Two-color 3D printing for reduction in femtosecond laser printing power

Two-photon polymerization (TPP) has emerged as a favored advanced manufacturing tool for creating complex 3D structures in the sub-micron regime. However, the widescale implementation of this technique is limited partly due to the cost of a high-power femtosecond laser. In this work, a method is proposed to reduce the femtosecond laser 3D printing power by as much as 50% using a combination of two-photon absorption from an 800 nm femtosecond laser and single photon absorption from a 532 nm nanosecond laser. The underlying photochemical process is explained with modeling of the photopolymerization reaction. The results show that incorporating single-photon absorption from a visible wavelength laser efficiently reduces inhibitor concentration, resulting in a decreased requirement for femtosecond laser power. The radical to macroradical conversion is dominated by the reduction in oxygen concentration, while the reduction in photoinitiator concentration limits the threshold power reduction of the femtosecond laser.