Propagation characteristic of OAM blue-green laser in seawater

The blue-green laser, which is attenuated less in water, are of potential applications in the deep seawater communication. The Orbital Angular Momentum (OAM) as a new degree of freedom with characteristic of unlimited topological charge, is expected to extensive improve the capacity of blue-green laser communication. In seawater channel the turbulence is the main factor to influence laser transmission, thus, it is important to research the effect of seawater turbulence on OAM blue-green laser. In this paper, based on power spectrum method the phase screen effected by turbulence is studied, and the transmission model for OAM LG laser in the presence of seawater turbulence is established. For typical wavelength of 532 nm, the received laser power and phase is analyzed with different transmitted distance and beam waist. Mathematical simulation shows that, the smaller the beam waist is, the better the OAM spiral phase matins and the stronger the received laser power is, since the turbulence influence is less, which means the smaller beam waist obtains obvious advantages. The results can benefit the transmission characteristic analysis and modulation for underwater blue-green laser channel research and provide foundation for system optimum design.