Laser wavelength extension beyond 1.1 μm in Nd:MgO:LiNbO₃ crystal by utilizing the Stark splitting of multiple...

Lithium niobate crystal is an important multifunctional material and the miniaturization of the integrated on-chip LiNbO₃ laser device has attracted the increased attention in optoelectronic systems. Especially in the field of quantum information, rare-earth doped LiNbO₃ (e.g. Nd:LiNbO₃) crystal become one of the optimal choice for the active devices and laser generation. However, at present, Nd:LiNbO₃ crystal suffers from low conversion efficiency and the limited lasing wavelength due to the discrete Stark energy levels of Nd³⁺ ion. Herein, we proposed a multiple-site doping strategy to enrich the Stark splitting levels of Nd:LiNbO₃ laser crystals. Benefitting from the strong inhomogeneous and homogeneous broadening effect, a broad fluorescence emission beyond 1.1 μm was realized in Nd:MgO:LiNbO₃ crystal. Via a rational cavity design to suppress the lasing oscillation at 1.07-1.09 μm and amplify the weak fluorescence at long wavelength, we successfully achieved the efficient continuous-wave lasing at 1104 nm, 1108 nm, 1111 nm, and 1114 nm, respectively, corresponding to the electronic transitions (R₁→Y₄, Y₅, Y₆) at two different Nd³⁺ sites. The highest laser power at 1.1 μm was 1.41 W with a slope efficiency of 20.6%. Moreover, a tunable laser generation from 1103 to 1115 nm was also realized in Nd:MgO:LiNbO₃ for the first time. To the best of our knowledge, this result represents the first Nd:MgO:LiNbO₃ laser operating beyond 1.1 μm, indicating its great potential for optical applications in on-chip lithium niobate devices.