Abstract

We present a flexible technology to generate broadband antireflection (AR) structures for the terahertz (THz) frequency range on planar and curved surfaces of silicon optics. Ultrashort laser pulses are used to ablate the surface to form a pattern of conical pillars with a period of 30 μm. These subwavelength structures act as an effective medium with gradual transition of the refractive index from air to silicon, which reduces the Fresnel reflection losses. The characterization with the THz time-domain spectroscopy system shows an AR effect for a frequency range of 0.1–1.5 THz with a maximum enhancement of the spectral amplitude by ca. 32% at 0.4 THz for planar surfaces. In addition, we demonstrate laser-generated AR structures on convex silicon lenses of both photoconductive emitter and detector devices. Here, the THz pulse amplitude can be increased by about 28%, and single frequencies even show an improvement of the spectral amplitude up to 58%.

© 2014 Optical Society of America

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References

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  1. D. Grischkowsky, S. Keiding, M. van Exter, and C. Fattinger, “Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors,” J. Opt. Soc. Am. B 7, 2006–2015 (1990).
    [CrossRef]
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    [CrossRef]
  3. B. Ferguson, S. Wang, D. Gray, D. Abbot, and X. C. Zhang, “T-ray computed tomography,” Opt. Lett. 27, 1312–1314 (2002).
    [CrossRef]
  4. B. Ferguson and X. C. Zhang, “Materials for terahertz science and technology,” Nat. Mater. 1, 26–33 (2002).
    [CrossRef]
  5. 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 (2005).
    [CrossRef]
  6. C. Jansen, S. Wietzke, O. Peters, M. Scheller, N. Vieweg, M. Salhi, N. Krumbholz, C. Jördens, T. Hochrein, and M. Koch, “Terahertz imaging: applications and perspectives,” Appl. Opt. 49, E48–E57 (2010).
    [CrossRef]
  7. C. Brückner, B. Pradarutti, R. Müller, S. Riehemann, G. Notni, and A. Tünnermann, “Design and evaluation of a THz time domain imaging system using standard optical design software,” Appl. Opt. 47, 4994–5006 (2008).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  11. M. Wichmann, A. S. Mondol, N. Kocic, S. Lippert, T. Probst, M. Schwerdtfeger, S. Schumann, T. Hochrein, P. Heidemeyer, M. Bastian, G. Bastian, and M. Koch, “Terahertz plastic compound lenses,” Appl. Opt. 52, 4186–4191 (2013).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  14. I. Hosako, “Multilayer optical thin films for use at terahertz frequencies: method of fabrication,” Appl. Opt. 44, 3769–3773 (2005).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]

2013 (2)

2011 (2)

2010 (2)

C. Jansen, S. Wietzke, O. Peters, M. Scheller, N. Vieweg, M. Salhi, N. Krumbholz, C. Jördens, T. Hochrein, and M. Koch, “Terahertz imaging: applications and perspectives,” Appl. Opt. 49, E48–E57 (2010).
[CrossRef]

A. Brahm, M. Kunz, S. Riehemann, G. Notni, and A. Tünnermann, “Volumetric spectral analysis of materials using terahertz-tomography techniques,” Appl. Phys. B 100, 151–158 (2010).
[CrossRef]

2009 (1)

2008 (1)

2005 (2)

I. Hosako, “Multilayer optical thin films for use at terahertz frequencies: method of fabrication,” Appl. Opt. 44, 3769–3773 (2005).
[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 terahertz pulsed spectroscopic imaging,” Appl. Phys. Lett. 86, 241116 (2005).
[CrossRef]

2004 (1)

2002 (2)

B. Ferguson, S. Wang, D. Gray, D. Abbot, and X. C. Zhang, “T-ray computed tomography,” Opt. Lett. 27, 1312–1314 (2002).
[CrossRef]

B. Ferguson and X. C. Zhang, “Materials for terahertz science and technology,” Nat. Mater. 1, 26–33 (2002).
[CrossRef]

2000 (1)

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

1998 (1)

1997 (2)

1991 (1)

1990 (2)

D. Grischkowsky, S. Keiding, M. van Exter, and C. Fattinger, “Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors,” J. Opt. Soc. Am. B 7, 2006–2015 (1990).
[CrossRef]

M. van Exter and D. R. Grischkowsky, “Characterization of an optoelectronic terahertz beam system,” IEEE Trans. Microwave Theor. Tech. 38, 1684–1691 (1990).
[CrossRef]

1986 (1)

1983 (1)

J. Y. L. Ma and L. C. Robinson, “Night moth eye window for the millimetre and sub-millimetre wave region,” Opt. Acta 30, 1685–1695 (1983).
[CrossRef]

1973 (1)

P. B. Clapham and M. C. Hutley, “Reduction of lens reflection by the ‘moth eye’ principle,” Nature 244, 281–282 (1973).
[CrossRef]

Abbot, D.

Baird, W. E.

Bastian, G.

Bastian, M.

Beall, J.

Boivin, L.

Brahm, A.

A. Brahm, M. Kunz, S. Riehemann, G. Notni, and A. Tünnermann, “Volumetric spectral analysis of materials using terahertz-tomography techniques,” Appl. Phys. B 100, 151–158 (2010).
[CrossRef]

Britton, J.

Brückner, C.

Clapham, P. B.

P. B. Clapham and M. C. Hutley, “Reduction of lens reflection by the ‘moth eye’ principle,” Nature 244, 281–282 (1973).
[CrossRef]

Cole, B. E.

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 (2005).
[CrossRef]

Dai, J.

Datta, R.

Devlin, M. J.

Dietz, R. J. B.

Döring, S.

S. Döring, S. Richter, A. Tünnermann, and S. Nolte, “Evolution of hole depth and shape in ultrashort pulse deep drilling in silicon,” Appl. Phys. A 105, 69–74 (2011).
[CrossRef]

Fattinger, C.

Ferguson, B.

B. Ferguson, S. Wang, D. Gray, D. Abbot, and X. C. Zhang, “T-ray computed tomography,” Opt. Lett. 27, 1312–1314 (2002).
[CrossRef]

B. Ferguson and X. C. Zhang, “Materials for terahertz science and technology,” Nat. Mater. 1, 26–33 (2002).
[CrossRef]

Fowler, J.

Gallardo, P.

Gatesman, A. J.

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

Gaylord, T. K.

Gerhard, M.

Gray, D.

Grischkowsky, D.

Grischkowsky, D. R.

M. van Exter and D. R. Grischkowsky, “Characterization of an optoelectronic terahertz beam system,” IEEE Trans. Microwave Theor. Tech. 38, 1684–1691 (1990).
[CrossRef]

Heidemeyer, P.

Hiromoto, N.

Hochrein, T.

Hosako, I.

Hubmayr, J.

Hunsche, S.

Hutley, M. C.

P. B. Clapham and M. C. Hutley, “Reduction of lens reflection by the ‘moth eye’ principle,” Nature 244, 281–282 (1973).
[CrossRef]

Irwin, K.

Jansen, C.

Ji, M.

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

Jördens, C.

Käsebier, T.

Kawase, K.

Keiding, S.

Kemp, M. C.

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 (2005).
[CrossRef]

Koch, M.

Kocic, N.

Krumbholz, N.

Kunz, M.

A. Brahm, M. Kunz, S. Riehemann, G. Notni, and A. Tünnermann, “Volumetric spectral analysis of materials using terahertz-tomography techniques,” Appl. Phys. B 100, 151–158 (2010).
[CrossRef]

Lalanne, P.

Lemercier-Lalanne, D.

Lippert, S.

Lo, T.

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 (2005).
[CrossRef]

Ma, J. Y. L.

J. Y. L. Ma and L. C. Robinson, “Night moth eye window for the millimetre and sub-millimetre wave region,” Opt. Acta 30, 1685–1695 (1983).
[CrossRef]

McMahon, J. J.

Mittleman, D. M.

Moharam, M. G.

Mondol, A. S.

Müller, R.

Munson, C. D.

Musante, C.

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

Newburgh, L.

Nibarger, J. P.

Niemack, M. D.

Nolte, S.

S. Döring, S. Richter, A. Tünnermann, and S. Nolte, “Evolution of hole depth and shape in ultrashort pulse deep drilling in silicon,” Appl. Phys. A 105, 69–74 (2011).
[CrossRef]

Notni, G.

Nuss, M. C.

Page, L.

Peters, O.

Pradarutti, B.

Probst, T.

Quijada, M. A.

Richter, S.

S. Döring, S. Richter, A. Tünnermann, and S. Nolte, “Evolution of hole depth and shape in ultrashort pulse deep drilling in silicon,” Appl. Phys. A 105, 69–74 (2011).
[CrossRef]

Riehemann, S.

Robinson, L. C.

J. Y. L. Ma and L. C. Robinson, “Night moth eye window for the millimetre and sub-millimetre wave region,” Opt. Acta 30, 1685–1695 (1983).
[CrossRef]

Salhi, M.

Sartorius, B.

Schell, M.

Scheller, M.

Schmitt, B. L.

Schumann, S.

Schwerdtfeger, M.

Shen, Y. C.

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 (2005).
[CrossRef]

Southwell, W. H.

Staggs, S. T.

Stanze, D.

Taday, P. F.

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 (2005).
[CrossRef]

Thornton, R.

Tribe, W. R.

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 (2005).
[CrossRef]

Tünnermann, A.

S. Döring, S. Richter, A. Tünnermann, and S. Nolte, “Evolution of hole depth and shape in ultrashort pulse deep drilling in silicon,” Appl. Phys. A 105, 69–74 (2011).
[CrossRef]

A. Brahm, M. Kunz, S. Riehemann, G. Notni, and A. Tünnermann, “Volumetric spectral analysis of materials using terahertz-tomography techniques,” Appl. Phys. B 100, 151–158 (2010).
[CrossRef]

C. Brückner, T. Käsebier, B. Pradarutti, S. Riehemann, G. Notni, and A. Tünnermann, “Broadband antireflective structures applied to high resistive float zone silicon in the THz spectral range,” Opt. Express 17, 3063–3077 (2009).
[CrossRef]

C. Brückner, B. Pradarutti, R. Müller, S. Riehemann, G. Notni, and A. Tünnermann, “Design and evaluation of a THz time domain imaging system using standard optical design software,” Appl. Opt. 47, 4994–5006 (2008).
[CrossRef]

van Exter, M.

M. van Exter and D. R. Grischkowsky, “Characterization of an optoelectronic terahertz beam system,” IEEE Trans. Microwave Theor. Tech. 38, 1684–1691 (1990).
[CrossRef]

D. Grischkowsky, S. Keiding, M. van Exter, and C. Fattinger, “Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors,” J. Opt. Soc. Am. B 7, 2006–2015 (1990).
[CrossRef]

Vieweg, N.

Waldman, J.

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

Wang, S.

Wichmann, M.

Wietzke, S.

Wollack, E. J.

Yngvesson, S.

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

Zhang, J.

Zhang, L.

Zhang, W.

Zhang, X. C.

B. Ferguson and X. C. Zhang, “Materials for terahertz science and technology,” Nat. Mater. 1, 26–33 (2002).
[CrossRef]

B. Ferguson, S. Wang, D. Gray, D. Abbot, and X. C. Zhang, “T-ray computed tomography,” Opt. Lett. 27, 1312–1314 (2002).
[CrossRef]

Appl. Opt. (7)

C. Jansen, S. Wietzke, O. Peters, M. Scheller, N. Vieweg, M. Salhi, N. Krumbholz, C. Jördens, T. Hochrein, and M. Koch, “Terahertz imaging: applications and perspectives,” Appl. Opt. 49, E48–E57 (2010).
[CrossRef]

C. Brückner, B. Pradarutti, R. Müller, S. Riehemann, G. Notni, and A. Tünnermann, “Design and evaluation of a THz time domain imaging system using standard optical design software,” Appl. Opt. 47, 4994–5006 (2008).
[CrossRef]

M. Wichmann, A. S. Mondol, N. Kocic, S. Lippert, T. Probst, M. Schwerdtfeger, S. Schumann, T. Hochrein, P. Heidemeyer, M. Bastian, G. Bastian, and M. Koch, “Terahertz plastic compound lenses,” Appl. Opt. 52, 4186–4191 (2013).
[CrossRef]

K. Kawase and N. Hiromoto, “Terahertz-wave antireflection coating on Ge and GaAs with fused quartz,” Appl. Opt. 37, 1862–1866 (1998).
[CrossRef]

I. Hosako, “Multilayer optical thin films for use at terahertz frequencies: method of fabrication,” Appl. Opt. 44, 3769–3773 (2005).
[CrossRef]

R. Datta, C. D. Munson, M. D. Niemack, J. J. McMahon, J. Britton, E. J. Wollack, J. Beall, M. J. Devlin, J. Fowler, P. Gallardo, J. Hubmayr, K. Irwin, L. Newburgh, J. P. Nibarger, L. Page, M. A. Quijada, B. L. Schmitt, S. T. Staggs, R. Thornton, and L. Zhang, “Large-aperture wide-bandwidth antireflection-coated silicon lenses for millimeter wavelengths,” Appl. Opt. 52, 8747–8757 (2013).
[CrossRef]

T. K. Gaylord, W. E. Baird, and M. G. Moharam, “Zero-reflectivity high spatial-frequency rectangular-groove dielectric surface-relief gratings,” Appl. Opt. 25, 4562–4567 (1986).
[CrossRef]

Appl. Phys. A (1)

S. Döring, S. Richter, A. Tünnermann, and S. Nolte, “Evolution of hole depth and shape in ultrashort pulse deep drilling in silicon,” Appl. Phys. A 105, 69–74 (2011).
[CrossRef]

Appl. Phys. B (1)

A. Brahm, M. Kunz, S. Riehemann, G. Notni, and A. Tünnermann, “Volumetric spectral analysis of materials using terahertz-tomography techniques,” Appl. Phys. B 100, 151–158 (2010).
[CrossRef]

Appl. Phys. Lett. (1)

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 (2005).
[CrossRef]

IEEE Microwave Guided Wave Lett. (1)

A. J. Gatesman, J. Waldman, M. Ji, C. Musante, and S. Yngvesson, “An anti-reflection coating for silicon optics at terahertz frequencies,” IEEE Microwave Guided Wave Lett. 10, 264–266 (2000).
[CrossRef]

IEEE Trans. Microwave Theor. Tech. (1)

M. van Exter and D. R. Grischkowsky, “Characterization of an optoelectronic terahertz beam system,” IEEE Trans. Microwave Theor. Tech. 38, 1684–1691 (1990).
[CrossRef]

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

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

Nat. Mater. (1)

B. Ferguson and X. C. Zhang, “Materials for terahertz science and technology,” Nat. Mater. 1, 26–33 (2002).
[CrossRef]

Nature (1)

P. B. Clapham and M. C. Hutley, “Reduction of lens reflection by the ‘moth eye’ principle,” Nature 244, 281–282 (1973).
[CrossRef]

Opt. Acta (1)

J. Y. L. Ma and L. C. Robinson, “Night moth eye window for the millimetre and sub-millimetre wave region,” Opt. Acta 30, 1685–1695 (1983).
[CrossRef]

Opt. Express (2)

Opt. Lett. (2)

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Figures (11)

Fig. 1.
Fig. 1.

Side and top view of the statistic AR structure of sample A.

Fig. 2.
Fig. 2.

Side and top view of the homogeneous AR structure of sample B.

Fig. 3.
Fig. 3.

THz pulse transmission through a silicon wafer with AR structure of type A (red line) and a reference wafer without an AR structure (black line).

Fig. 4.
Fig. 4.

THz spectra of the measured THz pulses: reference spectrum (black line) and spectrum through an AR structure of type A (red line).

Fig. 5.
Fig. 5.

THz pulse transmission through a silicon wafer with AR structure of type B (red line) and a reference wafer without an AR structure (black line).

Fig. 6.
Fig. 6.

THz spectra of the measured THz pulses: reference spectrum (black line) and spectrum through an AR structure of type B (red line).

Fig. 7.
Fig. 7.

Reflected pulses from the backside of the silicon wafers of samples A and B.

Fig. 8.
Fig. 8.

SEM image of the AR-structured silicon lens.

Fig. 9.
Fig. 9.

THz TDS setup: fs laser; BS, beam splitter; THz emitter; PM, off-axis parabolic mirrors; THz detector; and an optical delay stage.

Fig. 10.
Fig. 10.

Time-resolved measurement with AR structures on the silicon lenses: reference without an AR structure (black line), structured emitter lens (red line), and AR structure on emitter and detector lens (blue line).

Fig. 11.
Fig. 11.

Spectral comparison: reference without an AR structure (black line), structured emitter lens (red line), and AR structure on emitter and detector lens (blue line).

Tables (2)

Tables Icon

Table 1. Spectral Comparison of the AR Structures of Samples A and B

Tables Icon

Table 2. Spectral Comparison of the AR Structures on the Silicon Lenses

Equations (2)

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Λλminnsi,
dλmax4neff,

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