Thermo-Optical Nonlinearity of Metallic Nanoparticle(s)

Over the last few decades, extensive previous studies of the nonlinear response of metal nanoparticles report a wide variation of nonlinear coefficients, thus, revealing a highly confused picture of the underlying physics. Here, we provide a systematic study of the nonlinear response of metal spheres under continuous-wave illumination within a purely thermal model. The improved modeling allows us to demonstrate a much better match to experimental measurements of the scattering from single metal nanoparticles compared to previous attempts. We then use these results to study the thermo-optical nonlinearity of many-nanoparticle composites. We show that the thermo-optical nonlinearity of the composite is strongly sensitive to the host thermal conductivity only. Our results can be used to interpret correctly the differences in chemical reaction enhancements originating from the thermo-optical nonlinearity at different illumination intensities.