Spectral Reflectance of the Close-Packed Structure of Silica Microspheres

The spectral reflectance of microperiodic structures of silica microspheres was investigated. The electromagnetic dispersion relation in a close-packed structure of silica spheres is computed. The three-dimensional close-packed structures, self-assembled with silica microspheres (2 μm and 3 μm), were rapidly fabricated over a large area. Specular reflectance was measured by using Fourier transform-infrared spectroscopy (FT-IR). The experimental results were evaluated by a modification of Bragg’s law, taking into account Snell’s law of refraction, and calculations of multiple reflections and the scalar wave approximation method. In addition, to expand the reflection wavelength range, a double-layered sample was fabricated, and its spectral reflectance was determined.