Optical waveguides created by high energy O or F irradiation of Yb:Ca3(Nb/Ga)5O12-type disordered laser single crystals

Lanthanide-doped Ca 3 (Nb/Ga) 5 O 12 -type disordered single crystals are promising media for high-power lasers with ultrashort pulse durations. In this work, planar optical waveguides in lithium-modified Yb:Ca 3 (Nb/Ga) 5 O 12 single crystals have been fabricated by O or F room temperature irradiations using 20 MeV of energy and a fluence of 1 × 10 15 at/cm 2 . The produced waveguides show 7 dark modes in the O case and 6 dark modes in the F one, monitored at λ = 632.8 nm. Light confinement is induced by a ≈3–4% drop of the refractive index at ≈4–4.5 µm of depth, which is primarily associated to electronic damage for both irradiations. The irradiation induces some crystal colouration that is largely eliminated by air annealing in the 150–600 °C temperature range. This post-irradiation annealing reduces the waveguide propagation losses at λ = 632.8 nm of F-irradiated samples down to 1.8 dB/cm while maintaining the spectrally broad nature of the Yb 3+ fluorescence.