The effect of graded nanometal particles and their shape on the enhancement of nonlinear optical properties of oxide glasses

In the optical and infrared spectral ranges, nanometal particles such as Au, Ag and Cu have large real and small imaginary dielectric constants, so they possess strong plasmon resonance frequencies and large local fields. Metal nanoparticles change the nonlinear optical properties of glasses. Third-order nonlinear susceptibilities chi((3)) of composite glasses with ellipsoidal nanometal inclusions have been calculated using the T-matrix method. We have investigated the effect of the shape of nanometals on the nonlinear optical properties of oxide glasses. It was found that the results of our model and the experiment compare well and spherical metal nanoparticles change the nonlinear optical susceptibilities of glasses more than cylindrical ( two dimensional) nanoparticles. It is shown that if nanometals are included in glasses as graded profiles, their figure of merit (FOM) increases significantly and hence makes them promising materials for photonic applications such as all-optical switching. The FOM of SiO2 has been found to be enhanced by a factor of 6-7 by the inclusion of graded Au and Cu nanoparticles.