In certain field of physics, particularly in attosecond research, scientist are looking for interact a ultra-high laser field (up to 1021 W/cm2) with a solid. One of the experimental limt is the contrast ratio of a such laser pulse. “En effet”, depending of the material, a solid start to be ionized (and become a plasma) around 1010 W/cm2. Without special technic, femtosecond laser have a contrast around 10-6 or 7. This lead to produce a pre-plasma which will expand before the peak of the pulse interact with the target, and then interact with a lower density target.

One of the technic to increase the contrast is to use a plasma mirror or two as shown on the picture.

A laser beam beam is focused on a piece of glass. It will be transmit until it reach enough intensity and produce a plasma. At that moment, the reflective index change, the beam is then reflected on the free electron.

So, the “pied d’estale” of the beam is suppressed and the contrast ratio increase.

The first group showing the potential of this method are ...

Last update : 2012 March

©RSMarjoribanks 2008,09,12