High contrast plasma mirror: spatial filtering and second harmonic generation at 1019 W cm-2

Recently, the use of plasma optics to improve temporal pulse contrast has had a remarkable impact on the field of high-power laser-solid density interaction physics. Opening an avenue to previously unachievable plasma density gradients in the high intensity focus, this advance has enabled researchers to investigate new regimes of harmonic generation and ion acceleration. Until now, however, plasma optics for fundamental laser reflection have been used in the sub-relativistic intensity regime (10 15 -10 16 Wcm 2 ) showing high reflectivity ( 70%) and good focusability. Therefore, the question remains as to whether plasma optics can be used for such applications in the relativistic intensity regime (>10 18 Wcm 2 ). Previous studies of plasma mirrors (PMs) indicate that, for 40fs laser pulses, the reflectivity fluctuates by an order of magnitude and that focusability of the beam is lost as the intensity is increased above 5◊10 16 Wcm 2 . However, these experiments were performed using laser pulses with a contrast ratio of 10 7 to generate the reflecting surface. Here, we present results for PM operation using high contrast laser pulses resulting 5 Author to whom any correspondence should be addressed.