Femtosecond laser Wavelength-Dependent formation of plasmonic gold nanostructures

Complex gold nanostructures fabricated on the surface of metal have a high potential for being used as plasmonic nanostructures. The precise shape and dimensions management of the structures enables accurate control of plasmonic properties. In this work, the formation of gold nanobumps, nanocones, and nanojets by laser direct writing technique was investigated using different laser wavelengths by changing harmonics. The used wave-length of laser irradiation impacts the size and shape of the formed structures. Additionally, the achievable minimal grating period, the layer modification fluence, and the formation fluence range change with the used laser harmonic. Experiments indicate that the reduction of the wavelength provides a more precise fabrication process and management of properties. The gratings of the wavelength-dependent nanostructures excite surface lattice resonances with high quality and have significant potential for practical uses.