Femtosecond laser-induced two-photon photopolymerization for structuring of micro-optical and photonic devices

Light initiated liquid polymer quasi-instant solidification is attractive for its ultra precise spatial and temporal control of the reaction. Here we present femtosecond laser induced two-photon photopolymerization for structuring of microoptical and sample photonic devices. Due to nonlinear phenomena the fabrication resolution is not restricted to diffraction limit for the applied laser excitation wavelength but determined by the exposure dose. Furthermore, pinpoint structuring enables one to produce 3D structures of any form out of photopolymer. The smallest structural elements voxels of 200 nm lateral dimensions can be achieved reproducibly by using high numerical aperture optics. Axial resolution which is fundamentally few times worse than lateral can be controlled in few hundred nanometers precision by forming polymeric pad as an additional structure. In our work we applied commercially available and widely used hybrid zirconium-silicon based hybrid sol-gel material ORMOSIL (SZ2080) and an acrylate based AKRE37 photopolymer. Arrays of custom parameters spherical microlenses for microscopy applications have been fabricated. Their surface roughness, focal distance and imaging quality were tested. 3D custom form woodpile structures with submicron period and chain-mail structure were made as a sample photonic bandgap structures. Finally, we show some structures produced out of fluorescent dyes rhodamine 6G doped photopolymer.