Fabrication, characterization and simulation of large-scale 3-D photonic crystals using laser-assisted fabrication techniques

3-D photonic bandgap (PBG) structures were fabricated by laser-assisted fabrication techniques, including laser-assisted nanoimprinting and laserassisted chemical vapor deposition (LCVD), based on the self-assembled silica colloidal crystals. The multilayer silica colloidal crystals self-assembled on silicon substrates were formed with isothermal heating evaporation-induced self-assembly. To infiltrate the silica colloidal crystals, the laser-assisted imprinting technique was used using a short pulse (pulse duration 23 ns) of a KrF excimer laser. The nanosecond laser pulse instantaneously melted the silicon substrates, which infiltrated and solidified over the assembled silica particles on the substrates. By removing silica particles embedded in the silicon using hydrofluoric acid, inverse opal photonic crystals were produced. To utilize the LCVD technique, a continuous wave (CW) CO₂ laser (10.6 μ m wavelength) was used as the energy source. A silica-core-silicon-shell PBG structure was obtained. This technique is capable of fabricating structures with various PBGs by obtaining different silicon shell thickness with different LCVD parameters. A series of PBG structures with designed PBGs were obtained with different experimental conditions. Spectroscopic ellipsometry was used to identify specific PBGs. The plain wave expansion (PWE) simulation was used to simulate the photonic dispersion diagrams of the structures, which agreed with the experimental results.