Femtosecond visible light induced two-photon photopolymerization for 3D micro/nanostructuring in photoresists and photopolymers

Abstract

Laser two-photon polymerization (LTPP) has been widely reported as a tool for three-dimensional micro/nanofabrication. Femtosecond lasers are employed to form nanostructures in photosensitive resins with subwavelength resolution. We demonstrate high throughput large scanning area LTPP system based on linear motor driven stages combined with Yb:KGW high repetition rate (312.5 kHz) amplified laser as irradiation source (515 nm second harmonic’s wavelength). Femtosecond green light can be focused to a smaller diffraction limited spot and provides higher structuring resolution comparing to commonly used Ti:sapphire lasers (operating at NIR wavelengths) used for LTPP. Additionally, shorter irradiation wavelength enables to process more of widely used photosensitive materials. The system capacitates production of nanostructures having 200 nm lateral resolution with high repeatability. By modifying focusing optics there is a possibility to scale up the fabrication: reduction of resolution results in shortening of fabrication time. The system enables formation of 3D structures with size varying from tens of microns to tens of millimetres. Most of the materials commonly used for photopolymerization technology (various blends of acrylates, hybrid organic–inorganic materials, and epoxy resins) are well suitable for processing with the constructed LTPP system. Keywords: two-photon absorption, laser processing, photopolymerization, micro/nanofabrication, three-dimensional structures, tissue engineering