Achieving a photonic band edge near visible wavelengths by metallic coatings

A metallic coating method is used to modify the optical properties of a dielectric photonic lattice and to achieve a near visible photonic band edge. It is experimentally shown that the linear scaling rule of a metallic band edge versus lattice constant holds only for perfect conducting metals. When a metal deviates from a perfect conducting behavior near the plasma wavelength, the metallic photonic band edge is pinned and is nearly independent of lattice constant. For our tungsten photonic lattice, the pinning occurs at λ≈1.5–2μm. By using a thin copper coating (∼70nm) to a dielectric photonic lattice, a photonic band edge at λ∼750nm is observed. This achievement is made possible by the fact that copper is a good conductor at visible wavelengths and the linear scaling rule holds. Finally, this coating method allows for tailoring photonic properties through material engineering at the nanometer scale.