  The cross-spectral density of coherent Gaussian vortex beams propagating
through weak oceanic turbulence is derived from extended Huygens-Fresnel
principle and Nikishov spectrum. The evolution of a coherent superposition
field composed of dual Gaussian vortex beams with $+1$ and $-1$ topological
charges respectively through weak oceanic turbulence is investigated in z plane
and y plane. It is shown that the non-zero separation distance of two beams in
x direction enhances the oceanic turbulence effect on interference light field.
The variation of intensity distribution in z plane and on the central axis of
two beams in y plane are both related to the strength of oceanic turbulence,
separation distance, propagation distance and waist width. The extra
fluctuation of the intensity on the central axis of two beams in y plane leads
to high sensitivity of oceanic turbulence. This characteristic has potential
application in non-contact optical tomography of oceanic turbulence strength
along the beam propagation path by lateral scattering intensity.

Optics