Tunable photonic crystals by mixed liquids

Tunable photonic crystals were prepared by infiltrating mixed liquids into the voids of silica opals. The stop bands of the tunable photonic crystals were continuously tuned by changing the relative refraction index contrast nmix/nspheres of the spheres and the mixed liquids by varying the volume fraction of the component of the mixed liquids. The peak wavelengths of the stop band have a red shift as the refractive index of the mixed liquids increases. The transmittance at the stop band decreases with the increase of the refractive index contrast nmix/nspheres. The larger the diameter of silica opals is, the wider the tunable range of the stop band is. The position and transmittance of the peak wavelength obtained by the photonic band calculations agreed very well with the experimental data.