Abstract
Terahertz time-domain spectroscopy (THz-TDS) allows broadband noninvasive measurement of the optical parameters of various materials in the THz domain. The measurement accuracy of these parameters is highly influenced by the difficulty in distinguishing THz signals from unwanted signals such as noise, signal fluctuation, and multiple echoes, which directly affects material identification and characterization efficiency. We introduce a novel method that provides effective extraction and separation of THz signals from such undesired effects. The proposed algorithm was assessed through experiments that presented enhancement in material parameter evaluation, such as the decomposition of the sample-induced echoes (SIEs) from the complex THz sample signal with near-zero extraction error. Improved precision (\(\pm \)0.05\(\,\upmu \)m) was achieved in the determination of the sample thickness compared to that of the mechanical method (\(\pm \)10\(\,\upmu \)m). Furthermore, we could infer from the component concentration measurement results of a compound sample (44.2 % decrease in the root mean square concentration error) that the material parameter calculation accuracy had improved, proposing a means to enhance the ultimate nondestructive material evaluation performance.
Similar content being viewed by others
References
Siegel, P.H.: Terahertz technology in biology and medicine. IEEE Trans. Microw. Theory 52(10), 2438–2447 (2004). doi:10.1109/TMTT.2004.835916
Rutz, F., Koch, M., Khare, S., Moneke, M., Richter, H., Ewert, U.: Terahertz quality control of polymeric products. Int. J. Infrared Millim. Waves 27(4), 547–556 (2006). doi:10.1007/s10762-006-9106-7
Liu, H.-B., Zhong, H., Karpowicz, N., Chen, Y., Zhang, X.-C.: Terahertz spectroscopy and imaging for defense and security applications. Proc. IEEE 95(8), 1514–1527 (2007). doi:10.1109/JPROC.2007.898903
Leahy-Hoppa, M., Fitch, M., Osiander, R.: Terahertz spectroscopy techniques for explosives detection. Anal. Bioanal. Chem. 395(2), 247–257 (2009). doi:10.1007/s00216-009-2803-z
Lee, Y.-S.: Principles of Terahertz Science and Technology. Springer, New York (2009)
Zhang, X.-C., Xu, J.: Introduction to THz Wave Photonics. Springer, New York (2010)
Naito, K., Kagawa, Y., Utsuno, S., Naganuma, T., Kurihara, K.: Dielectric properties of eight-harness-stain fabric glass fiber reinforced polyimide matrix composite in the THz frequency range. NDT&E Int. 42(5), 441–445 (2009). doi:10.1016/j.ndteint.2009.02.001
Stoik, C., Bohn, M., Blackshire, J.: Nondestructive evaluation of aircraft composites using reflective terahertz time domain spectroscopy. NDT&E Int. 43(2), 106–115 (2010). doi:10.1016/j.ndteint.2009.09.005
Tanabe, T., Watanabe, K., Oyama, Y., Seo, K.: Polarization sensitive THz absorption spectroscopy for the evaluation of uniaxially deformed ultra-high molecular weight polyethylene. NDT&E Int. 43(4), 329–333 (2010). doi:10.1016/j.ndteint.2010.03.001
Duvillaret, L., Garet, F., Coutaz, J.-L.: A reliable method for extraction of material parameters in terahertz time-domain spectroscopy. IEEE J. Sel. Top. Quantum 2(3), 739–746 (1996). doi:10.1109/2944.571775
Duvillaret, L., Garet, F., Coutaz, J.-L.: Highly precise determination of optical constants and sample thickness in terahertz time-domain spectroscopy. Appl. Opt. 38(2), 409–415 (1999). doi:10.1364/AO.38.000409
Dorney, T., Baraniuk, R., Mittleman, D.: Material parameter estimation with terahertz time-domain spectroscopy. J. Opt. Soc. Am. A 18(7), 1562–1571 (2001). doi:10.1364/JOSAA.18.001562
Pupeza, I., Wilk, R., Koch, M.: Highly accurate optical material parameter determination with THz time-domain spectroscopy. Opt. Express 15(7), 4335–4350 (2007). doi:10.1364/OE.15.004335
Naftaly, M., Miles, R.E.: A method for removing etalon oscillations from THz time-domain spectra. Opt. Commun. 280(2), 291–295 (2007). doi:10.1016/j.optcom.2007.08.042
Ryu, C., Kong, S.: Atmospheric degradation correction of terahertz beams using multiscale signal restoration. Appl. Opt. 49(5), 927–935 (2010). doi:10.1364/AO.49.000927
Withayachumnankul, W., Fischer, B.M., Lin, H., Abbott, D.: Uncertainty in terahertz time-domain spectroscopy measurement. J. Opt. Soc. Am. B. 25(6), 1059–1072 (2008). doi:10.1364/JOSAB.25.001059
Jepsen, P.U., Keiding, S.R.: Radiation patterns from lens-coupled THz antennas. Opt. Lett. 20(8), 807–809 (1995). doi:10.1364/OL.20.000807
Choi, J., Ryu, S.Y., Kwon, W.S., Kim, K.-S., Kim, S.: Compound explosives detection and component analysis via terahertz time-domain spectroscopy. J. Opt. Soc. Korea 17(5), 454–460 (2013). doi:10.3807/JOSK.2013.17.5.454
Krüger, M., Funkner, S., Bründermann, E., Havenith, M.: Uncertainty and ambiguity in terahertz parameter extraction and data analysis. J. Infrared. Millim. Terahertz. Waves 32(5), 699–715 (2011). doi:10.1007/s10762-010-9669-1
Acknowledgments
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. NRF-2010-0017795).
Author information
Authors and Affiliations
Corresponding authors
Rights and permissions
About this article
Cite this article
Choi, J., Kwon, W.S., Kim, KS. et al. Nondestructive Material Characterization in the Terahertz Band by Selective Extraction of Sample-Induced Echo Signals. J Nondestruct Eval 34, 269 (2015). https://doi.org/10.1007/s10921-014-0269-1
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s10921-014-0269-1