Abstract

We describe an efficient and compact terahertz (THz) illumination system as part of an active THz imager. The design and fabrication methods are verified by comparing measurements with wave optical simulations that form a basis for the design of a Gaussian-to-tophat beam shaper. Introducing realistic alignment tolerances in the simulations led to an improved agreement with the experimental data. Furthermore, we propose a method to reduce the alignment effort for THz beam shaping elements by correlating measured results with simulated data of a misaligned system.

© 2010 Optical Society of America

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References

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  1. J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
    [CrossRef]
  2. E. R. Mueller, “Terahertz radiation: applications and sources,” Industrial Physicist 9(4), 27-29 (2003).
  3. F. M. Dickey and S. Holswade, “Gaussian beam shaping: diffraction theory and design,” Laser Beam Shaping: Theory and Techniques (CRC, 2000).
    [CrossRef]
  4. E. Noponen, A. Tamminen, and M. Vaaja, “Design of transmission-type phase holograms for a compact radar-cross-section measurement range at 650 GHz,” Appl. Opt. Vol. 46, 4181-4196 (2007).
    [CrossRef] [PubMed]
  5. J. F. Johansson and N. D. Whyborn, “The diagonal horn as a sub-millimeter wave antenna,” IEEE Trans. Microwave Theory Tech. 40, 795-800 (1992).
    [CrossRef]
  6. Virginia Diodes, Inc., “Nominal horn specifications,” http://virginiadiodes.com/VDI/pdf/VDI%20Feedhorn%20Summary%202009_04_30.pdf.
  7. C. Brückner, B. Pradarutti, O. Stenzel, R. Steinkopf, S. Riehemann, G. Notni, and A. Tünnermann, “Broadband antireflective surface-relief structure for THz optics,” Opt. Express 15, 779-789 (2007).
    [CrossRef] [PubMed]
  8. H. Aagedal, F. Wyrowski, M. Schmid, S. Egner, J. Müller-Quade, and T. Beth, “Analytical beam shaping with application to laser-diode arrays,” J. Opt. Soc. Am. A 14, 1549-1553 (1997).
    [CrossRef]
  9. R. W. Gerchberg and W. O. Saxton, “A practical algorithm for the determination of phase from image and diffraction plane figures,” Optik (Jena) 35, 237-246 (1972).
  10. S. Sinzinger and J. Jahns, Microoptics, 2nd ed. (Wiley-VCH, 2003).
    [CrossRef]
  11. S. Stoebenau and S. Sinzinger, “Ultraprecision machining techniques for the fabrication of freeform surfaces in highly integrated optical microsystems,” Proc. SPIE 7426, 742637 (2009).
  12. R. H. Abd El-Maksoud and J. M. Sasian, “Paraxial ghost image analysis,” Proc. SPIE 7428, 742807 (2009).
    [CrossRef]

2009 (2)

S. Stoebenau and S. Sinzinger, “Ultraprecision machining techniques for the fabrication of freeform surfaces in highly integrated optical microsystems,” Proc. SPIE 7426, 742637 (2009).

R. H. Abd El-Maksoud and J. M. Sasian, “Paraxial ghost image analysis,” Proc. SPIE 7428, 742807 (2009).
[CrossRef]

2007 (2)

2005 (1)

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

2003 (1)

E. R. Mueller, “Terahertz radiation: applications and sources,” Industrial Physicist 9(4), 27-29 (2003).

1997 (1)

1992 (1)

J. F. Johansson and N. D. Whyborn, “The diagonal horn as a sub-millimeter wave antenna,” IEEE Trans. Microwave Theory Tech. 40, 795-800 (1992).
[CrossRef]

1972 (1)

R. W. Gerchberg and W. O. Saxton, “A practical algorithm for the determination of phase from image and diffraction plane figures,” Optik (Jena) 35, 237-246 (1972).

Aagedal, H.

Abd El-Maksoud, R. H.

R. H. Abd El-Maksoud and J. M. Sasian, “Paraxial ghost image analysis,” Proc. SPIE 7428, 742807 (2009).
[CrossRef]

Barat, R.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Beth, T.

Brückner, C.

Dickey, F. M.

F. M. Dickey and S. Holswade, “Gaussian beam shaping: diffraction theory and design,” Laser Beam Shaping: Theory and Techniques (CRC, 2000).
[CrossRef]

Egner, S.

Federici, J. F.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Gary, D.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Gerchberg, R. W.

R. W. Gerchberg and W. O. Saxton, “A practical algorithm for the determination of phase from image and diffraction plane figures,” Optik (Jena) 35, 237-246 (1972).

Holswade, S.

F. M. Dickey and S. Holswade, “Gaussian beam shaping: diffraction theory and design,” Laser Beam Shaping: Theory and Techniques (CRC, 2000).
[CrossRef]

Huang, F.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Jahns, J.

S. Sinzinger and J. Jahns, Microoptics, 2nd ed. (Wiley-VCH, 2003).
[CrossRef]

Johansson, J. F.

J. F. Johansson and N. D. Whyborn, “The diagonal horn as a sub-millimeter wave antenna,” IEEE Trans. Microwave Theory Tech. 40, 795-800 (1992).
[CrossRef]

Mueller, E. R.

E. R. Mueller, “Terahertz radiation: applications and sources,” Industrial Physicist 9(4), 27-29 (2003).

Müller-Quade, J.

Noponen, E.

Notni, G.

Oliveira, F.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Pradarutti, B.

Riehemann, S.

Sasian, J. M.

R. H. Abd El-Maksoud and J. M. Sasian, “Paraxial ghost image analysis,” Proc. SPIE 7428, 742807 (2009).
[CrossRef]

Saxton, W. O.

R. W. Gerchberg and W. O. Saxton, “A practical algorithm for the determination of phase from image and diffraction plane figures,” Optik (Jena) 35, 237-246 (1972).

Schmid, M.

Schulkin, B.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Sinzinger, S.

S. Stoebenau and S. Sinzinger, “Ultraprecision machining techniques for the fabrication of freeform surfaces in highly integrated optical microsystems,” Proc. SPIE 7426, 742637 (2009).

S. Sinzinger and J. Jahns, Microoptics, 2nd ed. (Wiley-VCH, 2003).
[CrossRef]

Steinkopf, R.

Stenzel, O.

Stoebenau, S.

S. Stoebenau and S. Sinzinger, “Ultraprecision machining techniques for the fabrication of freeform surfaces in highly integrated optical microsystems,” Proc. SPIE 7426, 742637 (2009).

Tamminen, A.

Tünnermann, A.

Vaaja, M.

Whyborn, N. D.

J. F. Johansson and N. D. Whyborn, “The diagonal horn as a sub-millimeter wave antenna,” IEEE Trans. Microwave Theory Tech. 40, 795-800 (1992).
[CrossRef]

Wyrowski, F.

Zimdars, D.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Appl. Opt. (1)

IEEE Trans. Microwave Theory Tech. (1)

J. F. Johansson and N. D. Whyborn, “The diagonal horn as a sub-millimeter wave antenna,” IEEE Trans. Microwave Theory Tech. 40, 795-800 (1992).
[CrossRef]

Industrial Physicist (1)

E. R. Mueller, “Terahertz radiation: applications and sources,” Industrial Physicist 9(4), 27-29 (2003).

J. Opt. Soc. Am. A (1)

Opt. Express (1)

Optik (Jena) (1)

R. W. Gerchberg and W. O. Saxton, “A practical algorithm for the determination of phase from image and diffraction plane figures,” Optik (Jena) 35, 237-246 (1972).

Proc. SPIE (2)

S. Stoebenau and S. Sinzinger, “Ultraprecision machining techniques for the fabrication of freeform surfaces in highly integrated optical microsystems,” Proc. SPIE 7426, 742637 (2009).

R. H. Abd El-Maksoud and J. M. Sasian, “Paraxial ghost image analysis,” Proc. SPIE 7428, 742807 (2009).
[CrossRef]

Semicond. Sci. Technol. (1)

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications,” Semicond. Sci. Technol. 20, S266-S280 (2005).
[CrossRef]

Other (3)

Virginia Diodes, Inc., “Nominal horn specifications,” http://virginiadiodes.com/VDI/pdf/VDI%20Feedhorn%20Summary%202009_04_30.pdf.

S. Sinzinger and J. Jahns, Microoptics, 2nd ed. (Wiley-VCH, 2003).
[CrossRef]

F. M. Dickey and S. Holswade, “Gaussian beam shaping: diffraction theory and design,” Laser Beam Shaping: Theory and Techniques (CRC, 2000).
[CrossRef]

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Figures (7)

Fig. 1
Fig. 1

(a) Illustration of the active THz imaging system consisting of imaging (bright) and illumination unit (dark) with distance marks M0–M3 for the intensity measurements; (b) photo of the measurement setup for investigating the intensity distribution at 3 m ; and (c) schematic diagram of the detection system.

Fig. 2
Fig. 2

(a) GTBS in polypropylene; (b) design (black dotted line) and measured (red dashed line) profile of the GTBS, deviation of measured profile from computed shape (blue line)

Fig. 3
Fig. 3

Angular Gaussian intensity distribution emitted by the THz source measured with a Schottky diode.

Fig. 4
Fig. 4

(a) Measured, (b) simulated (ideal), and (c) simulated (misaligned) intensity distributions at 0.5 m behind the GTBS.

Fig. 5
Fig. 5

(a) Measured, (b) simulated (ideal), and (c) simulated (misaligned) intensity distributions at 1.5 m behind the GTBS.

Fig. 6
Fig. 6

(a) Measured, (b) simulated (ideal), and (c) simulated (misaligned) intensity distributions at 1.5 m behind the GTBS.

Fig. 7
Fig. 7

Cross sections of measured (red lines) and misaligned simulated (blue lines) intensity distributions at distances of (a) 0.5 m , (b) 1.5 m , and (c) 3.0 m behind the GTBS.

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