The thermal lens effect on laser heating of a metal nano-sphere particle immersed in oil

In this work, we revise the model describing laser heating of a spherical metallic nanoparticle (NP) immersed in transparent oil. We study the generated temperature non-uniformity of the ambient medium and its effect on the propagation of the laser beam. Thus, the model describes the influence of thermal non-uniformity on scattering and absorption of light by the heated particle. Recently, different aspects of the heating of NPs by a laser beam have been actively researched. Some experimental works demonstrated an enigmatic dependence of the effective scattering cross-section of the heated particle on the intensity of the laser beam, illuminating it. The authors of these works labeled the observed effects as “saturation,” and “reverse saturation.” In this paper, we show that the propagation of the incident laser beam in a non-uniform oil can by itself be the source of both “saturation” and “reverse saturation” els effects.