Reflection of high-intensity nanosecond Nd:YAG laser pulses by metals

Abstract

Total reflectivity of silver and molybdenum samples irradiated by high-intensity nanosecond Nd:YAG laser pulses in air of atmospheric pressure is experimentally studied as a function of laser fluence in the range of 0.1–100 J/cm2. The study shows that at laser fluences below the plasma formation threshold the total reflectivity of both silver and molybdenum remains virtually equal to the table room-temperature reflectivity values. The total reflectivity of these metals begins to decrease at a laser fluence of the plasma formation threshold. As the laser fluence increases above the plasma formation threshold, the reflectivity sharply drops to a low value and then remains unchanged with further increasing laser fluence. Calculation of the surface temperature at the plasma formation threshold fluence shows that the surface temperature value is substantially below the melting point that indicates an important role of the surface nanostructural defects in the plasma formation on a real sample due to their enhanced heating caused by both plasmonic absorption and plasmonic nanofocusing.