24 October 2017 Nonlinear changes of chlorophyll-a fluorescence with laser induced saturation
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Proceedings Volume 10462, AOPC 2017: Optical Sensing and Imaging Technology and Applications; 104621C (2017) https://doi.org/10.1117/12.2283458
Event: Applied Optics and Photonics China (AOPC2017), 2017, Beijing, China
Laser induced fluorescence (LIF) is a common technique for measuring chlorophyll-a (Chl-a) concentration in water, and is able to obtain profile distribution. The natural water body is a turbid media for laser transmission, resulting in a great attenuation of luminance in a short distance. Increasing laser intensity is often considered an effective way to probe deeper. However, it has been found that there is a non-linear relationship between fluorescence intensity of Chl-a solution and laser energy which may causes laser-induced saturation of fluorescence with measurement conditions unchanged. Thus, the saturation effects of Chl-a fluorescence at 685 nm were studied at two aspects, namely, Chl-a concentration and the intensity of excitation pulse. In the experiment, several concentrations of Chl-a solution were measured by 355 nm laser. For a fixed Chl-a concentration, the intensity of fluorescence gradually becomes to worse following the intensity of excitation pulse raised, while the ratios of Raman intensity of water to pulse intensity correspond to a good linear relationship. On the other hand, with different energy densities of excitation laser, the variations of Chl-a fluorescence intensity were analyzed by non-linear curve fitting. For higher Chl-a concentration, the lower threshold value of excitation intensity can lead to the nonlinearity of induced fluorescence intensity versus laser intensity. Here, the nonlinear changes of Chl-a fluorescence with saturated excitation are studied for supporting the measurement of oceanographic fluorescence by LIF and correctly estimating chlorophyll concentrations.
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Xiao-long Li, Xiao-long Li, Fei Yu, Fei Yu, Yong-hua Chen, Yong-hua Chen, Jing-bo Jiang, Jing-bo Jiang, Qing-kui Liu, Qing-kui Liu, Yan He, Yan He, Wei-biao Chen, Wei-biao Chen, } "Nonlinear changes of chlorophyll-a fluorescence with laser induced saturation", Proc. SPIE 10462, AOPC 2017: Optical Sensing and Imaging Technology and Applications, 104621C (24 October 2017); doi: 10.1117/12.2283458; https://doi.org/10.1117/12.2283458

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