Scientists call this new mechanism a "multiphoton" or "nonlinear" process. Multiphoton simply means that many photons combine together to produce the machining effect.

Traditional laser sources used in laser machining don't have enough photons packed into a short enough time to produce these "multiphoton" effects. They are essentially single photon processes. Consequently, they must rely upon other mechanisms to remove material - like, for example, absorption. But absorption is a process that depends upon the wavelength of light being well-matched to where the material absorbs. If it isn't, then the material will not be removed.

With this new process, the peak power is so high that not only does the light overcome the forces that hold the material together, it overcomes the forces
that hold the atoms themselves together. The result is that as many as 15 electrons are stripped off of the atom almost instantaneously.This new process is not wavelength dependent. All it depends upon is that there be enough photons of light packed together into an extremely small period of time. It is, consequently, a threshold process, in that the number of photons packed together in time and focused onto the material must be high enough to produce the effect. But beyond this, it does not have a wavelength dependence.

As an example, glass is transparent to light at 800 nm wavelength. But a femtosecond pulse of light can machine pits inside glass when the light is focused inside the material and has sufficient intensity to exceed the threshold for multiphoton effects to occur.