Abstract

Finite pump-beam size in optical pump–terahertz (THz) probe experiments introduces distortions in both the signal amplitude and the spectral form. We show both experimentally and analytically that the pump beam must be 3–4 times larger than the THz probe beam for a one-photon excitation process to achieve <10% spectral distortion. Our experiments use thin samples of single-crystal ZnTe or CdTe. Our model treats the pump-induced change in the THz probe field as radiation from a photoinduced current driven by the THz field. Interpretation of nonideal measurements and relaxation of the requirement on the pump-beam size by introduction of a metallic aperture are also discussed.

© 2006 Optical Society of America

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  1. C. A. Schmuttenmaer, "Exploring dynamics in the far-infrared with terahertz spectroscopy," Chem. Rev. 104, 1759-1780 (2004) and references therein.
    [CrossRef] [PubMed]
  2. M. C. Beard, G. M. Turner, and C. A. Schmuttenmaer, "Terahertz spectroscopy," J. Phys. Chem. B 106, 7146-7159 (2002).
    [CrossRef]
  3. E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
    [CrossRef] [PubMed]
  4. A. Nahata and T. F. Heinz, "Reshaping of freely propagating terahertz pulses by diffraction," IEEE J. Sel. Top. Quantum Electron. 2, 701-708 (1996).
    [CrossRef]
  5. J. Bromage, S. Radic, G. P. Agrawal, C. R. Stroud, Jr., P. M. Fauchet, and R. Sobolevski, "Spatiotemporal shaping of half-cycle terahertz pulses by diffraction through conductive apertured of finite thickness," J. Opt. Soc. Am. B 15, 1953-1959 (1998).
    [CrossRef]
  6. O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
    [CrossRef]
  7. R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
    [CrossRef]
  8. I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
    [CrossRef]
  9. G. L. Dakovski, B. Kubera, and J. Shan, "Localized THz generation via optical rectification in ZnTe," J. Opt. Soc. Am. B 23, 1667-1670(2005).
    [CrossRef]

2005 (1)

G. L. Dakovski, B. Kubera, and J. Shan, "Localized THz generation via optical rectification in ZnTe," J. Opt. Soc. Am. B 23, 1667-1670(2005).
[CrossRef]

2004 (2)

C. A. Schmuttenmaer, "Exploring dynamics in the far-infrared with terahertz spectroscopy," Chem. Rev. 104, 1759-1780 (2004) and references therein.
[CrossRef] [PubMed]

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

2002 (3)

M. C. Beard, G. M. Turner, and C. A. Schmuttenmaer, "Terahertz spectroscopy," J. Phys. Chem. B 106, 7146-7159 (2002).
[CrossRef]

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

2001 (1)

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

1998 (1)

1996 (1)

A. Nahata and T. F. Heinz, "Reshaping of freely propagating terahertz pulses by diffraction," IEEE J. Sel. Top. Quantum Electron. 2, 701-708 (1996).
[CrossRef]

Agrawal, G. P.

Alves, H. W. Leite

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Alves, J. L. A.

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Beard, M. C.

M. C. Beard, G. M. Turner, and C. A. Schmuttenmaer, "Terahertz spectroscopy," J. Phys. Chem. B 106, 7146-7159 (2002).
[CrossRef]

Belas, E.

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

Bonn, M.

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

Bromage, J.

Dakovski, G. L.

G. L. Dakovski, B. Kubera, and J. Shan, "Localized THz generation via optical rectification in ZnTe," J. Opt. Soc. Am. B 23, 1667-1670(2005).
[CrossRef]

de Oliveira, C.

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

de Paiva, R.

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Fauchet, P. M.

Franc, J.

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

Gill, R.

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

Heinz, T. F.

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

A. Nahata and T. F. Heinz, "Reshaping of freely propagating terahertz pulses by diffraction," IEEE J. Sel. Top. Quantum Electron. 2, 701-708 (1996).
[CrossRef]

Hoschl, P.

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

Hsu, J. W. P.

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Knoesel, E.

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

Kubera, B.

G. L. Dakovski, B. Kubera, and J. Shan, "Localized THz generation via optical rectification in ZnTe," J. Opt. Soc. Am. B 23, 1667-1670(2005).
[CrossRef]

Lee, M.

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Leite, J. R.

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Mitrofanov, O.

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Moravec, P.

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

Nahata, A.

A. Nahata and T. F. Heinz, "Reshaping of freely propagating terahertz pulses by diffraction," IEEE J. Sel. Top. Quantum Electron. 2, 701-708 (1996).
[CrossRef]

Nogueira, R. A.

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Pfeiffer, L. N.

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Radic, S.

Schmuttenmaer, C. A.

C. A. Schmuttenmaer, "Exploring dynamics in the far-infrared with terahertz spectroscopy," Chem. Rev. 104, 1759-1780 (2004) and references therein.
[CrossRef] [PubMed]

M. C. Beard, G. M. Turner, and C. A. Schmuttenmaer, "Terahertz spectroscopy," J. Phys. Chem. B 106, 7146-7159 (2002).
[CrossRef]

Scolfaro, L. M. R.

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Shan, J.

G. L. Dakovski, B. Kubera, and J. Shan, "Localized THz generation via optical rectification in ZnTe," J. Opt. Soc. Am. B 23, 1667-1670(2005).
[CrossRef]

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

Sobolevski, R.

Stroud, C. R.

Turkevych, I.

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

Turner, G. M.

M. C. Beard, G. M. Turner, and C. A. Schmuttenmaer, "Terahertz spectroscopy," J. Phys. Chem. B 106, 7146-7159 (2002).
[CrossRef]

Wang, F.

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

West, K. W.

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Wynn, J. D.

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Appl. Phys. Lett. (1)

O. Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, and J. D. Wynn, "Terahertz pulse propagation through small apertures," Appl. Phys. Lett. 79, 907-909 (2001).
[CrossRef]

Braz. J. Phys. (1)

R. de Paiva, R. A. Nogueira, C. de Oliveira, H. W. Leite Alves, J. L. A. Alves, L. M. R. Scolfaro, and J. R. Leite, "First principle calculations of the effective mass parameters of AlxGa1-xN and ZnxCd1-xTe alloys," Braz. J. Phys. 32, 405-408 (2002).
[CrossRef]

Chem. Rev. (1)

C. A. Schmuttenmaer, "Exploring dynamics in the far-infrared with terahertz spectroscopy," Chem. Rev. 104, 1759-1780 (2004) and references therein.
[CrossRef] [PubMed]

IEEE J. Sel. Top. Quantum Electron. (1)

A. Nahata and T. F. Heinz, "Reshaping of freely propagating terahertz pulses by diffraction," IEEE J. Sel. Top. Quantum Electron. 2, 701-708 (1996).
[CrossRef]

J. Chem. Phys. (1)

E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, "Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy," J. Chem. Phys. 121, 394-404 (2004).
[CrossRef] [PubMed]

J. Opt. Soc. Am. B (2)

J. Phys. Chem. B (1)

M. C. Beard, G. M. Turner, and C. A. Schmuttenmaer, "Terahertz spectroscopy," J. Phys. Chem. B 106, 7146-7159 (2002).
[CrossRef]

Semicond. Sci. Technol. (1)

I. Turkevych, R. Gill, J. Franc, E. Belas, P. Hoschl, and P. Moravec, "High-temperature electron and hole mobility in CdTe," Semicond. Sci. Technol. 17, 1064-1066 (2002).
[CrossRef]

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Figures (3)

Fig. 1
Fig. 1

(a) Complex conductivity of photoinduced carriers in CdTe at room temperature as a function of frequency for pump sizes of 3.6 mm FWHM (solid curves) and 0.7 mm (dashed curves). Fit to the Drude model is shown for 3.6 mm pump (grey curves). (b) Pump-size dependence of σ ( ω ) 2 at 0.45 (open circles) and 1.15 THz (closed circles). The curves show the fits to Eq. (1a) as described in the text.

Fig. 2
Fig. 2

Simulation of the radiation power at 0.45 (dashed curve) and 1.15 THz (solid curve) emitted from a source of a fixed-peak polarization but with varying sizes. The radiation is collected by off-axis parabolic mirrors of 64 mm in diameter and 120 mm in focal length as used in the experiment. Results are rescaled to match at small source sizes. Critical sizes a c for the transition from the a 4 to the a 2 dependence are indicated for both frequencies. The illustrated size dependence also describes the dependence of the pump-induced signal Δ E ( ω ) on the pump- and probe-beam sizes.

Fig. 3
Fig. 3

(a) Density (open circles) and (b) mobility (open squares) of photoinduced carriers in CdTe inferred from the fit of the measurement to the Drude model over a range of pump beam sizes. Data that cannot be described by the Drude model are indicated by an ‘x’. Line in (a) is a fit to Eq. (1a), and filled circles are inferred peak carrier density, as described in the text.

Equations (2)

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Δ E norm ( ω ) 2 = ( α 2 1 + α 2 ) 2 , a probe < a c ,
= α 2 1 + α 2 , a probe > a c .

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