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Proceedings Paper

Noise analysis in THz time-domain spectroscopy and accuracy enhancement of optical constant determination
Author(s): Lionel Duvillaret; Frederic Garet; Jean-Louis Coutaz
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Paper Abstract

THz time-domain spectroscopy is a powerful and fast technique for measuring the optical constants of materials over a wide frequency range. In this paper, we analyze the weight of the different error terms on the optical constants determination. The different sources of noise are taken into account in a phenomenological way and the noise power can be expressed as a second order polynomial function of the complex transmission coefficient modulus (rho) of the sample under test. Then, for given experimental conditions, the accuracy on the optical constants determination depends on (rho) . In the case of optically thick sample, the echoes of the THz pulse, caused by multiple reflections into the sample, are temporally well separated and can be time- windowed. For each echo, (rho) can be measured and it depends on the echo number. We demonstrate that the precision on the optical constants is greatly enhanced using the pth echo, the value of p depending on the material refractive index and absorption. Moreover, as the coefficients of the polynomial function can be easily experimentally evaluated, quantitative information on the sources of noise is deduced.

Paper Details

Date Published: 29 April 1999
PDF: 11 pages
Proc. SPIE 3617, Terahertz Spectroscopy and Applications, (29 April 1999); doi: 10.1117/12.347129
Show Author Affiliations
Lionel Duvillaret, Univ. of Savoy (France)
Frederic Garet, Univ. of Savoy (France)
Jean-Louis Coutaz, Univ. of Savoy (France)

Published in SPIE Proceedings Vol. 3617:
Terahertz Spectroscopy and Applications
Mark S. Sherwin, Editor(s)

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