Application Of Containerless Solidification In3D Photonic Crystals

As periodic dielectric structures with photonic band-gaps, photonic crystals attractlots of attention of researchers. Meanwhile, researchers have done plenty of work oncontainerless solidification processing which is a novel process in preparing amorphousspherical glasses and single crystals. In this work, containerless solidificationprocessing was introduced for the first time to fabricate photonic crystals.Micrometer-sized amorphous BaTi2O5and La4Ti9O24spheres with perfect sphericalshape and superior optical properties such as high refractive index (n=2.15) weresuccessfully produced through containerless solidification processing.3D opal photoniccrystal was assembled with these spheres by spaced-confined method using a box ofprecisely controlled size. Plane-wave method was implemented to calculate bandstructures and analyze influence of refractive index on the band-gaps. The obtainedresults show that this3D opal structure has incomplete band-gap, and band-gap narrowsand moves toward lower frequency with the increase of refractive index along the [111]direction.Mie resonance theory and terahertz spectroscopy are used in the measurement ofdielectric constant and refractive index of the amorphous balls which pile into photoniccrystals. Meanwhile, Network analyzer is applied in the measurement of the photoniccrystals band gap position. Results shows that dielectric constant of BaTi2O5amorphousball is about22and the gap position of the photonic crystals range from40GHz to44GHz which is in basic agreement of the theoretical value (from37.2GHz to38GHz).Then La4Ti9O24amorphous balls are fabricated and measured in the same way.Dielectric constant of these balls is about40and plane wave expansion method is usedto simulate band gap of the photonic crystals composed of La4Ti9O24amorphous balls,and result shows the theoretical band gap position range from39.7GHz to42.15GHz.Results demonstrate that containerless solidification processing combined withprecise slicing technology provides an approach to fabricate superior spherical materialswhich can be used to form photonic crystals. By controlling compositions and sizes ofthe materials, location and width of photonic crystals band gap can be regulated.