Design and prototyping of beam shapers to generate circular or square top-hat beams of different size for additive manufacturing applications

Many industrial and research applications benefit from laser beam profiles which are non-Gaussian but rather tailored to that specific application. For example, shaping the beam profile and footprint holds great potential for beam delivery in laser-assisted manufacturing processes. In particular, top hat beam profiles of different shapes and size would enable speeding up additive manufacturing while increasing the resolution of the 3D printed parts. In this paper, we present the design of different beam shapers for high power CO₂ lasers used in laser sintering, which are able to generate respectively square and circular top hat beam profiles. The size of the spot is controlled by using additional lenses to reduce or enlarge the beam size as necessary after the beam shaping optics. A spot size of 0.5 mm or 5 mm diameter can be achieved by switching between different lenses and adjust the distances accordingly. The designed beam shaping optics were subsequently fabricated in-house using ultra-precision diamond tooling in zinc sulfide material which is tolerant to high laser power and transparent at a wavelength of 10.6 μm. This beam shaping optics can form the basis for dynamic beam shaping in which the spot size, spot shape and/or intensity profile can be actively controlled by moving the optical components in the laser beam path.