Single-step photopatterning of diffraction gratings in highly photosensitive hybrid sol-gel films

Inorganic-organic hybrid materials prepared by a sol-gel process showed a large photoinduced negative refractive-index change (2×10^-2) and a volume change. Diffraction gratings were made directly by irradiation with a KrF excimer laser (248 nm) through a phase mask without any etching process. The dependence of diffraction efficiency on irradiation conditions was investigated. The maximum diffraction efficiency, measured by the Littrow configuration with a He-Ne laser (633 nm), was 3.4% in reflection mode.