EXPERIMENTAL STUDY ON NONLINEAR OPTICAL PROPERTIES OF METAL CLUSTERS SERIES

Abstract

In this thesis, we have experimentally examined the nonlinear optical properties of the metal clusters series. A simple but effective technology - Z-scan technology is used as the main tool to obtain both the quantity and sign of the nonlinearities of our samples. Compared with other materials, large nonlinear index and low linear absorption in the visible wavelength range are demonstrated in our metal cluster samples, which made our samples promising candidates in the application of optical limiting. A five energy level model of excited states absorption we employed can well explain the electronic nature of the nonlinear absorption in our metal cluster series. To explore the nature of nonlinear refraction index of our samples, we attempt to use nonlinear K-K relation. The changing of the sign of nonlinear refraction index is well explained by the theory, the quantity predicted by the theory still have large discrepancy with the data processed in the same procedure using our experimental data ofn2. Focused on the practical problems raised in the real limiting devices, we also demonstrate a method to realize the alternation of the nonlinear refractive index in a mixture of two metal cluster compounds. Such a mixture makes it easy to optimize the arrangement of the elements in hybrid limiting devices. The phenomenon is extremely useful in the realization of nonlinear optical element which can be used as a protector in the self-protected optical limiting device.