Crystalline 20- to 40-nm-diam Ge nanoparticles were precipitated periodically in Ge-B-SiO2 thin glass films fabricated by the plasma-enhanced chemical vapor deposition method. Such a periodic structure was created by exposure to an interference pattern with a KrF excimer laser (248 nm wavelength) and successive annealing at 600degreesC. Nanoparticles were precipitated predominantly in the unirradiated region after photoinduced refractive index change was erased completely after annealing up to 500degreesC. (C) 2004 American Institute of Physics.