΩkz0=iz0G(k)k(Ω)+Ω/vgΩ2c2χ2(Ω)C(Ω)eiz02[k(Ω)+Ω/vg]sinc[z02Δ(Ω)]
G(k)=2π0F(r)J0(kr)rdr

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