A broad-band perfect absorber composing a two-dimensional periodic metal-dielectric-metal sandwiches array on dielectric/metal substrate is designed and numerically investigated. It is shown that the nearly-perfect absorption with a bandwidth of about 50 nm in visible region can be achieved by overlapping of two plasmon resonances: one originating from the coupling of electric dipoles between adjacent unit cells and another arising from magnetic dipole plasmon resonances. A capacitor-inductor circuit description is introduced to explain the dependence of resonance frequencies and band-width on geometrical parameters.

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The third-order nonlinear optical properties of two novel fullerene derivatives under picosecond laser excitation have been investigated by the Z-scan technique. The experimental results reveal that all the derivatives have nonlinear absorption coefficient under excitation of 532 nm pulses and a high third-order nonlinear refraction index under excitation of 1064 nm pulses. The molecular second hyperpolarizabilities have been obtained from our experimental results.

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