Optical Wavelength

A second factor limiting the machining accuracy is the laser operating wavelength and/or the beam focusing optics.

The best focal spot is proportional to the wavelength divided by the numerical aperture (NA) of the focusing objective. Note that this observation would indicate that shorter wavelengths are always better than longer wavelengths. While this is theoretically correct, it is important to realize that most often heat diffusion imposes limitations that are much more restrictive than those dictated by wavelength and NA considerations.