Optical properties of a model pressed composite (potassium bromide matrix with incorporated ALEX aluminium powder) are experimentally investigated. It is shown that the spectral dependences of total transmittance and diffuse reflectance can be described with allowance for the presence of both individual aluminium nanoparticles and their aggregates with a characteristic radius of 133 nm in a sample. It is found that irradiation of a composite sample by a 1070-nm cw laser initiates nonlinear absorption of radiation by aluminium particles, which is detected by a change in the sample optical density. A model is proposed to describe the effect, which is based on the sample heating and temperature dependence of the optical characteristics of aluminium particles. The calculation results are in qualitative agreement with the observed changes in optical density; hence, the thermal mechanism of nonlinear absorption of electromagnetic radiation by metal particles is applicable to this model system.

通过实验研究了模型压制复合材料（溴化钾基体与 ALEX 铝粉）的光学特性。结果表明，总透射率和漫反射率的光谱依赖性可以在允许样品中存在单个铝纳米颗粒及其特征半径为 133 nm 的聚集体的情况下进行描述。发现用 1070 nm 连续激光照射复合样品会引发铝颗粒对辐射的非线性吸收，这可以通过样品光密度的变化来检测。提出了一个模型来描述这种效果，该模型基于铝颗粒光学特性的样品加热和温度依赖性。计算结果与观察到的光密度变化定性一致；因此，金属粒子对电磁辐射的非线性吸收热机理适用于该模型系统。