Thermal · photothermal heating
Optically, its reflections change how much light the particle absorbs; thermally, heat flows into the substrate too, so a well-conducting substrate (sapphire, silicon) keeps the particle much cooler than glass.
The particle's temperature rise for a given intensity and the temperature around it, with the substrate's optics and heat conduction.
Yes: a small gap to a metal film strengthens absorption through the gap mode.
The temperature of a particle on glass, silicon or metal under light, in one click.