Nanoprocessing using near-infrared sub-15 femtosecond laser microscopes

Tightly focused 85 MHz repetition rate sub-15 femtosecond pulsed laser light of a central wavelength at 800 nm facilitates submicron and nanoscale processing of a large variety of materials. Three-dimensional polymer structures were generated by two-photon lithography and applied as cell culture substrates. Conically shaped capillaries with sub-100 nm edges were produced in SU-8 for electrospray ionization. Indium tin oxide (ITO) nanowires resulted from recrystallization on sub-ablation threshold exposure and subsequent etching in hydrochloric acid. Nanowires on glass were applied as gas sensors, whereas free-standing nanowires acted as resonators with resonance frequencies in the megahertz range. Laser-induced periodic surface structures (LIPSS) were generated on crystalline silicon surfaces and in thin ITO films at periodicities below 200 nm. Periodic nanocuts produced on-chip increased the effective area of ITO multi-electrode arrays. ITO thin-film electrodes for liquid crystal (LC) applications were patterned by sub-15 fs LIPSS in order to facilitate LC alignment. The properties of the structures and the performance of the devices were investigated using the finite-element method.