High power and small spot fiber coupling system for pump sources based on symmetric stepped prisms

With the development of solid-state lasers and fiber lasers, the output power and spot size of the pump source of semiconductor lasers have higher requirements. A compact output high power and small spot fiber coupling system based on symmetric stepped prisms for laser pumps is proposed to improve and equalize the beam quality in both directions by total reflection of symmetric stepped prisms as well as a set of quadrilateral parallel plates. The proposed shaping prism can be designed without considering the refractive index of the material and does not require the use of an optical element stack., which reduces the number of optical components used and enhances the optical coupling efficiency. The method combines eight laser bars stacked vertically into a target fiber with a 200 μm core diameter and a 0.22 numerical aperture. The final output power of 550.4 W is obtained at the output end of the optical fiber through simulation, and the optical-to-optical conversion efficiency of the whole designed system is 86%, which meets new application requirements.