The present work reports the effect of heat treatment under vacuum on the optical properties of Ge₂₀Se₆₅S₁₅ thin films prepared by the thermal evaporation technique. The structural units and the surface morphology of the films were characterized using Raman spectroscopy and scanning electron microscopy (SEM), respectively. The optical parameters of as-deposited and annealed films were calculated using the Swanepoel's method from the optical transmission spectra \( T\left( \lambda \right) \) in the wavelength range of 300–2500 nm. The variations of Urbach energy E_U and optical energy gap \( E_{\text{g}}^{\text{Opt}} \) with the annealing temperature are discussed in terms of the density states model in amorphous solids. The refractive index dispersion is analyzed and discussed in terms of Sellmeier and Wemple–DiDomenico models. The nonlinear susceptibility \( \chi^{\left( 3 \right)} \) and nonlinear refractive index n⁽²⁾ were evaluated based on the generalized Miller’s rule as a function of annealing temperature. Lastly, the two-photon absorption coefficient (β_c) was obtained theoretically via \( E_{\text{g}}^{\text{Opt3}} \) scaling law.

本工作报道了真空热处理对通过热蒸发技术制备的Ge ₂₀ Se ₆₅ S ₁₅薄膜的光学性能的影响。分别使用拉曼光谱法和扫描电子显微镜（SEM）表征膜的结构单元和表面形态。沉积和退火后的薄膜的光学参数是使用Swanepoel方法从300–2500 nm波长范围内的光学透射光谱\（T \ left（\ lambda \ right）\）计算得出的。Urbach能量E _U和光能隙\（E _ {\ text {g}} ^ {\ text {Opt}} \）的变化根据非晶态固体的密度状态模型讨论了退火温度的变化。根据Sellmeier和Wemple–DiDomenico模型对折射率色散进行了分析和讨论。非线性磁化率\（\ chi ^ {\ left（3 \ right）} \）和非线性折射率n ^（2）基于广义米勒法则作为退火温度的函数进行评估。最后，双光子吸收系数（β _{c ^}经由理论上获得）\（E _ {\文本{G}} ^ {\ {文本} OPT3} \）的比例定律。