Wake Flow Field Detection of Undersea Vehicles Based on Vortex Beam Propagation

In free-space diffraction, the orbital angular momentum(OAM)of the vortex light field remains unchanged. However, in a turbulent layer, the symmetry of the OAM spectrum distribution will be broken, and the OAM will change due to the existence of a quasi-ordered structure in the flow field. In this paper, the mechanism of detecting the flow structure by using the symmetry breaking of OAM spectrum distribution was investigated. The feasibility of applying OAM of vortex light field to detect undersea vehicles was analyzed, and relevant test results were given. In addition, according to the characteristics that the total OAM of the light field also changes, the theoretical basis for identifying the characteristics of different flow fields based on OAM was elaborated through the cross-OAM matrix method. Lastly, the perception characteristics of the water medium of the vortex light field were studied. Combined with the results of numerical simulation, a technical concept for detecting undersea vehicles based on the characteristics of OAM propagation was proposed.