The fabrication of sub-100 nm feature sizes in large-scale three-dimensional (3D) geometries by two-photon polymerization requires a precise control of the polymeric reactions as well as of the intensity distribution of the ultrashort laser pulses. The authors, therefore, investigate the complex interplay of photoresist, processing parameters, and focusing optics. New types of inorganic– organic hybrid polymers are synthesized and characterized with respect to achievable structure sizes and their degree of crosslinking. For maintaining diffraction-limited focal conditions within the 3D processing region, a special hybrid optics is developed, where spatial and chromatic aberrations are compensated by a diffractive optical element. Feature sizes below 100 nm are demonstrated.

This study presents the development of post-processing steps for microfluidics fabricated with selective laser etching (SLE) in fused silica. In a first step, the SLE surface-even inner walls of microfluidic channels—can be smoothed by laser polishing. In addition, two-photon polymerization (2PP) can be used to manufacture polymer microstructures and microcomponents inside the microfluidic channels. The reduction in the surface roughness by laser polishing is a remelting process. While heating the glass surface above softening temperature, laser radiation relocates material thanks to the surface tension. With laser polishing, the RMS roughness of SLE surfaces can be reduced from 12 µm down to 3 nm for spatial wavelength λ < 400 µm. Thanks to the laser polishing, fluidic processes as well as particles in microchannels can be observed with microscopy. A manufactured microfluidic demonstrates that SLE and laser polishing can be combined successfully. By developing two-photon polymerization (2PP) processing in microchannels we aim to enable new applications with sophisticated 3D structures inside the microchannel. With 2PP, lenses with a diameter of 50 µm are processed with a form accuracy rms of 70 nm. In addition, this study demonstrates that 3D structures can be fabricated inside the microchannels manufactured with SLE. Thanks to the combination of SLE, laser polishing and 2PP, research is pioneering new applications for microfluidics made of fused silica

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Integrated passive and active devices are the key components in current and future information technology. In order to fulfill requirements in miniaturization for (integrated) optical or electronic devices, nano-scaled materials with a good compatibility to high-resolution processing techniques are needed. According to these requirements, multi-photon techniques attract much attention by providing a resolution far beyond the diffraction limit. The patterning of the inorganic-organic hybrid polymers, which are synthesized by catalytically controlled hydrolysis/polycondensation reactions, will be discussed with respect to the underlying photochemical processes. Emphasis will be on the direct writing of structures using femtosecond laser pulses, making use of two- and three-photon absorption (TPA/3PA) processes with visible or IR light, which also allows one to write arbitrary 3D structures. Due to the very sharp threshold fluence for these processes and its non-linear beh avior, features down to 100 nm can be realized by choosing a suitable combination of material formulation and patterning parameters. Voxel arrays were written, whereas the resulting voxel sizes are compared to a growth model, and the influence of radical diffusion and chain propagation is discussed. In order to determine the TPA cross-section and to estimate the role of the photoinitiator, a z-scan experiment was realized. The initiators' cross-sections will be correlated to the resulting voxel sizes