Time-dependent volumetric printing of precision lenses through dynamic laser writing

Abstract The position-dependent feature in current vat photopolymerization-based additive manufacturing leads to challenges in controlling the dimensional accuracy of printed components. To overcome this intrinsic limitation, we propose a time-dependent dynamic laser writing (DLW) approach for the precise volumetric printing of complex-shaped lenses. In the DLW-based volumetric printing, the formed surface is generated by accumulating the material growth functions (MGFs) on the scanning path, where the MGF is created by the laser direct irradiation with controlled energy doses. Benefiting from the stability of MGFs and the process homogenization, the DLW is less sensitive to process errors when compared to current vat photopolymerization-based additive manufacturing techniques. Furthermore, the continuous scanning leads to the naturally ultra-smooth feature of the printed surfaces. As a demonstration, a millimeter-scale spherical lens was printed in 5.67 minutes, achieving a three-dimensional form error of 0.135 $\mu$m (RMS) and a surface roughness of 0.31 nm (RMS). The printing demonstrated comparable efficiency while achieving form errors an order of magnitude smaller than those of state-of-the-art continuous layer-wise and volumetric printing methods. In addition, polymer lens arrays, freeform polymer lenses, and fused silica lenses were successfully printed, demonstrating promise for advancing the state-of-the-art in 3-D printing of precision lenses.