Femtosecond laser nanoprocessing using near-infrared nanojoule pulses at MHz repetition frequency

Sub-80nm, sub-wavelength multiphoton nanoprocessing of silicon wafers as well as 3D maskless lithography by two two-photon polymerization in combination with five-dimensional (x,y,z, λ, τ) multiphoton analysis have been performed with the compact near infrared MHz femtosecond laser galvoscanning microscope FemtoCut (JenLab GmbH) as well as a modified ZEISS LSM510-NLO system. Laser excitation radiation was provided by a tuneable turnkey, one-box Chameleon as well as a MaiTai Ti:sapphire laser oscillator. Nanostructuring of silicon wafers with oil immersion objectives was based on NIR laser-induced periodic surface structures (LIPPS) likely due to selforganization processes. For the first time, periodic 70nm nanogrooves have been generated in wafers which is one order below the 800 nm laser wavelength by multiphoton phenomena at TW/cm2 transient intensities and low sub-3nJ pulse energies. Three-dimensional two-photon polymerization in SU-8 photoresists at GW/cm2 allowed rapid prototyping with sub-200nm precision. The same intensities have been used to image endogenous and exogenous fluorophores in a variety of materials for target finding and the evaluation of the nanoprocessing procedures.