Excimer Light and Material Interaction

Materials react to excimer laser UV light in several ways:

Photochemical changes

When materials are processed by excimer lasers a photochemical color change occurs. The change occurs in plastics and ceramics at raw beam power densities.
Excimer UV light alters the surface molecular structure, resulting in change of light absorbing properties.

Photo-ablation

At higher power densities, excimer UV light energy breaks molecular bonds in material.
Small interaction volume due to shallow absorption depth limits heat conduction.
Ablation by-products and excess heat are carried away by expansion of plasma plume.

Thermal effects

As power density increases, absorption depth increases, resulting in larger interaction volume. Greater volume results in increased heat conduction to surrounding material.
As pulse repetition rate increases, residual heat cannot escape, resulting in thermal effects.
Laser light absorbed by materials below threshold for ablation can impart significant heat to material.
Certain materials, such as metals, are removed by thermal input at high power densities. However, small interaction volume helps control thermal damage.