Hologram design framework: reconstruction area of volumetric beam shaping

We developed a design framework for computer-generated holograms (CGHs) implemented with a spatial light modulator (SLM) for volumetric beam shaping. This approach enables shaping the laser beam in both the transverse and axial directions, meeting industry requirements for quality and throughput while also facilitating further improvements in functionality. The design framework encompasses CGH optimization algorithms, analog and digital optical parameters, evaluation functions, software, and the target beam, all of which are defined according to the processing requirements. Our objective is to propose a method for determining an acceptable axial reconstruction area and to incorporate it into a design framework. We found that normalizing the beam profile evaluation curve collapses it onto a single curve. The curve depended on the power of the CGH, which is an inverse relation to the number of pixels of the SLM. As a result, the axial reconstruction area can be determined consistently and systematically. The results are expected to be applied to diverse industrial applications, including straight-through holes with high aspect ratios, micro-patterning, grooving of multilayer materials, and even dicing of micro-devices with higher-order structures.