## 3 Results and Discussion
Moreover, the backscattering intensity increases as the wavelength of the illuminating laser becomes longer. Results in Figure 4c show that as the particle radius increases beyond about 0.6 \(\upmu\)m, 1064 nm wavelength light will yield higher backscattering efficiencies, and therefore, this longer wavelength light will be more practical to use. These results highlight that particle size and the wavelength of the illuminating light are important parameters to consider in optimizing the backscattering intensities that will be collected by the telescope detectors. Moreover, the different backscattering intensities manifested by pure water, contaminated water and black carbon confirm that the Mle scattering intensity patterns can be used to distinguish between different scattering particles. Since the backscattering intensity depends on the wavelength of the illuminating laser light, the backscattering intensity profiles for pure water, contaminated water, and black carbon were also obtained as a function of the wavelength of the illuminating laser light for different particle radii where \(a\) = 0.1 \(\upmu\)m, 0.5 \(\upmu\)m, and 1.25 \(\upmu\)m. Figure 5a-c show the scattering intensity profiles for pure water, contaminated water, and black carbon, respectively. For pure water, backscattering is more efficient when the wavelength of the laser light is shorter. A shorter wavelength is particularly useful when the radius is 0.1 \(\upmu\)m because the backscattering intensity appears to be featureless but the intensity peaks when the wavelength is about 500 nm. For the radius of 0.5 \(\upmu\)m, the backscattering intensity shows a periodic pattern. As the radius is further increased to 1.25 \(\upmu\)m, backscattering becomes more intense, especially for short-wavelength light. For contaminated water, backscattered light from 0.1 \(\upmu\)m-radius also appears to be featureless with an intensity peak around 500 nm wavelength. When the radius is increased to 0.5 \(\upmu\)m, the intensity of backscattered light also increases, with the maximum intensity being achieved also at a shorter wavelength. These results show that when the size of the scatterer is small, shorter wavelength light is needed to elicit more efficient backscattering. For bigger scatterers, such as when the radius is 1.25 \(\upmu\)m, longer wavelength light results in a higher backscattering intensity. For both pure and contaminated water, backscattering becomes more efficient as the size of the scatterer increases. On the other hand, the intensity of backscattered light is highest for smaller black carbon particles although the scattered light still appears featureless when  
Figure 4: Back scattering intensity from (**a**) pure water, (**b**) contaminated water and (**c**) black carbon as a function of the size of the scatterer for different incident laser wavelengths. the radius is 0.1 \(\upmu\)m. When the size increases to 0.5 \(\upmu\)m, longer wavelength light results in more efficient backscattering. Interestingly, an opposite trend is observed between pure water and black carbon. Specifically, for pure water, the backscattered intensity increases as the size increases while for black carbon, the backscattered intensity decreases as the size increases. Similar to the scattering profiles as a function of size, the wavelength-dependent backscattering intensity profiles are also unique to the scattering particle regardless of the size of the particle. We note that the fluctuations observed in the backscattering efficiency plots in Figures 4 and 5 are due to the behavior of the scattering particles acting as a Mie resonator [41]. The unique scattering intensity profiles allow the identification of the scattering particle. These results illustrate the concept behind our proposed MISTS-LIDAR scheme.