Fabrication and annealing analysis of three-dimensional photonic crystals

Three-dimensional face-centered-cubic (fcc) photonic crystals (PhCs) are fabricated on quartz substrate using vertical deposition technique, and followed by annealing in a temperature range of 200-700 °C. The monodispersed SiO2 microspheres with a diameter of 220 nm in colloidal solution are synthesized using tetraethylorthosilicate as a precursor material. The as grown opal structure exhibits a strong photonic band gap (PBG) around 450 nm in the transmission spectrum. We find that the position of PBG peak in the spectrum is relevant to incident angle of light. Moreover, it is very sensitive to annealing temperature. It quickly shifts to short wavelength direction with annealing temperature increasing. The effect results from the decrease in refraction index due to the moisture evaporation in silica microspheres.