Dynamic Multi-Focus 3D Laser Nanoprinting Based on Two-Step Absorption and Computational Holography

Abstract

Two-step-absorption 3D laser nanoprinting allows for using compact and low-cost continuous-wave (cw) lasers. Therefore, it is an attractive alternative to established state-of-the-art multi-photon-absorption 3D laser nanoprinting. Additionally, low single-focus polymerization-threshold laser powers pave the way for multi-focus parallelization approaches while still using compact cw laser sources. Parallelization is further encouraged by the fact that single-focus scanning velocities are inherently limited by the intermediate-state lifetime of the photoresist system used. Herein, a 3D nanoprinting setup that combines an established two-step-absorption photoresist system with a dynamic multi-focus approach based on binary holography and a digital micromirror device (DMD) is presented. The generated holographic patterns allow for combined beam-splitting and beam-steering as well as for the control of each focus’ individual intensity. Therefore, one obtains a versatile printing approach, enabling a dynamic change of the number of foci for each pattern, based on the structure to be printed. With this setup, the printing of 3D microstructures using up to 31 laser foci in parallel at a print rate of up to $61500\mathrm{voxels}{s}^{-1}$ is achieved. Additionally, the capabilities and limits of the chosen approach are compared with rate-equation calculations.