Accurate determination of optical coefficients from chemical samples using terahertz time-domain spectroscopy and effective medium theory
Optics Letters, Vol. 34, Issue 23, pp. 3722-3724 (2009)
http://dx.doi.org/10.1364/OL.34.003722
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Abstract
A technique for calculating the optical constants of powdered materials that have been pressed into pellets along with a diluent such as polyethylene, as is commonly used in the spectroscopy community, is introduced. The simple Beer–Lambert law typically used to calculate the optical constants has the inherent weakness that it treats the absorbing medium as a single nonporous solid, as opposed to a dielectric material embedded within a medium. This leads to a systematic underestimation of both the absorption coefficient and the refractive index, especially at low filling factors. Effective medium theory provides a way to calculate more accurate optical constants and produces similar optical constants across a wide range of filling factors, including crucially at the low filling factors commonly used experimentally. The technique can also be extended to estimate the porosity of the samples and provide a true, preparation-independent value for the optical properties of the sample material.
© 2009 Optical Society of America
OCIS Codes
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(160.4760) Materials : Optical properties
(300.1030) Spectroscopy : Absorption
(300.6495) Spectroscopy : Spectroscopy, teraherz
ToC Category:
Materials
History
Original Manuscript: September 1, 2009
Manuscript Accepted: October 2, 2009
Published: November 25, 2009
Citation
Edward P. Parrott, J. Axel Zeitler, and Lynn F. Gladden, "Accurate determination of optical coefficients from chemical samples using terahertz time-domain spectroscopy and effective medium theory," Opt. Lett. 34, 3722-3724 (2009)
http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-34-23-3722
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