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Non-linear refractive index of a-Ge-Se-In-Bi glassy thin films

Ishu Sharma and P. B. Barman

To explore the potentialities of chalcogenide glasses for ultrafast optical switching, in this paper we report the measurements of non-linear refractive index of amorphous Ge20Se70-xIn10Bix (x = 0, 2, 4, 6, 8, 10) chalcogenide glasses. The formulation proposed by Fournier and Snitzer has been used to predict the non-linear behavior of Ge-Se-In-Bi system. The linear refractive index and Wemple-DiDomenico parameters were used for the determination of nonlinear refractive index in the wavelength region 400 to 1500 nm. This is observed that non-linear refractive index increases linearly with increasing linear refractive index. Non-linear refractive indices, three orders higher than silica glass, have been obtained in the ternary system. Third-order optical nonlinear susceptibilities (χ (3)) has also been evaluated from changes of index of refraction using Wang approximations. The addition of Bi drastically increases the non linear refractive index. We examined the dependence of susceptibility on the absorption edge, thereby showing that the susceptibility rapidly increases with the red shift in absorption edge. Comparison of our results shows a good agreement with values available in the literature at 1.55 eV.