Aberration-free large-area stitch-free 3D nano-printing based on binary holography

Abstract

Direct laser writing (DLW) has been widely used in a variety of engineering and research applications. However, the fabrication of complex and robust three-dimensional (3D) structures at submicron-level resolution by DLW is still largely limited by the laser focus quality, i.e., point spread function (PSF), laser dose, precision of mechanical scanners, and printing trajectory. In this work, we present a two-photon polymerization (TPP)-based DLW system based on a digital micromirror device (DMD) and binary holography to realize aberration-free large-area stitch-free 3D printing as well as 3D random-access scanning. First, the binary holograms, which control the amplitude, phase, and position of the laser focus, are optimized by the sensorless adaptive optics algorithm to correct the distorted wavefront in the DMD work field. Next, the DMD is synchronized to a continuously moving sample stage to eliminate stitching errors, i.e., the sample positioner simultaneously moves with the scanning focus until the structure is completed. We have fabricated large-area complex 3D structures, e.g., metamaterial structures, and micro-lenses, and 2D gray level diffractive optical elements (DOEs) with better than 100 nm resolution and optimal scanning trajectories. Notably, the variation of the scanning trajectory, laser power (dose), and voxel sizes can be realized without affecting the scanning speed, i.e., 22.7 kHz, which is equivalent to the DMD pattern rate.