Nonlinear optical response of polycrystalline GeSe films.

GeSe exhibits in-plane optical anisotropy similar to black phosphorus and other two-dimensional materials, so it is believed to have remarkable nonlinear optical (NLO) properties. In this work, amorphous GeSe films were prepared by vacuum thermal evaporation. After annealing at 450 °C, GeSe films exhibited a polycrystalline phase. The NLO properties of these GeSe films were investigated by the Z-scan technique. The results indicated that GeSe films exhibited typical reverse saturable absorption (RSA) and self-focusing phenomenon. It was also found that the nonlinear optical parameters and laser-induced damage threshold of annealed recrystallized GeSe films were significantly improved. The nonlinear absorption and refractive coefficients were β = (2.90 ± 0.06)×10−7 m/W and n 2 = (1.06 ± 0.07)×10−13 m2/W at the incident laser intensity of 0.4 GW/cm2, respectively. The polycrystalline GeSe film showed remarkable RSA-induced optical limiting properties, which exhibited an optical limiting starting threshold of 0.018 GW/cm2 and an optical limiting threshold of 0.98 GW/cm2. These results strongly indicate that GeSe films have potential applications in solid-state optical limiting devices and laser protection. [ABSTRACT FROM AUTHOR]