High-repetition-rate and multi-pulse ultrashort laser damage of gold-coated photoresist grating

Abstract The gold-coated photoresist grating (GCPG) compressor is a core module of the high-repetition-rate superintense ultrafast lasers. Understanding how pulse trains with different repetition rates lead to laser-induced damage of GCPG is critical for future high-power laser applications. In this paper, we present the results of a multi-pulse laser-induced damage threshold (LIDT) investigation of GCPGs at different high repetition rates for the first time. The upper and lower endurance limits of S-on-1 beam-normal LIDT at 50–1000 Hz (800 nm, 35 fs) are ∼0.40 J/cm2 and 0.01 J/cm2, respectively, and the multi-pulse LIDT at 100 kHz is ∼0.02 J/cm2 corresponding to the peak intensity ∼64 GW/cm2 (1030 nm, 320 fs). The typical damage morphologies at 50–1000 Hz that the gold coating strips from the photoresist grating mask differ from those initiated from the expansion of the mask at 100 kHz. Focused ion beam scanning electron microscopy measurements show that the corners and small adhesion strength of interfaces are structural weaknesses. Moreover, theoretical modeling indicates that the differences mainly arise from pyrolysis and low heat-conduction of the mask. Overall, these results are highly practical and lay the foundation for the safe construction of high-repetition-rate ultra-high-power lasers based on the GCPG compressor.