Using femtosecond laser pulses it is possible to produce true three-dimensional photonic structures in different glasses and crystalline media. This direct writing process offers great flexibility, however, it has the drawback of a comparatively slow processing speed. In this presentation we will demonstrate a possibility to overcome this limitation. Based on a fiber based CPA system producing 300 fs pulses with pulse energies of up to 1 μJ and repetition rates in the MHz range we fabricated low loss waveguides (propagation losses 0.5 dB/cm) inside silicate glasses at high writing speeds up to 100 mm/s, limited only by the positioning system. The achieved refractive index changes are > 0.01. The influence of the processing parameters (writing speed, pulse energy) on the induced changes and the waveguiding properties will be discussed in detail.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.