Co-Doped La ³⁺ Achieves Synergistic Regulation of Spectral Broadening and Energy Level Dynamics in Er ³⁺ :NaSrY(MoO ₄ ) ₃ Disordered Crystals

To address the narrow emission cross section of Er3+ at 1.55 μm and its low luminescence efficiency at 2.6 μm due to the “self-quenching effect”, this work proposes a strategy of co-doping with non-optically active ion La3+ to regulate the crystal structure and spectral properties. A series of disordered Er3+:NaSrY1–xLax(MoO4)3 (x = 0.2, 0.5, and 0.8) crystals were successfully grown using the top-seeded solution growth (TSSG) method. Their structures, spectra, and laser properties were characterized in conjunction with first-principles calculations. Results indicate that La3+ introduction significantly enhances crystal chemical disorder, inducing lattice expansion and phonon energy elevation. This broadens the Er3+ emission spectrum at 1.55 μm from 68.2 to 102.1 nm (fwhm). Theoretical calculations further reveal La3+’s regulatory effect on the host bandgap and electronic structure, providing microscopic insights into spectral broadening. Co-doping with La3+ effectively modulated the energy level relaxation dynamics of Er3+, alleviating the difficulty of population inversion in the 2.6 μm band. This work demonstrates the feasibility of achieving synergistic control over spectral broadening and energy level dynamics through La3+ co-doping, offering a novel approach for developing high-performance, wide-tuning, multi-band laser gain media.