Covalent bonding and J–J mixing effects on the EPR parameters of Er^(3+) ions in GaN crystal

The EPR parameters of trivalent Er（3＋） ions doped in hexagonal Ga N crystal have been studied by diagonalizing the 364×364 complete energy matrices. The results indicate that the resonance ground states may be derived from the Kramers doublet Γ6. The EPR g-factors may be ascribed to the stronger covalent bonding and nephelauxetic effects compared with other rare-earth doped complexes, as a result of the mismatch of ionic radii of the impurity Er（3＋）ion and the replaced Ga（3＋） ion apart from the intrinsic covalency of host Ga N. Furthermore, the J–J mixing effects on the EPR parameters from the high-lying manifolds have been evaluated. It is found that the dominant J–J mixing contribution is from the manifold 2K（15/2）, which accounts for about 2.5%. The next important J–J contribution arises from the crystal–field mixture between the ground state 4I（15/2） and the first excited state4I（13/2）, and is usually less than 0.2%. The contributions from the rest states may be ignored.

Upconversion Emission in Er^(3+) Doped Novel Bismuthate Glass

Novel Er3+-doped bismuth lead strontiam glass was fabricated and characterized, and the absorption spectrum and upconversion spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were found to be Ω2=3.27×10-20 cm2, Ω4=1.15×10-20 cm2, and Ω6=0.38×10-20 cm2. The oscillator strength, the spontaneous transition probabilities, the fluorescence branching ratios, and excited state lifetimes were also measured and calculated. The upconversion emission intensity varies with the power of infrared excitation intensity. A plot of log Iup vs log IIR yields a straight line with slope 1.86, 1.88 and 1.85, corresponding to 525, 546, and 657 nm emission bands, respectively, which indicates that a two-photon process for the red and green emission.

Er^(3+) ion concentration effect on transient and steady-state behavior in Er^(3+):YAG crystal

The effect of Er3＋ ion concentration on transient and steady-state behavior in 45-nm Er3＋ ：YAG crystal is investigated. It is shown that by changing the signal field, the coherent field and the concentration of Er3＋ ions in the crystal, the absorption, dispersion, and group index of the weak probe field can be adjusted. Also, it is found that the probe absorption occurs in the presence of population inversion and probe amplification is obtained in the absence of population inversion.

Fabrication and photoluminescence of Er-doped ZnO thin films on SiO_2/Si substrate by pulsed laser deposition

Er doped ZnO thin films were grown on Si substrates using SiO2 buffer layer by pulsed laser deposition (PLD) method. The obtained films crystallize well and show high c-axis orientation. The Er content was evidently detected by the energy dispersive X-ray spectroscopy (EDS). Upon annealing in O2 ambience at different temperatures, the films show different photoluminescence properties at 1.54 μm. The samples annealed at 700 and 850 ℃ show intense photoluminescence peaks which enhance with the annealing temperature, while no obvious luminescence peaks are observed for the as-grown samples or annealed at 500 ℃. The possible mechanism was discussed.

Effect of alkali metal oxides R_2O (R=Na,K) on 1.53 μm luminescence of Er^(3+)-doped Ga_2O_3-GeO_2 glasses for optical amplification

This paper reported the thermal stability and spectroscopic properties of Ga2O3-GeO2-Na2O-K2O （GGNK） glasses doped with Er3＋. The GGNK glasses were characterized by differential scanning calorimetry （DSC）, Raman spectra, absorption and infra- red-visible fluorescence spectra. Measured DSC result showed that these glasses possessed an excellent stability （AT=188.6 ℃）. The relationship between glass composition and Judd-Ofelt intensity parameters and other optical properties of Er3＋, such as the absorption and stimulated emission cross-sections, were clarified. Meanwhile an intense broadband 1.53μm emission with a full width at half- maximum of 51 nm and peak emission cross-section of 9.32×10^-21 cm2 of Er3＋-doped GGNK glass was obtained upon 980 nm di- ode-laser excitation. Effects of K2O replacing Na2O on the thermal stability and spectroscopic properties were investigated. It was found that the incorporation of K2O into Er3＋-doped Ga2O3-GeO2-Na2O glass could effectively improve the 1.53 μm emission luminescence. The results showed that GGNK glass might be more attractive host material for their application in C-band optical fiber amplifiers.