Rare-earth doped Bi4Ge3O12 crystals: Advances in growth techniques and luminescence properties for laser applications

Abstract

Trivalent rare-earth (RE) ion-doped Bi₄Ge₃O₁₂ (BGO) crystals exhibit exceptional potentialities for laser applications owing to their favorable emission characteristics, superior optical/thermo-mechanical properties, and non-hygroscopic nature. This review systematically summarizes recent progresses in the growth techniques and luminescence properties of RE³⁺ (Nd³⁺, Er³⁺, Tm³⁺, Ho³⁺, Pr³⁺)-doped BGO crystals. We critically analyze four dominant growth techniquess, such as Czochralski, Micro-pulling-down (μ-PD), Floating zone, and Bridgman-Stockbarger, thus highlighting their suitability for achieving high-quality single crystals. Detailed spectroscopic investigations reveal that Nd³⁺-doped BGO leads to efficient continuous-wave lasing at 1064 nm, while Pr³⁺ and Er³⁺ co-dopings enable multi-wavelength emissions spanning visible to mid-infrared regions. Challenges in suppressing non-radiative transitions and optimizing dopant concentrations for laser performance are discussed, providing a roadmap for future research in advanced optoelectronic devices.