Based on the characteristics of evanescent wave moiré fringes generated from subwavelength gratings, we numerically investigated the contrast of moiré fringes for two gratings with and without a silver slab. The effect of the gratings’ geometrical parameters on the contrast of moiré fringes is analyzed in detail by using the finite-difference time domain method. Numerical results show that great enhancement of the contrast of evanescent wave moiré fringes could be achieved by surface plasmon excitations on a silver slab. These evanescent wave moiré fringes with high contrast will have potential applications in the nanofabrication field.
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