Crystalline phase, profile characteristics and spectroscopic properties of Er³⁺/Tm³⁺-diffusion-codoped LiNbO₃ crystal

Er³⁺/Tm³⁺-codoped LiNbO₃ crystal was prepared by co-diffusion of stacked Er and Tm metal films coated onto surface of off-congruent, Li-deficient LiNbO₃ substrate produced by Li-poor vapor transport equilibration technique. The crystalline phase on the diffused surface was analyzed by X-ray single-crystal diffraction. The Er³⁺ and Tm³⁺ profile characteristics were studied by secondary ion mass spectrometry. The emission spectra were measured under the 980 or 795 nm wavelength excitation, and the emission and absorption cross section spectra were calculated based upon McCumber theory. The lifetimes of some emissions were measured. The results show that the Er³⁺ and Tm³⁺ ions presence is in the form of LiNbO₃ phase. Both ions obey to Gaussian profile with a diffusion depth 21.5 μm. In the codoping case, both ions keep their respective spectroscopic features of only doping case and do not affect each other. The codoping enables to combine the wavelength emissions of both ions and the resultant emission band in the telecommunication window around 1.5 μm is as wide as 150 nm, providing the possibility of S+C+L broadband amplification by employing commercial 980 and 795 nm laser diodes as the pump sources. The Er³⁺/Tm³⁺-codoped LN is a promising host material for integrated optics.