Impact of Polar Environmental Factors on Upward Laser Energy Transmission

Underwater laser detection and communication in polar regions have attracted increasing research interest. The stochastic roughness of the water–ice interface causes the broadening of the incident beam angle and spatial energy uncertainty, posing critical challenges for cross-medium optical transmission. This study presents a theoretical model that couples seawater volumetric scattering attenuation with rough-interface effects in upward laser transmission. The water–ice interface is discretized using Beckmann–Gaussian microfacet geometry. From this, the analytical relationship between local surface normal distributions and Fresnel reflection/transmission coefficients is derived. This enables the quantitative characterization of the process by which interface roughness modulates optical transmission. A full-link energy normalization framework is established. It encompasses normalized seawater-segment power, interface transmission efficiency, and normalized sub-ice received power. Monte Carlo photon tracing is used to simulate scattering in polar seawater and stochastic coupling at the rough interface. The results are experimentally validated. The key findings are as follows: Rising seawater temperature increases absorption but reduces scattering resulting in enhanced overall attenuation and degraded energy transfer efficiency. Interface roughness broadens the local angle-of-incidence distribution, and beyond 30°, energy transfer efficiency drops markedly. As propagation distance increases, normalized received power decreases, the beam spot diameter increases, and collimation quality deteriorates. The simulation results show strong agreement with the experimental measurements. These findings provide theoretical support for sub-ice laser signal acquisition and polarization modulation in polar environments, offering practical guidance for system design in underwater optical communication applications.