Two-photon polymerization with a 780 nm monolithic diode laser

Abstract

Two-Photon Polymerization (2PP) is a high-precision additive manufacturing technique enabling the creation of intricate three-dimensional structures with sub-100 nm resolution. By focusing an ultrashort laser pulse within a photosensitive material, the nonlinear process of two-photon absorption is initiated in the vicinity of the laser focus. This results in the curing of a small volume with a size below the diffraction limit. However, the widespread adoption of 2PP in research and industry has been hindered by its expensive experimental setup. The largest cost factor in the experimental setup is the laser source, as an ultrashort pulsed laser system is required. Conventionally, fiber lasers or titanium-doped sapphire lasers are used. In contrast, the use of a diode laser could significantly reduce the cost of the laser source. In this work, we report the first structures fabricated by 2PP using a newly developed monolithically mode-locked diode laser. The diode laser has a pulse width of 7 ps, a peak power of 34 W , a repetition rate of 6.6 GHz, and a center wavelength of 780 nm. The center wavelength of 780 nm is crucial for optimal absorption of the laser radiation by the photoresists commonly used in 2PP. As a result, single lines could be fabricated with 2PP in a single scan, enabling the fabrication of three-dimensional structures in a reasonable process time. The process and the laser parameters were optimized and compared with respect to the highest possible scan speed.