Absorption enhancement by a period array of nano-grooves in gold substrate

Comprehensive investigations of absorption enhancement by a period array of nano-grooves in gold substrate are provided. A simple Fabry-Perot model is presented to explore impact factors on absorption enhancement. The impacts of structural parameters on absorption enhancement for an array of nano-grooves are explored and discussed. Our calculations show that complete absorption (about 1) can be obtained with the groove depth fulfilling the Fabry-Perot resonance condition. The effect of groove width on absorption for a trapezoidal groove array is slightly different from that for a rectangular groove array, because of the impact of single-pass loss in the grooves. Surface plasmon resonance that can carry most of the energy away from grooves and propagate along the metal surface could lead to extremely low absorption for a period array of nano-grooves. Our discussions identify two key roles in absorption enhancement for a nano-groove array: the fundamental groove mode resonance and the generation of surface plasma polaritons. In addition, the analysis of absorption enhancement for an array of trapezoidal grooves can also provide a comprehensive contribution of Fabry-Perot resonance and electromagnetic interaction along the bevel edges of the trapezoidal grooves.