Simultaneous Measurement of Polarization and Excitation-Emission Spectrum of Suspended Particles in Water

The detection of suspended single particles (SSPs) in water is a crucial element for monitoring water ecosystems. Although there are a variety of sensory methods, it is still an unrealized goal to combine multi-wavelength polarized light scattering and fluorescence excitation-emission matrix(EEM) to characterize and classify SSP in water,which can deeply characterize and classify SSPs with different properties. In this paper, we propose an efficient optical method that can simultaneously obtain the SSP's Stokes parameters of four wavelengths and the fluorescence excitation-emission matrix (EEM) within 125 ns at 120 degree scattering angle in water. We use Mie scattering simulation to validate our method and obtain the optimal parameters for the experiments. We demonstrate the high performance of our method in terms of sensitivity and accuracy through experiments involving microalgae, microplastics and sediments, as well as control experiments under different illumination conditions and classification experiments of harmful microalgae by using a multi-layer perceptron (MLP) to classify underwater suspended particles and harmful microalgae based on our method, and show that our method achieves better results than using single-wavelength light. Our method paves the way for the detection of SSPs and polarization research in marine science.