Modulation instability of incandescent light in a photopolymer doped with Ag nanoparticles

Abstract

We report the modulation instability and spontaneous filamentation of a broad incandescent beam propagating in a photopolymerizable medium containing a uniform distribution of Ag nanoparticles. Modulation instability (MI) originates from refractive index changes due to polymerization along the propagation path of the optical field. Because photoinduced changes due to polymerization are irreversible, the self-trapped filaments permanently inscribe the corresponding array of cylindrical waveguides dispersed with Ag nanoparticles. Careful examination of the dynamics of MI and calculations of parameters such as the self-trapping efficiency and average separation distance of filaments reveal a strong dependence on the concentration of Ag nanoparticles as well as the pathlength of the sample. Microscopy of the photoinduced waveguide microstructures identified a range of interactions between self-trapped filaments such as fusion, branching and repulsion.