Emission and Absorption Cross Sections of Photorefractive-Damage-Resistant Locally Er-Mg-Doped Near-Stoichiometric Strip Waveguides

摘要

We have measured the polarized visible and near-infrared, and unpolarized mid-infrared (2.7 μm) emission spectra of photorefractive-damage-resistant locally Er-Mg-doped near-stoichiometric (NS) Ti:Mg:Er:LiNbO₃ strip waveguide, fabricated on an X-cut initially congruent LiNbO₃ substrate in sequence by local Er doping in air, Mg-Ti pre-diffusion in wet O₂ and post Li-rich vapor transport equilibration treatment. From the measured emission spectra, the emission and absorption cross section spectra were calculated based upon McCumber theory. The spectroscopic features are discussed in comparison with the spectra recorded from the area outside the waveguide, and with the previously reported results of bulk-doped NS Er:Mg:LiNbO₃ crystals and congruent Er:LiNbO₃ bulk material or Ti:Er:LiNbO₃ waveguide structure. The results show that the spectra of the NS waveguide are traditional and reveal small differences from those spectra outside the waveguide in spectral shape, polarization dependence, as well as cross section values. In contrast, the cross section values of the NS waveguide show considerable differences from those of bulk-doped NS material and congruent bulk material or waveguide structure. The 552, 673, 996, and 1531 nm emission lifetimes of the Er3+ ions outside the waveguide were also measured, and found to be comparable to the results of the bulk-doped NS crystal and the congruent bulk material or waveguide structure.