Enhanced light diffraction from self-assembled double-layer colloidal crystals

We demonstrate that double-layer colloidal photonic crystals function as wavelength-and polarization-insensitive blazed transmission gratings with efficiencies as high as 63% in the high-energy spectral region. This phenomenon, which is known as specular-resonance-enhanced diffraction, has been reported for a small-scale cluster of microspheres with a limited size parameter. By performing accurate characterization employing large-area colloidal crystal films self-assembled by an inclined dip-coating method with a controlled number of layers, this peculiar and efficient diffraction was demonstrated to be a universal property of double-layer colloidal crystal films. (C) 2011 American Institute of Physics. [doi:10.1063/1.3636104]