Abstract

In a noble metal nanoparticle system, such as gold or copper, an absorption peak due to a surface plasmon is mostly observed in the visible region. Particularly, in a SiO₂ matrix, the absorption peak appears near the edge of the band-to-band transition. Figure 1 shows the absorption spectrum (solid curve) with results of the calculation by the Mie scattering theory (dotted curve) at room temperature. Contributions of the Drude part and the interband part are also depicted as a broken curve and a chain curve, respectively. In our previous study, the non-linear response was found to originate mainly from the hot electron which was heated by the incidence of a pump pulse in the sub-picosecond region.¹⁾ In consideration of the thermal diffusion process from metal nanoparticle to the host matrix, the total energy flow in the metal nanoparticle system was explained quantitatively. We have found that the lattice temperature is also raised even in the first stage of the non-equilibrium state and the non-linear response is governed by the thermal equilibrium process described by the electron-phonon (e-p) coupling model.

© 1998 IEEE