Fabrication of 2-D and 3-D photonic bandgap (PBG) structures on silicon substrates using laser-assisted nanoimprinting of silica particles has been investigated. Monolayers of silica particles, with different diameters ranging from 160 nm to 5 νm, were deposited on silicon substrates by self-assembly. A quartz plate, which is transparent to the laser wavelength of 248 nm, was tightly placed on the substrate surface. A KrF excimer laser beam with the wavelength of 248 nm was vertically irradiated on the quartz/nanoparticle/silicon structure. The silica particles were imprinted into silicon substrates by the quartz to form a 2-D PBG structure due to the transient Si surface melting during the laser pulse. 3-D PBG structures can be fabricated by directly imprinting multilayer self-assembled silica particles into Si substrates. They can also be fabricated by repeating a process cycle of silica nanoparticles self-assembly, amorphous Si layer deposition, and simultaneous laser melting, imprinting and recrystallization.