Photoluminescence And Structure Characteristics Of Er/Yb Co-doped Oxide Films And Related Optimization Theory Analysis

With the development of optical fiber communication and integrated optics technology, Er-doped waveguide amplifiers (EDWA) have attracted much attention because of their potential application in the field of integrated optoelectronics. The near-infrared luminescence of Er³⁺ ions occurs at a wavelength of 1.53 μm, corresponding to the minimum losses of silicon optical fiber. The luminescence characteristic makes the extensive application of Er-doped material in the field of integrated optoelectronics.This paper focuses on "Photoluminescence and structure characteristics of Er/Yb co-doped oxide films and related optimization analysis". The Er-doped and Er/Yb co-doped oxide films were fabricated with a radio frequency (RF) reactive sputtering method. The crystal structure and photoluminescence (PL) spectra of the films annealed at different temperature were investigated. The effect of crystal structure on the PL spectrum of Er³⁺ ion was discussed. The optical characteristic of Er-doped or Er/Yb co-doped Al₂O₃ waveguide amplifiers were studied by solving the stable state equations which govern the populations of Er³⁺ and Yb³⁺ ions in each level. The major results are summarized as following:1. Er/Yb co-doped Al₂O₃ films with various Yb concentrations were fabricated by R.F. reaction magnetron sputtering technique and the reliability of controlling Er/Yb content ratio was discussed in the fabrication. The PL measurement showed that the film with Yb/Er content ratio of 4:1 had a maximum intensity and full width at half maximum (FWHM). The film with Yb/Er 4:1 was used for the study of the annealing behavior involving structure and PL characteristics. It was found that the annealing behavior of PL spectra had a closed relationship with the structural evolution of the host material and the relationship was discussed with the positions of Er³⁺ ions in the different alumina phases. The reason that results in the variation of PL intensity and spectral shape was revealed to be the result of the variation of host material in structure.2. The annealing behavior of Er/Yb co-doped ZnO and TiO₂ films were also studied by the PL measurement and structural characterization. It was found that the Er/Yb co-doped ZnO films had PL spectra with multi-peaks structure in the range of 800 1200℃. The maximum value of PL spectrum appeared at about 1050℃. The variation in the shape of PL spectrum was observed when Er/Yb co-doped ZnO transited into a Zn₂SiO₄ phase at the temperature higher than 1100℃, but was not remarkable, indicating that the local circumstance of Er³⁺ ion in ZnO is similar to that in Zn₂SiO₄. The variation was identified to be the result of the Er-Yb-Si-0 phase due toprecipitation of Er and/or Yb from ZnO. For the Er/Yb co-doped TiCh films, the amorphous structure had a wide PL spectrum and crystallization resulted in the appearance of PL spectra with multi-peaks structure.3. By solving the population rate equation of Er3+ ions in each level at stable state, the optical gain of Er doped or Er/Yb co-doped AI2O3 waveguide was studied and optimized by considering the influence of optical loss. It was found that the optimized Er + ion concentration was dependent on the given pump power and the length of EDWA. We found that an effective way to improve the optical gain of an EDWA with a given Er3^ ion concentration was to increase the efficient pump power. The optical loss in the waveguide was one of the important reasons that limit the improvement of optical gain for an EDWA. The results suggest that the optical gain of Er/Yb co-doped AI2O3 waveguide amplifier can not be improved by increasing the annealing temperature higher than 800 °C because of the increase of optical losses.