We show, from theoretical calculations including the absorption losses
in metal layers, that the transmittance of a one-dimensional metallic
photonic crystal can be increased up to 67%. The structure consists of
five layers of Ag and four layers of GaN. The layer thickness of Ag is
30 nm, and that of GaN 64 nm. We further add one GaN layer of 32 nm at
the top and the bottom, respectively. The total thickness of Ag layers
in this photonic crystal is 150 nm, which is several times longer than
the skin depth of Ag. However, we could achieve the peak value of 67%
transmittance at 500 nm wavelength owing to the two half thick GaN
layers added at the top and bottom of the film. Without these
additional two layers, strong oscillations appear in the transmittance
spectrum with the peak value of only 30%. When only one half-thick GaN
layer is added to the structure, the oscillation becomes smoothed out
so that the overall transmittance increases, but the peak value is
still 30%. The two additional layers make the spectrum smoother and
further increase the transmittance.