Structure and properties of new fluoro-sulfo-phosphate laser glasses

Abstract

<p indent=0mm>Rare-earth-doped fluoro-sulfo-phosphate (FSP) glass is characterized by excellent spectroscopic properties and high thermal and chemical stabilities. Therefore, it is a potential candidate for laser glass and high-gain active optical fiber matrix. However, the underlying contributions of compositional variations to the structure and properties of FSP glass systems are still indistinct owing to their complex mixed-anion nature. Herein, the glass-forming region, structure, physical, and luminescent properties of several FSP glasses are characterized. The results show that FSP glasses possess the advantages of fluoro-phosphate glasses such as high rare-earth ion solubility, low refractive index and phonon density of states. Meanwhile, the mixed-anion structure improves the thermal and chemical stabilities, elastic modulus and spectroscopic parameters. The fabricated FSP samples have good glass-forming ability, low nonlinear refractive index (minimum: <sc>1.2×10⁻¹³ esu</sc>), good thermal stability (∆<italic>T</italic>_max=181°C), chemical stability (DR_min=<sc>0.7×10⁻⁷ g cm⁻² min⁻¹</sc>) and relatively high elastic modulus (<italic>E</italic>_max<sc>=68.8 GPa).</sc> The maximum emission cross-section of Nd³⁺:⁴F_3/2 →⁴I_11/2 is <sc>3.3×10⁻²⁰ cm²,</sc> effective linewidth is <sc>32.1 nm,</sc> lifetime is <sc>372 μs</sc>, and FOM and gain bandwidth are <sc>1.2×10⁻²³ s cm²</sc> and<sc>105.9×10⁻²⁷ cm³,</sc> respectively. These results are higher than those of phosphate or fluoro-phosphate laser glasses, indicating the broad application prospects of FSP glasses in laser glass, fiber lasers and amplifiers.