Waveguide tapers fabrication by femtosecond laser induced element redistribution in glass

Here in we present the fabrication and performance of waveguide tapers produced by femtosecond laser induced element redistribution in modified phosphate glasses. More particularly, it is demonstrated that by controlling the scan velocity during the writing process it is possible to adequately tune both the size of the modified area and the refractive index contrast to produce waveguides that can cope with mode filed diameters in the range of 7-16 μm. In addition, we fabricated tapered structures through the induction of an acceleration in the laser scanning velocity, resulting in a device that can efficiently convert a wide range of mode fields. The fine control achieved over the index contrast in the range of $10^{-3}$ and $10^{-2}$ would allow the production of a wide variety of tapers that could potentially be used to couple numerous photonic devices.