Crystal growth and spectroscopic investigations of Dy: YAlO₃ and Dy,Tm: YAlO₃ crystals for ∼3 μm laser application

Dy³⁺:YAP and Dy³⁺,Tm³⁺:YAP single crystals have been successfully obtained by Czochralski (CZ) method aiming for ∼3 μm emission. The optical absorption and emission features of both crystals were studied in detail. A narrow and weak absorption band around 800 nm as well as the up-conversion emissions under the excitation of 802 nm in Dy³⁺:YAP crystal, along with a weak ∼3 μm emission were observed, indicating that Dy³⁺:YAP crystal was not suitable for direct pumping under 800 nm excitation. Tm³⁺ ion was introduced as a sensitizer for enhancing ∼3 μm emission. It was found that co-doping with Tm³⁺ greatly improved the absorption capacity around 800 nm. And thus an enhanced ∼2.84 μm emission was realized in Dy³⁺,Tm³⁺:YAP crystal under 795 nm excitation. The energy transfer mechanisms between Tm³⁺ and Dy³⁺ ions were discussed, and high microscopic energy transfer constants between Tm³⁺ and Dy³⁺ ions were obtained, proving that Tm³⁺ ion could act as an effective sensitizer for Dy³⁺ ion in YAP crystal. Following the obtained spectroscopic results, Dy³⁺,Tm³⁺:YAP crystal could be a promising medium for ∼3 μm laser operation under 795 nm laser diode for practical applications.