Spectroscopic properties and Judd–Ofelt study of Ho3+ doped alumino-silicate glasses for green laser applications

A novel Ho³⁺ ion doped alumino-silicate (SiAl) glasses with chemical composition (70-x)SiO₂ + 30Al₂O₃ + xHo₂O₃ (x ranged from 0.5, 0.8, 1.2 and 1.6 mol%, and was referred to as Ho³⁺ ions concentration) was prepared with sol–gel method. An increase in Ho³⁺ ion concentration leads to a corresponding rise in both the density and refractive index of the glass. X-ray diffraction and scanning electron microscopy analyses confirmed the amorphous nature of the prepared SiAlHo glass. Fourier transform infrared spectroscopy was used to identify the functional groups present in the glass system. The Judd–Ofelt parameters Ω_λ (λ = 2, 4, 6) were evaluated from the measured intensities of various absorption bands in these glasses and compared with those reported for other glass systems. Radiative properties—including radiative transition probabilities (A_ed), effective bandwidth (Δλ_eff), branching ratios (β_R), radiative lifetime (τ_R), total radiative transition probability (A_T), and stimulated emission cross-section (σ_P) were also analyzed for different excited states of Ho³⁺ ions. A prominent green photoluminescence emission corresponding to the ⁵S₂ + ⁵F₄ → ⁵I₈ transition was observed at 547 nm. The photoluminescence spectra revealed the quenching of luminescence intensity beyond 1.2 mol% of Ho³⁺ ion concentration in alumino-silicate glasses. The greenish-yellow region was displayed in the estimated CIE color coordinates for different concentrations of Ho³⁺ ions doped alumino-silicate glasses. Therefore, the SiAl glass matrix doped with 1.2 mol% Ho³⁺ emerges as a promising candidate for green light-emitting applications.