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Description
This article summarizes part of the research related to the properties of the structured laser beam (SLB). The SLB has the potential to be used as a long reference line for alignment applications. This is due to SLB features such as a very clear spot in the center of the beam, a sharp demarcation of the central spot, low divergence of the central spot (practically measured value 10 μrad), theoretically infinite range (tested at 200 m), etc. 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 generalizing the diffraction integral was developed to trace accurately any optical beam in a non homogeneous environment. This solution offers in principle a better accuracy than the Eikonal equation used for ray tracing. The detection methods to evaluate the center position of the optical beam work with 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 illustrates the differences between these two descriptions of trajectories and identifies conditions under which these differences are negligible in an inhomogeneous environment. Furthermore, the influences of different types of environmental non homogeneities on the SLB trajectory are discussed.
