Abstract

We report on Yb³⁺:CaAlGdO₄ waveguide lasers. The waveguides were fabricated by femtosecond-laser writing. This technique allows for the fabrication of compact and efficient waveguide lasers in crystalline materials such as Yb³⁺:Y₃Al₅O₁₂ [1]. Yb :CaAlGdO₄ is an established material for generating ultra-short pulses in modelocking experiments [2]. The inscription of waveguides into this material should enable the generation of ultra-short pulses at GHz repetition rates. Such a modelocked waveguide laser was previously demonstrated in Yb³⁺-doped ion exchanged glass waveguides [3]. The Yb³⁺(5.4 %):CaAlGdO₄ crystals were grown in our lab by the Czchochalski-technique. Their high optical quality was confirmed by bulk laser experiments with a 2.9 mm thick crystal in a near-concentric resonator. Pumping by an optically pumped semiconductor laser at a wavelength of 980.6 nm, we obtained a maximum output power of 2.6 W at an absorbed pump power of 4.8 W. In this configuration slope efficiencies of up to 75 % were achieved.

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