# Polarization Transmission of Visible Light in Inhomogeneous Sea Fog Particle Environment
## 1 Introduction  
Given the changes in the environment and the range of human activities, the detection of marine environmental targets has become a new research hotspot. Polarization devices are widely used in detecting and identifying marine environmental targets [1; 2; 3]. However, sea fog particles are complex and changeable. [PERSON] pointed out that the increase in relative humidity condenses the water vapor on the sea salt to form sea fog aerosol. The refractive index of sea fog particles changes with the change in relative humidity. They change from homogeneous particles to inhomogeneous particles [4]. In the polarized light transmission channel, inhomogeneous sea fog particles' scattering effect changes polarized light's information, directly reducing the working efficiency of marine activities [5]. Therefore, we must study the effect of inhomogeneous sea fog particles on laser polarization transmission. With regard to the research on inhomogeneous particles, [PERSON] used an atomizer to simulate inhomogeneous sea fog particles in the laboratory. The researcher also used polarized lidar to measure the depolarization rate of inhomogeneous sea fog particles. The measured results were compared with the calculated results of Mie scattering, and the obtained depolarization rate of inhomogeneous sea fog particles is 0.08 \(\pm\) 0.01 [6]. [PERSON] used an inhomogeneous superellipsoid model to represent sea salt aerosols. The variation of the scattering coefficient with the wavelength when the incident wavelength is 0.2-5 \(\upmu\)m was also discussed. The results showed that when the wavelength is between 0.2 and 0.4 \(\upmu\)m, the scattering coefficient is proportional to the wavelength. Moreover, the scattering coefficient is inversely proportional to the wavelength when the wavelength is between 0.4 and 5 \(\upmu\)m [7]. In China, [PERSON] and [PERSON] used the equivalent analysis method to calculate the equivalent refractive index of the layered spherical particles. She selected the four mixing ratios (mixing ratio is the ratio of water particles and sea salt particles in the double-layer particle system) of 0.99, 0.9, 0.5, and 0.1 and the scale parameter range of 0.1-100. She also used the extinction efficiency factor to analyze the equivalence of the particles: only when the scale parameter x \(<\) 1 or x \(>\) 20, the equivalence of particles under different mixing ratios is good [8; 9]. [PERSON] used Lorenz-Mie theory to calculate the scattering matrix elements after the photons were scattered by inhomogeneous particles. Moreover, she selected four groups of the imaginary parts of the environmental refractive index, 0, 0.001, 0.01, and 0.05, and also presented the element variation of the scattering matrix and the imaginary part of the environmental refractive index. The results showed that the smaller the imaginary part of the ambient refractive index is, the larger the elements of the scattering matrix are [10]. [PERSON] used a turbidimeter to measure the scattering ability of inhomogeneous inorganic particles to light at 450, 550, and 700 nm. The author also calculated the scattering coefficient using the double-layer Mie scattering theory. The results showed that the scattering coefficient decreases with the increase in wavelength [11]. [PERSON] used the Fresnel-Huygens principle to conduct simulation calculations. Then researchers discussed the DOP distribution of inhomogeneous polarized beams traveling in ocean turbulence. They found that the power exponent and proportionality coefficient of inhomogeneous polarized beams affected the DOP [12]. Most researchers used simulation calculations in the above citations. The simulation results are parameters that can characterize polarization characteristics, such as depolarization ratio, scattering coefficient, and scattering cross-section. However, to simulate the complete process of polarized light passing through the medium, it is not enough to only calculate the polarization characteristic parameters.