Full-bandwidth, continuous, and grayscale 3D nanolithography via line-illumination temporal focusing of ultrafast lasers

Abstract: Achieving fast and continuous fabrication of large-scale complex 3D structures is key to unlocking industrial-scale adoption of two-photon lithography (TPL). Despite substantial improvement in peak optical patterning rates enabled by recent parallel exposure strategies, the practical fabrication rate of TPL for large structures remains low. This gap is primarily attributed to the mismatched bandwidth among toolpath generation, data transferring, and laser patterning, and the stop-and-go operation for part stitching etc. Here, we present a line-illumination temporal focusing TPL (Line-TF TPL) solution that, for the first time, demonstrates true continuous 3D nanolithography with full-bandwidth data streaming, grayscale voxel tuning, and cost-effective large-scale fabrication capability. To achieve the goal, we use a digital micromirror device (DMD) to temporally focus femtosecond laser pulses into a programmable line with enhanced 3D resolution, pixel-level grayscale control, and a high-refresh rate (>10 kHz), realizing continuous fabrication at a hardware-limited maximum rate. Specifically, we fabricated centimeter-scale 3D structures with sub-diffraction features down to 75 nm laterally and 99 nm axially. Our method eliminates stitching defects by continuous scanning and grayscale stitching; and provides real-time pattern streaming at a bandwidth that is one order of magnitude higher than previous TPL systems. The line-scanning strategy also substantially lowers the pulse-energy requirement, hence the cost for parallel TPL; and maximizes the machine uptime through continuous operation, both of which are critical metrics for industrialization. Finally, we demonstrated centimeter-scale artworks, fine 3D features, and complex miniaturized optics, revealing the Line-TF TPL's large-scale application potential in photonic packaging, metamaterial discovery, and biomedicine.