High-speed femtosecond UV laser writing of low-loss waveguides in fused silica

We demonstrate ultra-low-loss femtosecond laser-written waveguides in fused silica using 450 fs ultraviolet pulses from a frequency-tripled ytterbium laser. This favorable regime only appears at a low pulse density, enabling a two orders of magnitude faster processing speed compared to the current practice with sub-200 fs IR pulses. The refractive index contrast is comparable to the values reported for infrared-written waveguides, and the propagation losses, below 0.1 dB/cm, are to date among the lowest values reported for fused silica.