Fabrication of 3-D photonic bandgap structures on silicon using laser assisted-nanoimprinting

A new approach to fabricate 3-D photonic bandgap structures on silicon substrates using colloidal crystals and laser-assisted nanoimprinting is presented. Self assembly was used to deposit two layers of silica micro particles with a diameter of 0.97 µm. A KrF excimer laser beam with a wavelength of 248 nm was vertically irradiated on the quartz plate placed on the silicon substrate containing two layers of silica particles. The silica particles were imprinted into silicon substrate by the quartz plate during the laser pulse irradiation. Ultrasonic cleaning and hydrofluoric-acid (HF) solution were then used to remove the silica particles. 3-D hemispherical cavities were formed on the silicon substrate surface.