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42%P 2 O 5 -40%ZnO-2%CaO-(16-x) %Na 2 O-xCu 2 O glass system (x=o, 2, 4, 6, 8, 10%mol) were prepared by conventional melt-quenching technique. It was investigated by means of electron paramagnetic resonance (EPR) to study the structural changes induced by different amount of copper ions. The spin Hamiltonian parameters like g∥ , g⊥ and A∥ show that Cu +2 ionare in tetrahedral coordination with d xy as the ground state. Modification of EPR band width by increasing copper content suggests that band consists of two overlapping bands; one of them is related to asymmetric band due to isolated copper ions and the other is symmetric due to cluster ions Cu +2 -Cu +2 . Calculation of the optical basicity indicates to that polarizability decrease by increasing copper content due to increase electron cloud density at the Cu 2+ site.

T HE INFLUENCE of compositional variations on the physical properties such as, density, molar volume, ,molar refraction, optical energy gap, refractive index , optical basicity, oxide ion polarizability, metallization, and third order nonlinear susceptibility, nonlinear refractive index, with the variation in Nb 2 O 5 content has been studied theoretically for glasses of compositions xNb 2 O 5 (20-x)BaO80TeO 2 (x=0, 5, 10,15) and the physical parameters related to these compositions were analyzed with theoretical predictions.The density calculated decreases with the increase of Nb 2 O 5 content from 5.680 g cm -3 to 5.493 g cm -3 , this means that the glass matrix becomes less dense. It was found that , the optical energy gap decreases, but the refractive index increases by increasing Nb 2 O 5 content.The electronic polarizability of oxide ion decreases with decreasing the optical basicity. The value of optical basicity shows that the glass materials are less basic. It is suggested that by increasing Nb 2 O 5 content ,the glasses become less polarized. Also, It was found that the values of third order nonlinear susceptibility increases by increasing Nb 2 O 5 content and are found to be larger than those of the silica based glasses. The glasses are found to possess a high refractive index (2.170-2.213), a comparatively narrow band gap (3.992eV-3.785eV), high electronic ion polarizability (2.445 Å 3 -2.546 Å 3 ) and high optical basicity (0.987-1.014). It was found that the values of the third order nonlinear optical susceptibility are in the range (0.7604-0.9271)x10 -12 esu. Finally, all the above values are a good basis for predicting new non linear optical materials.

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