Influence of the transition layer material on the etched pattern of multilayer films

High-quality frequency-selective surfaces (FSSs) exert a crucial role in the absorption and filtration of electromagnetic signals. FSS is made from structure-function-integrated materials with a patterned metal layer cover. Cr or Ni transition layers are usually arranged between the material substrate and the metal layer to enhance their bonding. However, the study on the removal behavior of Al/glass and Al/Ni/glass films by laser ablation with a pulse width of 100 ns of the 1064 nm laser found that the Ni transition layer increases the damage threshold of Al films because its thermophysical parameters changed the laser absorption rate of the Al surface and the spatial temperature distribution inside the Al film. The experimental results show that four characterized areas in the laser ablation surface are identified in the machined grooves when the laser energy density is 12 J/cm2, indicating that the multilayer films are mainly removed by vaporization, phase explosion, melting, and fragmentation. It is found that the removal mechanism of the Al/Ni/glass system is dominated by melting heat stress and fragmentation, so splashing is obvious and results in residual recondensation droplets of micrometer size. The above results provide ideas and methods for other high-quality laser processing of structure-function-integrated film systems.