9 November 2010 Research on the characteristics of hydrogel coated long period gratings
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In this paper, the characteristics of the LPG with thin film coating are analyzed theoretically by using the optical couple-mode theory and cylindrical four-layer waveguide model. The influences of the refractive index and thickness of film overlay on the sensitivity of LPG are analyzed in detail. By choosing properly the thickness and refractive index of the thin-film overlay, the sensitivity of the LPG can be enhanced significantly. In order to verify the theoretical analysis and enhance the sensitivity of LPG to humidity, hydrogel is chosen as coating material. The characteristics on the hydrogel coated long period grating are investigated experimentally. The transmission spectral response of hydrogel coated LPG to relative humidity is measured. It shows that the resonant wavelength and the amplitude of attenuation bands are high sensitive to relative humidity when RH is above 50%RH.
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Xiujuan Yu, Xiujuan Yu, Min Zhang, Min Zhang, Yanbiao Liao, Yanbiao Liao, } "Research on the characteristics of hydrogel coated long period gratings", Proc. SPIE 7853, Advanced Sensor Systems and Applications IV, 78533K (9 November 2010); doi: 10.1117/12.871555; https://doi.org/10.1117/12.871555

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