Abstract

A method for increasing the stability of terahertz (THz) time-domain spectrometers utilizing electro-optic balanced detection is presented in this paper. The stability of these systems is sensitive to optical alignment and polarization quality; small changes in temperature, pressure, stress, and strain can all affect SNR. High stability is achieved by precise rotation of the quarter-wave plate (QWP) balance position during the operation of the THz spectrometer. Providing feedback via QWP rotation optimizes the noise floor with minimal modulation to the THz signal in a nonideal optical system. Applying active balance control eliminates constant tuning by the operator between scans, after purging with dry nitrogen, applying vacuum, and during system setup.

© 2009 IEEE

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  1. A. J. Fitzgerald, B. E. Cole, P. F. Taday, "Nondestructive analysis of tablet coating thicknesses using terahertz pulsed imaging," J. Pharm. Sci. 94, 177-183 (2005).
  2. D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).
  3. K. Kawase, Y. Ogawa, Y. Watanabe, H. Inoue, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Exp. 11, 2549-2554 (2003).
  4. M. C. Kemp, P. F. Taday, B. E. Cole, J. A. Cluff, A. J. Fitzgerald, W. R. Tribe, "Security applications of terahertz technology," Proc. SPIE 5070, 44-52 (2003).
  5. P. H. Siegel, "Terahertz technology in biology and medicine," IEEE Trans. Microw. Theory Techn. 52, 2438-2447 (2004).
  6. “T-Ray™ 4000 pulsed terahertz controller,” Picometrix, LLCAnn ArborMI (2007) http://www.advancedphotonix.com/ap_products/terahertz_tr4000.asp.
  7. G. Gallot, D. Grischkowsky, "Electro-optic detection of terahertz radiation," J. Opt. Soc. Amer. B 16, 1204-1212 (1999).
  8. Q. Wu, X.-C. Zhang, "Free-space electro-optic sampling of terahertz beams," Appl. Phys. Lett. 67, 3523-3525 (1995).
  9. E. Hecht, Hecht Optics (Addison Wesley Longman, 1998) pp. 369-371.

2005

A. J. Fitzgerald, B. E. Cole, P. F. Taday, "Nondestructive analysis of tablet coating thicknesses using terahertz pulsed imaging," J. Pharm. Sci. 94, 177-183 (2005).

2004

P. H. Siegel, "Terahertz technology in biology and medicine," IEEE Trans. Microw. Theory Techn. 52, 2438-2447 (2004).

2003

K. Kawase, Y. Ogawa, Y. Watanabe, H. Inoue, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Exp. 11, 2549-2554 (2003).

M. C. Kemp, P. F. Taday, B. E. Cole, J. A. Cluff, A. J. Fitzgerald, W. R. Tribe, "Security applications of terahertz technology," Proc. SPIE 5070, 44-52 (2003).

1999

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).

G. Gallot, D. Grischkowsky, "Electro-optic detection of terahertz radiation," J. Opt. Soc. Amer. B 16, 1204-1212 (1999).

1995

Q. Wu, X.-C. Zhang, "Free-space electro-optic sampling of terahertz beams," Appl. Phys. Lett. 67, 3523-3525 (1995).

Appl. Phys. B

D. M. Mittleman, M. Gupta, R. Neelamani, R. G. Baraniuk, J. V. Rudd, M. Koch, "Recent advances in terahertz imaging," Appl. Phys. B 68, 1085-1094 (1999).

Appl. Phys. Lett.

Q. Wu, X.-C. Zhang, "Free-space electro-optic sampling of terahertz beams," Appl. Phys. Lett. 67, 3523-3525 (1995).

IEEE Trans. Microw. Theory Techn.

P. H. Siegel, "Terahertz technology in biology and medicine," IEEE Trans. Microw. Theory Techn. 52, 2438-2447 (2004).

J. Opt. Soc. Amer. B

G. Gallot, D. Grischkowsky, "Electro-optic detection of terahertz radiation," J. Opt. Soc. Amer. B 16, 1204-1212 (1999).

J. Pharm. Sci.

A. J. Fitzgerald, B. E. Cole, P. F. Taday, "Nondestructive analysis of tablet coating thicknesses using terahertz pulsed imaging," J. Pharm. Sci. 94, 177-183 (2005).

Opt. Exp.

K. Kawase, Y. Ogawa, Y. Watanabe, H. Inoue, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints," Opt. Exp. 11, 2549-2554 (2003).

Proc. SPIE

M. C. Kemp, P. F. Taday, B. E. Cole, J. A. Cluff, A. J. Fitzgerald, W. R. Tribe, "Security applications of terahertz technology," Proc. SPIE 5070, 44-52 (2003).

Other

“T-Ray™ 4000 pulsed terahertz controller,” Picometrix, LLCAnn ArborMI (2007) http://www.advancedphotonix.com/ap_products/terahertz_tr4000.asp.

E. Hecht, Hecht Optics (Addison Wesley Longman, 1998) pp. 369-371.

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