Role of thermal and photo annealing on nonlinear optical response of Ge30Se55Bi15 thin films.

In this article, we employed nanosecond Z-scan technique to demonstrate the nonlinear optical response in Ge30Se55Bi15 thin films after thermal and photo annealing. The intensity dependent open aperture Z-scan traces reveal that for all the samples, i.e. as-prepared, thermal and photo annealed thin films exhibit reverse saturable absorption (RSA). The experimental results indicate that both thermal and photo annealing can be efficiently used to enhance the nonlinear absorption coefficient compared to as-prepared sample. We further demonstrate that beta value of thermally annealed and as-prepared samples increase significantly at higher intensities. On the contrary, beta for photo annealed sample does not exhibit appreciable changes against the intensity variation.