Ultraviolet (UV) pulses at 450 fs are a powerful tool for femtosecond laser waveguide writing in fused silica. Whereas typically sub-200 fs pulses at a high exposure dose were required, UV light efficiently creates waveguides with propagation losses below 0.1 dB/cm at high writing speed. The experimental setup is shown in Fig. 1(a). Linearly polarized light at a wavelength of 343 nm is focused into the bulk with an NA of 0.38 and the sample is mounted on mechanical x-y- stages. The high intensity within the focal volume locally increases the refractive index through laser-induced densification.