Structured laser beam in non-homogeneous environment

This article summarizes part of the research related to the structured laser beam (SLB) properties focused on align- ment. The SLB has the potential to be used as a reference line. This is due to SLB features such as a very clear spot in the center of the beam, a sharp boundary of the central spot, low divergence of the central spot (practically mea- sured value 10 µrad) and theoretically infinite range (tested over several hundred meters). However, the environment (the non-homogeneous distribution of the refractive index) affects the trajectory of the SLB, which is then a general curve. A new approach based on numerical simulations was used to investigate this phenomenon. A method gen- eralizing the diffraction integral was developed to trace ac- curately any optical beam in a non-homogeneous environ- ment. This solution offers in principle a better accuracy than the Eikonal equation used for ray tracing because it allows evaluating the position of the optical beam center with methods based on the analysis of the optical intensity transverse distribution. The propagation of the complex amplitude in the longitudinal direction can generally not be described by the Eikonal equation, but the generalized diffraction integral attains this goal. The article compares the trajectories of a SLB calculated using both the Eikonal equation and the generalized diffraction integral. It de- scribes the differences between these two approaches and identifies conditions under which these differences are neg- ligible in an inhomogeneous environment. Furthermore, the influences of different types of environmental non ho- mogeneities on the SLB trajectory are discussed.