11 October 2010 Research on time-resolved terahertz spectroscopy
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We have built a set of terahertz time-domain spectroscopy system using electro-optic crystals. Conventional terahertz time-domain spectroscopy based on Fourier-transform for spectra analysis, which mixes the frequency components of the entire temporal terahertz waveform in one frequency domain; therefore, it yields different terahertz spectra from a same terahertz pulse with different scanning lengths. We introduce a new technique for the joint time-frequency analysis of terahertz time-domain spectroscopy based on wavelet-transform technique. With this technique, the frequency components in different time locations are clearly exhibited on a two-dimensional plane; therefore, the noise in the pulse tail cannot affect the frequency in the main pulse. This technique clearly separates the frequency of terahertz from that of its echo in the time domain; therefore, the interference spectrum occur in Fourier-transform is naturally removed. By varying the shape of analysis wavelet, high time resolution and high frequency resolution are easily obtained. The absorption coefficients of envelope, plastic, foam and cotton have been measured with the wavelet technique.
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Yuqiang Deng, Qing Sun, Feng Liu, Changlei Wang, Qirong Xing, "Research on time-resolved terahertz spectroscopy", Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 76560T (11 October 2010); doi: 10.1117/12.863981; https://doi.org/10.1117/12.863981

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