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Significant performance improvement of modern laser technologies such as welding, additive manufacturing, brazing, cladding, sheet metal cutting, based on the use of multi-kW multimode fiber lasers, fiber-coupled solid-state and diode lasers, can be improved using beam shaping optics providing optimal energy distribution by splitting the laser beam into several beamlets creating by further focusing separate multiple spots in the working plane and variable sharing energy between these spots. Various multi-spot patterns, such as square, line, rhombus, consisting of 4 or 9 separate spots, allow eliminating or reducing spatter, realizing optimum temperature distribution in the melt pool and stabilizing the processes in welding of tailored blanks, copper and aluminium parts in the production of batteries, zinc coated steel, cladding. Multimode lasers are characterized by low spatial coherence (large BPP or M² values), therefore the most reliable optical approach to control the intensity distribution is imaging the fiber end with a collimator and a focusing objective. The proposed multi-spot beam shaping method presents a combination of fiber end imaging and geometrical separation of focused spots perpendicular to the optical axis, thus creating a compound working spot, called as quattroXX-spot or peaXXus-spot, as a combination of several spots. Varying the energy portions in separate spots and the distances between them make it possible to optimize for a particular application common intensity distribution of the compound spot. To ensure reliable operation with multi-kW lasers and to avoid optics damage the multi-focus optical devices are designed as refractive elements with smooth optical surfaces made of optical materials self-compensating thermo-optical effects that provides insignificant thermal lensing and, hence, negligible thermal focus shift and spherical aberration. The paper presents the proposed multi-spot optics, shows intensity profile measurements and application results.
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