Femtosecond Laser Induced Metal And Dielectric Nanostructures And Their Color Display Applications

Nanophotonics is an important research direction in the field of optics,mainly studying the interaction between light and matter at the nanoscale.In nanophotonics,metal and dielectric nanostructures are widely used in light field control,and femtosecond lasers have the advantages of short pulses and high instantaneous energy.Therefore,femtosecond lasers can be employed to induce certain nanostructures to achieve high-resolution and ultra-small color prints.In this thesis,femtosecond lasers are employed to process the pre-fabricated cross-shaped aluminum nanorod structures and titanium dioxide dielectric thin films,respectively,to achieve multi-functional color display and obtain color display and directional scattering function of nanoparticles.The main innovation points and research contents of this thesis are as follows:1.Linearly polarized femtosecond laser was used to reshape the cross-shaped aluminum nanorod structures.By controlling the polarization angle in 0°and 90°,the constituted nanorods of the cross structures can be reshape individually.Tuning the laser power can control the final shape of the nanorods and the corresponding plasmon resonance wavelengths,achieving full color prints in the visible range.Furthermore,polarization multiplexed color images are printed and demonstrated.2.The polarization angle of the lasers was changed from 0°to 90°with every10°step for printing,so that the two aluminum nanorods can shrink simultaneously.Depending on the laser polarization angle and power,anisotropic color display,i.e.,color changes when the incident white light polarization angle changes,can be obtained.We give the reflectance formula and compare the experimental spectrum with the simulated spectrum to explain the reason for the anisotropic color display.3.Femtosecond lasers were used to splashe dielectric titanium dioxide nanoparticles from titanium dioxide thin films.We have observed that individual Ti O₂nanoparticles can show different colors with different size and there are differences in forward and backward scattering,with different colors.We have found through theoretical calculations that Ti O₂ nanoparticles show significant difference in forward and backward scattering,presenting directional scattering properties in the visible range.In the experiment,we measured the forward and backward scattering spectra of single particles and verified their directional scattering properties.