Imitating the effect of amplified spontaneous emission pedestal at relativistically intense laser interaction with nanostructured solid targets

We investigated the effect of focusing sub-nanosecond laser radiation with varied fluence onto the surface of different flat and nanostructured targets utilized in ultra-high intensity laser-plasma experiments. Thus, we modeled the action of the prepulse, referred to as an amplified spontaneous emission pedestal, typically present for a relativistic (with peak intensity over 10(18) W cm(-2)) laser pulse with naturally limited contrast. The suppressed melting threshold was detected for the sub-wavelength scale structured material. Local melting leading to distortion of initial structures was detected at a fluence of similar to 0.2 J cm(-2) and below, or 3-5 times lower compared to the flat substrate melting threshold. It is also demonstrated that the threshold lowering is dependent on the production method of the structures, which may be attributed to increased absorption and suppressed heat transfer into the bulk.