Energy transfer characteristics of Nd³⁺/Yb³⁺-codoped phospho-silicate oxyfluoride glasses for 1.0 m laser applications

Nd3+/Yb3+-codoped phospho-silicate oxyfluoride (PNSBYNd0.5Yb0.5) glasses were prepared by melt-quenching technique and the structural and photoluminescence (PL) properties were investigated. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to assess glass microstructure and dispersed elements in the glass, respectively. A high-intense and broad Raman band appeared at 1179 cm(-1) is attributed to upsilon(as) (Si-O-Si) stretching vibrations of Q(3) units owing to high-alkali (Na+) silicates and O-P-O (PO)(2-) symmetric stretching vibrations in Q(2) units. The g value of unpaired electrons in PNSBYNd0.5Yb0.5 glasses was assessed by electron spin resonance (ESR) spectra and found to be 2.0168, more significant than the standard value (2.0023). Various bismuth ionic states (Bi2+, Bi3+ and Bi5+) were related in the Bi 4f(7/2) and Bi 4f(5/2) XPS spectra; however, Bi3+ ions were dominated. From the PL spectrum, 874 nm band for the F-4(3/2) -> I-4(9/2) transition of Nd3+ ions was dominated over 1053 nm emission band perceived in PNSBYNd0.5Yb0.5 glasses due to its quasi-three-level system. Energy transfer (ET) and cross-relaxations (CR) were unveiled in Nd/Yb-doped PNSBYNd0.5Yb0.5 glasses upon 808 nm diode laser excitation. The Nd3+ emission bands 874 and 1053 nm were merged with the Yb3+ band at 975 nm due to CR and ET from F-4(3/2) -> F-2(7/2). The high intensity of the 975 nm laser may be a suitable candidate for NIR laser and amplification applications.