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Proceedings Paper

Terahertz frequency spectrum characterization of coherent heterodyne time-domain spectrometer
Author(s): Ji Zhao; Liang-liang Zhang; Yi-man Luo; Tong Wu; Cunlin Zhang; Yue-jin Zhao
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Paper Abstract

Terahertz wave which can provide innovative sensing and imaging techniques can obtain spectroscopic information unavailable at other wavelengths. The terahertz air-biased-coherent-detection (ABCD) method can achieve the third-order nonlinear susceptibility tensor to produce field-induced optical second harmonic photons. Therefore, the intense terahertz wave generated and detected by the laser-induced air plasma provides a promising ultra-broadband terahertz source and sensor for spectroscopy and imaging technique. Aiming at that purpose, an understanding of the frequency spectrum characterization of terahertz pulse is crucial. In this work, we investigated the variation of the THz pulse bandwidth measured through the third harmonic generation using the coherent detection scheme, by increasing the optical probe pulse power and biased electric field. A bandwidth broadening of the measured THz pulse is observed by increasing either the probe pulse power or the bias voltage strength. We speculate that a pulse shape change of the probe beam and a saturation effect during the second-harmonic generation might cause the bandwidth broaden with probe power. To further investigate the mechanism, we fixed the power of probe laser at 150mW and changed the bias voltage. The results show that the frequency spectrum width becomes wider gradually with the increasing of the bias voltage. A theoretical explaination shows that the bandwidth broadening with bias field might be introduced by a pulse shape change of the bias field induced second harmonic wave. This study reveals that we can control THz intensity and bandwidth by changing probe power and bias voltage in the ABCD system.

Paper Details

Date Published: 31 December 2013
PDF: 6 pages
Proc. SPIE 9042, 2013 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments, 904210 (31 December 2013); doi: 10.1117/12.2036332
Show Author Affiliations
Ji Zhao, Beijing Institute of Technology (China)
Capital Normal Univ. (China)
Liang-liang Zhang, Capital Normal Univ. (China)
Yi-man Luo, Capital Normal Univ. (China)
Tong Wu, Capital Normal Univ. (China)
Cunlin Zhang, Capital Normal Univ. (China)
Yue-jin Zhao, Beijing Institute of Technology (China)


Published in SPIE Proceedings Vol. 9042:
2013 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments
Yongtian Wang; Xiaocong Yuan; Yunlong Sheng; Kimio Tatsuno, Editor(s)

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