Achieving Complete Bandgaps by Self-Similar Spherical Structure Using Low Refractive Index Materials

A three-dimensional complete bandgap (CBG) in the visible range is achieved by a self-similar spherical photonic crystal (PC) fabricated using the materials with low refractive index. A novel holographic technique is developed to fabricate such a structure. A CBG with a width of 120 nm is obtained experimentally. Even though the light not passing through the center of the sphere incidents on the PC with an incident angle of 49, a 30-nm-wide CBG can still be kept. Theoretical analysis is also given in which experimental results can be well explained.