3D direct laser writing using a 405 nm diode laser.

Three-dimensional (3D) direct laser writing commonly uses near-infrared femtosecond laser pulses. Here, we use a quasi-cw blue diode laser at a 405 nm wavelength. As prerequisite, we identify photoresist systems that unambiguously show nonlinear multiphoton polymerization at this excitation wavelength. Next, we obtain a diffraction-limited focus with a high-numerical-aperture objective lens (NA=1.4), which is crucial to actually benefit from the wavelength advantage. To evaluate the anticipated reduced linewidths and improved resolution, we fabricate and characterize 2D and 3D benchmark structures. Finally, we also demonstrate dip-in direct laser writing with our setup.