Study On Photonic Bandgap And Fabrication Of Large Diameter Silica Colloidal Crystals

For application of photonic crystals working in the infrared, properties of some ordinary structures were systematically studied by combining the transfer matrix method and the plane wave expansion method in this thesis, and the classic convective flow induced self-assembly method was improved for the preparation of 800nm～5μm SiO₂ spheres colloidal crystal. Infiltration of Ge into the SiO₂ template was carried out by PECVD technique.1d photonic crystal bandgap properties, together with the omnidirectional reflection bandgap, were deeply examined. Calculations were also performed for the following structures: face-centered-cubic, body-centered-cubic, simple-cubic, simple-hexagonal, diamond, and woodpile, critical dielectric constants and gapmaps were directly obtained. The results guide our experiments greatly.For preparation of 800nm SiO₂ colloidal crystals, different hydrophilic solvents were adopted as dispersants, after comparison the proper ones were identified and best deposition temperature were found respectively.For the sake of preparing larger diameter silica microspheres colloidal crystal, three approaches were introduced. The first one involving dispersing the surface-modified silica spheres into a high density hydrophobic solvent, the second one including directly dispersing the microspheres into binary solvents. The best binary systems, components ratio and proper temperature were finally determined. Surface assembly of silica microspheres were also realized for the first time by applying the binary system and large area single 1.8μm and 1.86μm SiO₂ colloidal crystal was successfully fabricated.Ge was infiltrated into the SiO₂ template by PECVD using GeH₄ as a precursor, and Ge inverse opal was finally obtained by removing the SiO₂ matrix. The work may promote the application of photonic crystal in new infrared optoelectronic devices.