Crystal growth, spectra properties, and 2-μm laser performance of a novel “mixed” Tm3+-doped CaY0.65Gd0.35AlO4 crystal

A novel Tm ³⁺: CaY _0.65Gd _0.35AlO ₄ (Tm ³⁺ : CYGA) disordered crystal was successfully grown for the first time, to the best of our knowledge, using the Czochralski method. The optical properties and laser performance were investigated in details. Owing to the addition of Gd ³⁺ ions to the Tm ³⁺: CYA crystal, the Tm ³⁺: CYGA crystal possesses a wider Tm ³⁺ absorption and emission spectra compared with those of the Tm ³⁺: CYA and Tm ³⁺: CGA crystals. In particular, the full width at half-maximum (FWHM) of the emission spectra at approximately 2 µm for the Tm ³⁺: CYGA crystal was 221.3 nm, which is larger than those of the Tm ³⁺: CYA (200 nm) and Tm ³⁺: CGA (151 nm) crystals. Furthermore, an efficient laser operation of the Tm ³⁺: CYGA crystal at 1974 nm was achieved for the first time, with a slope efficiency of up to 31.5 %, corresponding to a maximum output power of 810 mW. The results show that Tm ³⁺ : CYGA disordered crystals have the potential to be applied in ∼ 2-μm broadband tunable lasers and ultra-short pulse lasers.