Molecule aggregation in groove in Fused silica

[Sciencestd]

Image (a) is a view from above of a fused silica sample, the groove depth about one micrometer and the width is about 5 micrometer, the image (b) is a side view of the facet, when I cast a solution with molecules the aggregation is more on the grooves area which is logic, but when I shine a light on the groove from the side (in image (b)) the aggregation of the molecules on the groove enhanced and almost takes the shape of the groove...
What do you think is the reason?
The light source is a laser.

 

[Navin A S]

The reason for the enhanced aggregation of molecules on the groove when a laser is shone on it from the side is likely due to the increased surface area exposed to the light. When light is incident on a groove, the total amount of light that is absorbed is greater than if the same amount of light were incident on a flat surface because of the increased surface area. The increase in light absorption leads to an increase in the temperature of the groove, which in turn causes the molecules to aggregate more strongly within the groove due to increased thermal energy.