When using a laser to process material, energy (light) is inserted into the material which needs to be absorbed in order to convert the material from a solid into a liquid and vaporized state. A laser has a specific wavelength and therefore the efficiency of the laser process to remove material depends on how well the laser wavelength (light) is absorbed by the material which needs to be processed.
Wavelength (λ) used for laser material processing has several impacts.
As a general rule the majority of materials absorb better in the shorter wavelength regime Ultra Violet (UV) vs. the (near) Infra Red (IR).
When going toward far infra red regime (10,000nm) the absorption again starts to increase. But in the far IR regime the thermal effects become too large and therefore the HAZ as well.
The ability to achieve a certain spot size is related to the wavelength of the light. In the equation above it is show that a shorter wavelength allows to focus to a smaller spot size.