Role of thermal and photoannealing on nonlinear optical response of Ge30Se55Bi15 thin films

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