Model and Design of Incoherently and Geometrically Combined Laser Beams for Optimum Overlap and Power*

Laser beam combining has attracted much attention recently for free space laser communication and high power laser applications. Most of the methods used required additional components in the beam’s path such as beam splitters, polarizers, diffraction gratings, or fiber optics combining. This reduces the power and affects the combined beam profile. In this study, we present a model for incoherently combining three laser beams using a system of two optical lenses to allow for longer overlap distance between the beams and minimum power loss. We have developed a ray tracing model based on ABCD theory and finite elements method to conduct ray tracing and spatially combine the three incoherent laser beams. The initial horizontal spread of the three beams was 21.4 mm with each beam measuring 11.2 mm in waist. Using our optimized system, we were able to combine 98% of the three beams at a distance of 9 m. The overlap of the combined beams only changed by 2% over a long distance range of 4 m (from 7 m to 11 m). This result did not require any additional optical adjustments or components. The method is currently in the process of implementation experimentally indoors under laboratory conditions and will be extended to about 1 km in outdoors environment.