Addressing unstable stratified oceanic turbulence, this paper develops a composite stratified oceanic turbulent phase screen model using power spectrum inversion, which fully accounts for the coupled effects of turbulence diffusion, absorption, and scattering. We investigate the intensity and phase evolution of Perfect Vortex Beams (PVBs) after propagation, comprehensively analyzing scintillation index variations across different topological charges, propagation distances, and turbulence parameters, alongside the Bit Error Rate (BER) of OOK-modulated underwater wireless optical communication (UWOC) systems. To mitigate turbulence-induced fading, multi-aperture reception is introduced, with performance gains evaluated as a function of aperture diameter D and number N. Results show that at propagation distances exceeding 55 m, higher-order PVBs exhibit significantly lower scintillation indices than lower-order ones due to their superior topological stability. Scintillation and BER intensify with decreasing kinetic energy dissipation or increasing mean-square temperature dissipation and temperature–salinity balance parameters, with temperature dissipation being the dominant factor. Multi-aperture reception effectively smooths channel fading by leveraging intensity fluctuation decorrelation. The equivalent scintillation index decreases significantly with increasing N and D, though marginal gains diminish as N grows. In weak turbulence, increasing D from 0.02 m to 0.06 m for a single aperture reduces the scintillation index by 46.3%; when the aperture number increases from N = 1 to 2, the equivalent scintillation index drops by an average of approximately 42%, confirming that N = 4~6 provides an optimal trade-off between complexity and performance. In strong turbulence, multi-aperture reception efficiency is higher; the first three apertures contribute approximately 65% of the total gain, and the marginal gain inflection point shifts from N ≈ 7 to N ≈ 5. This study provides a theoretical basis for designing robust UWOC systems.

Laser-induced acoustic communication is a highly adaptable cross-medium technique that combines the advantages of optical transmission through air and acoustic transmission underwater. However, poor signal stability at high repetition frequencies currently hinders its widespread application. To address this, this paper proposes an innovative scanning focal-point method to enhance stability. Traditional methods such as beam scanning, focus control, and distributed interaction are primarily aimed at enhancing sound pressure in a specific direction, achieving near-field/far-field focusing, or improving the signal-to-noise ratio through coherent synthesis of ultrasonic intensity. In contrast, the method proposed in this paper is intended to avoid the interference of droplets and vapor generated by single-point breakdown under high repetition frequencies, which would otherwise degrade the laser-acoustic conversion efficiency. It is therefore an active defense strategy specifically targeting the stability of laser-induced acoustic communication. First, optical simulation software was used to analyze the effects of surface ripples and bubbles on focal spot displacement and size. Next, a single-pulse experimental system was developed to measure the range and duration of surface depressions caused by optical breakdown. Finally, a scanning focal-point system was constructed for comparative experiments, with results recorded via hydrophones and high-speed cameras. The maximum laser-induced acoustic signal generated by the scanning focal-point method is 7.4 times that produced by single-point breakdown. The experimental results demonstrate that the scanning focal-point method can effectively avoid the influence of water surface disturbance and steam on the optoacoustic conversion efficiency and significantly improve the amplitude and stability of the laser-induced acoustic signal.

Wireless optical communication technology offers advantages, such as high-data transmission rates, confidentiality, and robust anti-interception capabilities, making it highly promising for cross-sea–air interface communication applications. However, to our knowledge, no studies have been conducted on the spatial transmission efficiency of light after it passes through ocean waves. To address this issue, a seawater-wave–atmosphere model based on Gerstner waves was constructed. Using the Monte Carlo method, the optical power distributions of the laser light passing through the sea–air interface at the first- and second-level sea scales were simulated. The optimal positions for deploying one to three receiving optical systems were analyzed, and a laser communication receiving system was designed. Furthermore, simulations were conducted to determine the optical transmission efficiency of the designed optical receiver system. At the first-level sea scale, the optimal position for a single-point detector was (0°, ±5.61°), whereas those for the two detectors were (0°, ±5.61°) and (0°, ±5.68°). At the second-level sea scale, the optimal position for a single-point detector was (0°, ±3.17°), and the optimal positions for the two detectors were (0°, ±3.1°) and (0°, ±2.98°). Under the designed conditions, the optical transmission efficiency for a single detector at the first- and second-level sea scales was 0.74–0.88%, respectively, while it was 0.79–1.09% in the two-detector case. At the second-level sea scale, the optical transmission efficiency for a single detector was 0.37–2.09% and 0.50–1.97% in the two-detector case.