Microchip and ultra-fast laser inscribed waveguide lasers in Yb³⁺ germanate glass

Abstract

We report the first Yb³⁺-doped germanate waveguide laser fabricated using femtosecond direct writing. Positive refractive-index channels were inscribed in Yb³⁺ doped high refractive-index (1.85) GPGN glass with molar composition 54.5GeO₂-31PbO-4Ga₂O₃-9Na₂O-1.5Yb₂O₃, resulting in 13 mm long waveguides with a refractive-index change of ∼9×10⁻⁴. The laser performance is investigated in the unguided microchip and in the waveguide configuration. A maximum output power of ∼51 mW at 1.052 µm with a slope efficiency of ∼30% and a lasing threshold of 100 mW was achieved from the Yb³⁺: GPGN microchip laser with a 4.5 mm gain length. A maximum output of ∼15 mW at 1.069 µm with a low lasing-threshold of 83 mW was achieved from the un-optimized 24 µm core-diameter, 13 mm long Yb³⁺: GPGN waveguide laser.