Femtosecond laser direct inscription of 3D photonic devices in Er/Yb-doped oxyfluoride nano-glass ceramics

Abstract

The fabrication of optical waveguides by direct femtosecond laser irradiation in Er3+/Yb3+ oxyfluoride nano-glass ceramics is investigated. Following the strategy of single line irradiation, a wide range of laser parameters can be used to obtain single-mode waveguides with nearly-gaussian modal profiles, in the visible and near-infrared. Measured propagation loss is 1.6 dB/cm for the optimum parameters (0.34 μJ/pulse and 20 μm/s scanning velocity), with no annealing after irradiation, and the induced refractive index contrast is Δn∼0.006 (at 800 nm). The multi-scan technique is used to gain control of the refractive index profiles thus producing multimodal structures. The active behavior of the waveguides is induced under ∼800 nm seeding and the co-propagating guidance of the erbium emission is demonstrated. The integration of photonic elements such as Y-splitters, both in 2D and 3D, as well as Mach-Zehnder interferometers, is also shown. Results demonstrate the optimum behavior of Er3+/Yb3+ oxyfluoride nano-glass ceramics as a host material for the integration of complex active photonic devices by femtosecond laser irradiation in the low repetition rate regime.