Various evaluations of a diffractive transmitted field of light through a one-dimensional metallic grating with subwavelength slits

We compare the Fresnel-Kirchhoff diffraction formula, the superposition of cylindrical waves, and the twodimensional (2D) Green’s function diffraction formula with a rigorous vector algorithm in calculating the near and intermediately transmitted field of light through a one-dimensional metallic grating with subwavelength slits. It is found that the results calculated by the 2D Green’s function diffraction formula coincide well with the precise result. The other evaluations deviate from the exact result by varying proportions. Our findings may provide a useful and precise way to analyze the transmitted field features of a metallic grating and subsequent possibility of achieving optimal designs for metallic optical elements with subwavelength scale.