Hello:

Dr. John Bellum who is a member of RG is an expert on laser damage. You may want to message him.

Hi Stefan --

There are many ways to improve the pulse contrast of an ultrahigh-power laser system, and different methods may be more or less suitable for your laser scheme.

Generally speaking though, whether implemented before (like in a double CPA laser system) or after the final amplifiers, a lot of pulse cleaning methods use nonlinear optical processes since the throughput is much higher for the main pulse than for the undesired optical garbage (e.g. pre-pulses from regenerative amplifiers, amplified spontaneous emission or super-fluorescence, scatter that shortcuts through the system, etc.) that would otherwise pre-expose your target to damage, like you said. Certainly plasma mirrors fall into this category (using the nonlinear optical process of strong-field ionization to modify the reflectivity of the substrate); other techniques that you can readily find in the scientific literature include cross-polarized wave generation (XPW), (chirped-pulse) optical parametric amplification ((OP)CPA), nonlinear polarization rotation, saturable absorption, second harmonic generation (SHG), or even combinations of several of these to increase the contrast between the main pulse and the unwanted surrounding optical signal.

Try searching for laser pulse contrast, and you'll quickly chance upon a bevy of techniques that will get you started down your line of inquiry.

Good luck,

~Eric

Hello,

Instead of using a plasma mirror one could use a saturable absorber in transmission (e.g. https://www.batop.de/products/saturable-absorber/saturable-absorber/saturable-absorber.html) with well-defined intensity-dependent absorption/transmission characteristics....