title: Three-dimensional micro-/nano-structuring via direct write polymerization with picosecond laser pulses.
abstract: We demonstrate capability to structure photo-polymers with sub-wavelength resolution, ∼200-500 nm, and retrieve three-dimensional (3D) structures using a picosecond laser exposure. This alternative to commonly used ultra-short femtosecond lasers extends accessibility of 3D direct write. A popular hybrid sol-gel resist SZ2080 was used for quantitative determination of structuring resolution at 1064 nm and 532 nm wavelengths and for pulses of 8-25 ps duration at the repetition rates of 0.2-1 MHz. Systematic study of feature size dependence of 3D suspended nano-rods shows that linear power dependence of photopolymerization on the dose-per-pulse becomes dominant at higher repetition rates (≥0.5 MHz) while the two-photon nonlinear absorption is still distinguishable at rates lower than 0.2 MHz and shorter pulses (≤8 ps). Thermal accumulation defines polymerization when cooling time of the focal volume is larger than separation between pulses. Photopolymerization and its scaling mechanisms, quality, and fidelity at tight focusing of fs-, ps-, and cw-laser radiation are revealed and explained. 3D scaffolds for biomedicine and microlenses for optical applications are fabricated by the ps-laser direct write.
authors: Laser Nanophotonics Group, Laser Research Center, Department of Quantum Electronics, Physics Faculty, Vilnius University, Sauletekio ave. 10, LT-10223 Vilnius, Lithuania. mangirdas.malinauskas@ff.vu.lt
authors: Mangirdas
authors: M
authors: Malinauskas
authors: Paulius
authors: P
authors: Danilevičius
authors: Saulius
authors: S
authors: Juodkazis