Structural phase transition as the mechanism of an optical nonlinearity in a nanoparticle film

Optical control of phase coexistence, previously used as a mechanism for achieving a nonlinearity at planar gallium/glass interfaces, can be exploited as a nonlinear response mechanism in a metallic nanoparticle film. Experimental measurements of the reflective and transmissive nonlinear response of a gallium nanoparticle film, manufactured on the tip of an optical fibre using the light-assisted self-assembly technique, are shown to be consistent with an effective medium theory for the optical properties of a layer of closely packed nanoshells comprising a core and surface layer in two different structural phases of the metal.