Femtosecond laser microfabrication attracts much attention due to its ability to write three-dimensional photonic devices into various transparent materials. By optimizing laser processing parameters and annealing at high temperature, low-loss straight optical waveguides are written in a pure silica glass. The minimum propagation-loss is 0.05 dB/cm at the wavelength of 1550 nm. The utility of the femtosecond laser processing is demonstrated by writing a low-loss three-dimensional 1×8 optical splitter.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.