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Role of Yb3+ ion on the evaluation of energy transfer and cross-relaxation processes in Gd2Ce2O7: Yb3+, Er3+ phosphors
摘要： Energy transfer (ET) and cross-relaxation (CR) processes play significant roles in regulating emitting colors and intensity of upconversion (UC) materials. Calculating the coefficients in ET and CR processes can provide visual descriptions for evaluating the UC luminescence properties. Here, we find that those ET and CR processes are responsible for the color-tunable properties in Gd2Ce2O7: Yb3+, Er3+ phosphors. By solving the rate equation, mathematical expressions are established to calculate the ET and CR coefficients based on the experimental UC spectra and lifetimes. The results are benefit to evaluate the efficiencies of ET and CR processes in quantization in different Yb3+ ion concentrations doped samples. The coefficients of ET process arise from 1.05 to 7.93 × 1017 cm3s?1 while those of CR process increase from 2.69 to 72.01 × 1017 cm3s?1 with increasing the Yb3+ ion concentration, which suggest that the CR and ET processes are efficient in Gd2Ce2O7 host. Furthermore, potential temperature sensing properties are also evaluated according to the fluorescence intensity ratio of 2H11/2 and 4S3/2 levels and the maximal sensitivity (S) is achieved about 0.00337 K?1 at 503 K. This work provides an insight into the evaluation of those UC processes and reveals the capacity in color-tunable and temperature sensing aspects.
关键词： Upconversion,Mathematical expression,Cross-relaxation,Temperature sensing,Energy transfer
更新于2025-11-14 17:03:37
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Effects of spectral diffusion on the nonlinear optical properties in two- and three-state quantum systems in a four-wave mixing signal
摘要： Effects of spectral diffusion on the third-order nonlinear susceptibility for two- and three-level quantum systems, immersed in a thermal reservoir, are evaluated with a four-wave mixing (FWM) signal through the density matrix formalism. For this, inhomogeneously broadened two- and three-level quantum systems are used. In these models, the distribution of natural frequencies follows a Lorentzian function. The absorptive and dispersive nonlinear optical responses are determined for the considered quantum models. The results presented in this work show potential applications in the development of optical switches and provide a potential method to measure spectral diffusion relaxation times in three-level quantum systems.
关键词： reservoir state,three-level quantum system,Spectral diffusion,cross-relaxation,four-wave mixing
更新于2025-09-23 15:22:29
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Study of Tm-Doped Aluminosilicate Films for Integration of Lasers on a SOI Silicon Photonics Platform
摘要： Thulium-doped glass has recently been highlighted as a potential candidate for amplifiers in a new telecommunications window, due to its potential for strong gain across a broad bandwidth in the 2-micron regime. However, the use of such technology in a silicon or planar platform has received much less attention. Lack of on-chip lasers is an obstacle to progress in silicon photonics with much research focused on mounting processed III-V lasers, bonding gain material, or the deposition of gain material onto SOI wafers. Here we report the preparation and study of Tm-doped aluminosilicate glass, which has been demonstrated as an efficient laser/amplifier in fibre-technology covering a 1.7-2.1 μm window. To achieve efficient operation the Tm3+ doping concentration is typically optimised for enhancing cross relaxation energy exchange between the 3H4 and 3F4 energy levels allowing an efficient “two-for-one” pumping approach. Fluorescent emission and gain can then be achieved by pumping with readily available ~795 nm sources diode-lasers. As such we have started preliminary investigations of higher concentrations to attempt to obtain enhanced gain per unit length devices.
关键词： silicon photonics,2-micron regime,Tm-doped aluminosilicate,on-chip lasers,cross relaxation energy exchange
更新于2025-09-11 14:15:04
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Effect of High Pressure in the Luminescence of Pr <sup>3+</sup> Doped Ge <sub/>2</sub> O- PbO Glass Containing Au Nanoparticles
摘要： In this paper it was investigated the combined effect of gold nanoparticles and high-pressure densification on the luminescence of Pr3+ doped heavy metal GeO2-PbO photonic glass. Localized states related to ion-trapped exciton defects, S1 and S2, were observed at 342 and 412 nm before densification. After densification under 7.7 GPa the structure of the glass host changed irreversibly, as indicated by the infrared spectrum, refractive index and density measurements. TEM analyses indicated that the high-pressure densification induced the formation of clusters of gold nanoparticles. The modifications observed in the absorption and luminescence spectra of Pr3+ ions in the VIS-NIR range were associated to the changes in the local field surrounding the Pr3+ ions in the host glass induced by high-pressure. For excitation at 445 nm (luminescence from 3P2) and 593 nm (luminescence from 1D2), the combined effect of densification and gold nanoparticles induced an increase in the emission band at 1050 cm-1. For excitation at 488 nm (luminescence from 3P0), the combined effect resulted in a strong decrease in the emission intensities in the VIS, revealing the emergence of non-radiative processes in resonance with 3P0 state. The observed behavior was probably due to energy transfer, ion trapped exciton defects and cross-relaxation processes among the Pr3+ ions and gold nanoparticles.
关键词： cross-relaxation processes,gold nanoparticles,Pr3+ doped,high-pressure densification,energy transfer,GeO2-PbO glass,luminescence
更新于2025-09-11 14:15:04
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Tuning and enhancing the red upconversion emission of Er3+ in LiYF4 nanoparticles
摘要： The tetragonal-phased LiYF4:Yb3+/Er3+ nanoparticles with different core-shell nanostructures have been successfully synthesized by a modified solution-based method. The upconversion emissions of LiYF4: Yb3+/Er3+ nanoparticles were precisely tuned from green to red with the increase in Yb3+ concentrations under 980 nm excitation. The corresponding intensity ratios of the red and green emissions (R/G ratios) were enhanced from 0.06 to 5.33. However, the overall integral upconversion intensity of LiYF4:Yb3+/Er3+ nanoparticles clearly decreased when the Yb3+ doping concentrations were increased. For the enhancement of the red upconversion intensity and expansion of their application, two kinds of core-shell nanostructures, namely, LiYbF4:Er3+@LiYF4 and LiYbF4:Er3+@LiYbF4, were constructed through epitaxial growth at similar experimental conditions. The LiYbF4:Er3+@LiYF4 core-shell nanostructures exhibited stronger upconversion emission and higher R/G ratios than the LiYbF4:Er3+ and LiYbF4:Er3+@LiYbF4 nanoparticles. The highest R/G ratios increased to 6.27 in LiYbF4:Er3+@LiYF4 core-shell nanostructures, increasing 104-fold. The upconversion regulation and enhancing mechanism were also discussed according to the emission spectra and fluorescence lifetimes.
关键词： upconversion,LiYF4 nanoparticles,core/shell nanostructures,cross relaxation
更新于2025-09-10 09:29:36
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Ultrapure NIR-to-NIR Single Band Emission of β-PbF2: Yb3+/Tm3+ in Glass Ceramics
摘要： An ultrapure near infrared (NIR) emission entered at 800 nm upon 976 nm laser excitation (NIR-to-NIR) was observed in β-PbF2: Yb3+/Tm3+ glass ceramics (GCs). The ultrapure NIR-to-NIR single band emission originated from the 3H4 → 3H6 transition of Tm3+ with the ratio of NIR emission, and a blue band up to 9,633 was obtained. Through detailed analysis of the crystal structure and the energy transfer between Tm3+ and Yb3+, it is elucidated that the host lattice with low phonon energy cooperative with the energy mismatch results in a dramatic population of the 3H4 state as well as ultrapure NIR-to-NIR single band emission. Moreover, up-conversion (UC) emission properties and the decay lifetimes of β-PbF2: Yb3+/Tm3+ in GCs were explored thoroughly. The results illustrate that efficient cross relaxation (CR) processes between Tm3+ generate the energy redistribution in UC emission spectra, further concentrating energy to NIR emission. These two issues can be treated as crucial factors on ultrapure NIR-to-NIR single band emission in β-PbF2: Yb3+/Tm3+ in GCs. The ultrapure NIR-to-NIR single band emission through 976 nm laser excitation is advantageous for enhancing resolution and has potential application in bio-imaging fields.
关键词： Energy mismatch,Fluoride nanocrystal doped with Tm3+,Glass ceramics,Single band,Cross relaxation
更新于2025-09-09 09:28:46