Engineering the meta-phosphate BaO-Al2O3-P2O5 glass network for high average power (HAP) laser applications: Systematic composition modifications and SiO2 integration

abstract

The metaphosphate glasses are the preferred gain media for high-power solid-state laser applications. In the context of solid-state glass lasers, the main challenge to attain high average power (HAP) is to govern excessive thermal loading during operation. This work focuses on addressing thermal loading issues through improving thermal and mechanical properties of the meta-phosphate BaO-Al2O3-P2O5 laser glass system by engineering its molecular structure through systematic composition modifications with SiO2 incorporation. FTIR, Raman and 27 Al MAS-NMR spectroscopy indicate stronger P - O - P bridges with decreasing glass basicity and increasing [AlO4] formations beyond 12.5 mol% Al2O3. The O/P ratio increases from 3.05 to 3.43 with up to 20 mol% SiO2 in Series-A and from 3.13 to 3.49 with up to 15 mol% SiO2 in Series-B, altering the Al coordination number from 6 to 4 to maintain the glass network charge balance. Increased [AlO4] formation raises Young's modulus from 61 GPa to 73 GPa and decreases Poisson's ratio from 0.30 to 0.24. These changes enhance fracture toughness and reduce CTE. Further, SiO2 inclusion enhances thermal conductivity by increasing glass network compactness and rigidity. These modifications highlight the improved thermo-mechanical properties of the SiO2-modified Series-B glasses. Yb3+ emission cross-section rises from 0.495 x 10-20 cm2 in ABSP-A1 glass to 0.502 x 10-20 cm2 in ABSP-B1 with increased [AlO4] formation. More AlPO4-like units in ABSP-B1 increase average glass phonon energy, reducing Yb3+ fluorescence lifetime from 1062 mu s to 945 mu s, whereas SiO2 addition boosts Yb3+ fluorescence lifetime again. Lower OH- content further extends Yb3+ fluorescence lifetime in Series-B glasses with higher SiO2 content. This study underscores the intricate relationship between glass molecular structure and thermal, mechanical, and spectroscopic properties, advancing high-power silico-phosphate laser glass development.

keywords

SPECTROSCOPIC PROPERTIES; SILICOPHOSPHATE GLASSES; METAPHOSPHATE GLASS; EFFICIENT; RAMAN; NMR

subject category

Materials Science; Optics

authors

Khan, S; Chakraborty, S; Mohapatra, SK; Fernandes, HR; Annapurna, K

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

The authors express their gratitude to the Director of CSIR-CGCRI, for her support and authorization to publish this research. Sultan Khan acknowledges the financial assistance provided by the Board of Research in Nuclear Science (BRNS) , under the advisory board of the Department of Atomic Energy (DAE) , in the form of a Senior Research Fellowship. This work was partly developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC) .r LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC) .