Direct laser writing of metal nanostructures from the gas phase by two-photon-absorption process

A new approach for the generation of three-dimensional metal nanostructures, based on two-photon-absorption (TPA) of fs-laser radiation on silver-precursor molecules in the gas phase, is introduced. For that, a mode-locked fs-laser of 800 nm central wavelength and a pulse duration of 10 fs at a frequency of 76 MHz is used. The deposition process is performed in a vacuum chamber, allowing for evaporating a liquid organometallic silver-precursor under controlled temperature and pressure conditions. An inverse microscope objective of NA=0.65 and a working distance of 0.57 mm is used to focus the beam through a sapphire window onto a substrate, fixed in the vacuum chamber. The focus is moved in space by means of a piezo-driven stage with nm-resolution. Two-dimensional silver structures with dimensions in the sub-micrometer range are successfully deposited from the gas phase on glass substrates. Future investigations aim for extending the method into the third dimension.