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Proceedings Paper

Water vapor detecting using high-Q microcavity
Author(s): Yingzhan Yan; Shubin Yan; Zhe Ji; Jijun Xiong
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Paper Abstract

The target of this paper is to design a novel water-vapor sensor used in humidity transducer system based on high-quality factor (Q) spherical microcavities, which at present obtained the highest Q value induced by surface tension. Sensitive mechanics and its high sensitivity are discussed according to optical loss sensitization to coupling system composed of a microsphere cavity and a tapered fiber. After that, fabrication methods of master parts of the sensor in our lab are introduced. Additionally, a sensing structure composed of a gas-chamber and a vacuum-chamber is also designed. According to water absorption band, telecom band around 1550nm is used to pump the microsphere optical mode. In a vacuum environment, a transmitted spectrum is obtained through output end, revealing some information about the core system including the size of the microcavity and the optical loss of the regime. However, when the core system is placed in a water vapor environment, the transmitted spectrum will change due to extra optical loss induced by water molecules absorption, behaving as spectral shift, free spectrum range (FSR) or line width broadening. Contrasting and analyzing two different spectrums in the two situations, the gas concentration can be deduced. Indispensable experiments were also carried out, showing that, the two spectrums are different from resonance hump, formant strength and formant line width. Even an ultra low water vapor concentration induced a measurable output signal, ensuring a high detecting sensitivity. Certainly, the analyted vapor should not only be water vapor. This kind of sensitive mechanics is versatile. Changing the pumping light corresponding to the analyted absorption band, we are able to detect a series of vapor.

Paper Details

Date Published: 23 November 2009
PDF: 9 pages
Proc. SPIE 7508, 2009 International Conference on Optical Instruments and Technology: Advanced Sensor Technologies and Applications, 75080A (23 November 2009); doi: 10.1117/12.837894
Show Author Affiliations
Yingzhan Yan, North Univ. Of China (China)
Shubin Yan, North Univ. Of China (China)
Zhe Ji, North Univ. Of China (China)
Jijun Xiong, North Univ. Of China (China)

Published in SPIE Proceedings Vol. 7508:
2009 International Conference on Optical Instruments and Technology: Advanced Sensor Technologies and Applications
YanBiao Liao; Anbo Wang; Tingyun Wang; Yukihiro Ishii, Editor(s)

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