We have demonstrated that optical waveguides can be successfully written in fluorozirconate glasses (ZBLAN) by focusing an 800 nm femtosecond laser with a repetition rate of 200 kHz through a microscope objective. We measured the effects of the writing conditions on the refractive index and core size of optical waveguides. We confirmed that the diameter and refractive index of the core increase with the average laser power at a constant pulse duration
the refractive index of the core increases and the core diameter decreases as the pulse duration is decreased at a constant average laser power, and the refractive index of the core increases with the number of laser passes, while the core diameter remains unchanged. These results mean that the properties of waveguides can be controlled by adjusting the writing conditions.