Plasmonic Color Printing with Semicontinuous Silver Films and Modeling of Inhomogeneous Broadening

Among many kinds of plasmonic structures, semicontinuous metal films (SMF), which are randomly distributed metal nanoparticles at the near-percolation regime, can generate sub-wavelength, fade-free, and environment-friendly plasmonic colors. SMFs comprise of random, fractal-type island films with nanoparticles which resonate at different wavelengths. Such structures can confine light at the nanoscale under illumination and result in an enhancement of the local electromagnetic field. Laser illumination reshapes the metal nanoparticles through thermally induced changes allowing for vibrant colors due to spectral modification. In this work, we have an asymmetric Fabry-Pérot plasmonic structure comprising of semicontinuous metal films deposited on a metallic (Ag) mirror with a thick dielectric (SiO₂) to utilize the multiple-beam interference and observe colors in the reflection mode. The absorption of SMF exhibits inhomogeneous broadening and hence was fitted with Lorentz-convoluted models where the statistics of the nanoparticles is accounted for with a probability distribution. In order to implement such dispersion in frequency/time domain solvers we developed a time-domain compatible analytical approximation based on our generalized dispersive material (GDM) model framework.