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 1018 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 ~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.

中文翻译：

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模拟放大自发发射基座在相对论性强激光与纳米结构固体目标的相互作用中的作用

我们研究了将具有不同能量密度的亚纳秒激光辐射聚焦到超高强度激光等离子体实验中使用的不同平面和纳米结构目标的表面上的影响。因此，我们模拟了前脉冲的作用，称为放大自发发射基座，通常存在于具有自然有限对比度的相对论（峰值强度超过 1018 W cm-2）激光脉冲中。检测到亚波长结构材料的抑制熔化阈值。在~0.2 J cm-2 及以下的注量下检测到导致初始结构变形的局部熔化，或比平坦基板熔化阈值低 3-5 倍。还证明了阈值降低取决于结构的生产方法，