Beam wander of laser beam propagating through oceanic turbulence

The analytical expressions for beam wander of collimated and focused beam in oceanic turbulence are derived. Compared with the previously integrating ones, it can be seen that the two results are in agreement with each other exactly for the collimated and focused beam, respectively. Further, the influences of three main oceanic parameters (i.e., the rate of dissipation of mean-squared temperature χT, the rate of dissipation of kinetic energy per unit mass of seawater ɛ   and the ratio of temperature to salinity contribution to the refractive index spectrum ww) and the beam radius W0 on beam wander are investigated in the collimated and focused beam cases. The results indicate that the beam wander increases as ɛ decreases, χT increases, salinity-induced predominates and W0 decreases in mentioned above cases. In addition, based on the dimensionless quantity BW, the relation between beam wander and the long-term spot size or turbulence-induced beam spot size is investigated. In particular, to distinguish beam wander among different beam types, the relative beam wander is defined. Based on this definition, the increment of beam wander between focused and collimated beam is larger than that of arbitrary beam type (i.e., 0 < Θ0 < 1). It is beneficial to select the predominant beam type in laser propagation applications