Pr3+ doped Al2O3–CaO based glasses were excellent candidate optical gain mediums for visible solid-state lasers due to its wide transmittance region and excellent mechanical properties. However, poor ...glass-forming ability limited its further application in visible fiber laser. In this work, B2O3, GeO2, Ga2O3 were employed for modifying the glass-forming ability and lowing the melting temperature of the Al2O3–CaO based glasses. By introducing 15 mol% GeO2 and Ga2O3, the thermal stability ΔT were enlarged to be 199 and 264 °C, respectively. The influence of glass composition on the fluorescence characteristic of Pr3+ were systematically investigated. For lower doping concentration, different multiphonon relaxation rare of 3P0 and 1D2 energy levels accounting for the different fluorescence spectra of Pr3+ doped Al–Ga, Al–Ge and Al–B glasses, while for the higher doping concentration, cross relaxation processes lead to the fluorescence was gradually dominated by the transition of 3P0 with increasing Pr3+ concentration.
Abstract
Cross-relaxation among neighboring emitters normally causes self-quenching and limits the brightness of luminescence. However, in nanomaterials, cross-relaxation could be well-controlled and ...employed for increasing the luminescence efficiency at specific wavelengths. Here we report that cross-relaxation can modulate both the brightness of single upconversion nanoparticles and the threshold to reach population inversion, and both are critical factors in producing the ultra-low threshold lasing emissions in a micro cavity laser. By homogenously coating a 5-μm cavity with a single layer of nanoparticles, we demonstrate that doping Tm
3+
ions at 2% can facilitate the electron accumulation at the intermediate state of
3
H
4
level and efficiently decrease the lasing threshold by more than one order of magnitude. As a result, we demonstrate up-converted lasing emissions with an ultralow threshold of continuous-wave excitation of ~150 W/cm
2
achieved at room temperature. A single nanoparticle can lase with a full width at half-maximum as narrow as ~0.45 nm.
Light and spins in rare-earth doped garnets Uspenskaya, Yulia A.; Edinach, Elena V.; Gurin, Alexandr S. ...
Journal of luminescence,
November 2022, 2022-11-00, Letnik:
251
Journal Article
Recenzirano
Spin-dependent optical properties of garnet crystals and garnet based ceramics, doped with cerium and also, along with cerium, co-doped with gadolinium and/or terbium, were studied by the method of ...optically detected of magnetic resonance by monitoring luminescence. The intensity of photoluminescence excited by circularly polarized light in the absorption bands of Ce3+ proved to be useful for selective monitoring of the population of the spin sublevels of the Ce3+ ground state. It was shown that due to cross-relaxation between the cerium and gadolinium electron spin systems the intensity of Ce3+ emission can be used to detect magnetic resonance of Gd3+. High-frequency EPR allowed finding a family of non-Kramers Tb3+ centers in yttrium aluminum garnet crystals. The influence of the magnetic resonance of Tb3+ on the luminescence of Ce3+ was observed. This suggests a coupling between the Tb3+ and Ce3+ systems, which are promising for coherent information processing. In irradiated crystals and ceramics of cerium-doped gadolinium-gallium garnet, magnetic field stimulation of the recombination of radiation defects was found, that is, it was shown that the energy accumulated during irradiation can be released in an external magnetic field. A huge increase in the afterglow intensity in a magnetic field and magnetic memory effects of magnetic memory were explained by the influence of strong internal magnetic fields on spin-dependent recombination.
•Spin-dependent optical properties of garnet crystals and garnet based ceramics.•Magnetic resonance detected via photoluminescence of cerium.•Evidence of cross-relaxation between the spin systems of Ce3+ and Gd3+ in garnets.•The influence of the magnetic resonance of Tb3+ on the luminescence of Ce3+.•Stimulation of the recombination in gadolinium-gallium garnet by magnetic field.
Er3+ and Yb3+ doped zinc titanate (ZnTiO3) was successfully synthesized using the conventional solid-state reaction method. X-ray diffraction confirmed crystallization of an ecandrewsite ZnTiO3 of an ...undoped sample, although impurity phases from the dopants were present in the doped and co-doped samples. The surface analysis showed a morphology composed of agglomerated irregular shaped particles. The energy band gap of ZnTiO3 was affected by the incorporation of different concentrations of rare-earth dopant ions. After irradiating the ZnTiO3:Er3+,Yb3+ phosphors with a 980 nm laser beam, the phosphor displayed up-converted photoluminescence emission in the visible range of the electromagnetic spectrum. The emission mostly consisted of green and red bands of Er3+ ions with peaks located at 527, 545 and 665 nm. Co-doping with Yb3+ ions proved effective in enhancing the luminescence intensity of the Er3+ ion emission, through an energy transfer mechanism.
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•A single phase of ZnTiO3 was obtained via solid state reaction.•Energy Transfer between Yb3+ ions and Er3+ was confirmed.•It was confirmed that the energy transfer involved a single photon process.
In this work, the spectroscopic properties of Dysprosium doped lithium-bismuth-borate glasses were investigated for different photonic and lasing applications. The photon absorption was observed in ...Uv–Vis–NIR region. Using Jud-Ofelt analysis the electric and magnetic dipole contribution were calculated to determine the parameters (Ω = 2, 4, 6), radiative lifetime and branching ratios of BBiLDy15 glass. The visible luminescence spectra at 482, 576, 663 and 772-nm correspond to transitions 4F9/2 → 6HJ (J = 15/2, 13/2, 11/2, 9/2) under λex = 350 nm were observed. The lasing parameters like stimulated emission cross section (5.45 × 10−22 cm2) and experimental branching ratio (61%) of the BBiLDy1.5 glass were determined from the visible transitions in the PL-emission spectra. The decrease in life time value of glass samples was observed that was attribute to the energy transfer via resonance energy transfer (RET) from host matrix to luminescence centers. The CIE chromaticity color co-ordinates, CCT results and the emission cross section for the visible transitions emphasizing the capacity of BBiLDy glass samples as potential material for white light emitting diodes and visible laser application.
•Dy3+ activated bismuth borate glasses were synthesized by melt-quenching technique.•Luminescence properties were investigated for white light emission.•JO-Analysis were performed to analyze the spectroscopic properties.•Lasing parameters were evaluated.•White light emission was confirmed from CIE diagram.
Novel thermometry strategy by utilizing synergistic effect of dual-wavelength lasers to manipulate the electron thermal distribution is proposed, which shows good temperature detection accuracy and ...signal discriminability in the physiological temperature range.
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•A novel thermometry strategy utilizing synergistic effect of dual-wavelength lasers.•A thermometry strategy going beyond limitation of the conventional TCL strategy.•The established T-sensitive electronic relation between Er3+:4S3/2 and Er3+:4F9/2.•High sensitivity and spatial resolution in the physiological temperature range.
Conventional upconversion thermometry strategy, based on the thermally coupled levels (TCL) of lanthanide ions, confronts a dilemma in simultaneously achieving high absolute/relative temperature (T) sensitivities (Sa and Sr) and good signal discriminability. Herein, a novel thermometry strategy by utilizing the synergistic effect of dual-wavelength lasers to manipulate electron thermal distribution is proposed to go beyond the limitation of the TCL-based strategy. In the case of NaGdF4: 20%Yb3+, 2%Er3+ nanoparticles upon 980 & 1530 nm dual-excitation, it is found that more efficient utilization of excited photons results in a higher electron concentration in ladder-like energy levels of Er3+, owing to the diverse pumping routes, which increases transition rate of the T-dependent phonon-assisted cross-relaxation process, and in turn establishes a thermally-sensitive electronic connection between Er3+: 2H11/2,4S3/2 and Er3+: 4F9/2. Remarkably, not only a highest record value of Sa (0.0365 K−1) for the Er3+ doped host materials in the physiological temperature range (303–343 K) is achieved, but also a high Sr (1.29% K-1) and an excellent signal discriminability (Δλ = 112 nm) are obtained. Combining a much intensified upconversion (UC) signal and a good size/shape homogeneity in nanometer scale, the investigated NaGdF4: 20%Yb3+, 2%Er3+ upon dual-wavelength excitation is potentially applicable in the intracellular thermal sensing and imaging. This work exploits an effective way to develop high-performance T-sensors, and the proposed thermometry strategy can be extended to surges of the other lanthanide ions doped systems pumped by multiple-wavelength lasers.
Traditionally, NaYF4 and glass-based materials are considered the most efficient upconversion materials. However, those materials may show signs of thermal warping or risks of fracture during ...long-term service life in extreme environments. In contrast, SiAlON ceramics preserve their spectral and physical integrity during continuous use due to their ultra-low thermal expansion coefficient (∼3.0 × 10−6/K) even at extreme temperatures. Here, we investigate the upconversion photoluminescence properties of Ho and Yb co-doped SiAlON (Ho/Yb-SiAlON) ceramics, prepared by hot-press method, at room temperature and at high temperature (298–1023 K). At room temperature, Ho/Yb-SiAlON ceramics show intense red upconversion emission under 980 nm excitation. At the high-temperature range, the spectral shift is absent in Ho/Yb-SiAlON indicating that the SiAlON ceramics have high-temperature spectral stability, which may be attributed to the low thermal expansion coefficient of SiAlON ceramics. Ho and Yb concentration-dependent spectra show an anomalous upconversion emission behavior. It is found that a higher sensitizer and low activator concentration combination is not always an ideal choice for sensitized luminescence in SiAlON ceramics which is in stark contrast to the common understanding of sensitized luminescence. The mechanism involving the dominant cross-relaxation process has been proposed to explain the observed anomalous upconversion behavior.
Peculiarities of the Overhauser effect for arsenic atoms in silicon in a strong magnetic field at low temperatures are considered. Dynamic equations describing the change in the electron paramagnetic ...resonance (EPR) signal at times exceeding the spin relaxation time have been obtained and solved. Under these conditions, the EPR signal intensity dependence on the pumping time is governed by the rate of the nuclear polarization. It is shown that the degree of nuclear polarization can reach significant value even for relatively weak pumping, and the times of establishment of nonequilibrium nuclear polarization differ significantly from the cross-relaxation time.
•Enhancement of dynamic nuclear polarization (DNP) in high magnetic fields.•DNP stabilization time is related to cross relaxation time but not equals to it.•Cross relaxation time is governed by direct acoustic photon transitions.
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Two-dimensional NOE (nuclear Overhauser effect) NMR spectroscopy was employed to investigate the dynamic properties of water within lyotropic bicontinuous lipidic cubic phases (LCPs) ...formed by monoolein (MO). Experiments observed categorically different effective residence times of water molecules: (i) in proximity to the glycerol moiety of MO, and (ii) adjacent to the hydrophobic chain towards the hydrocarbon tail of MO, as evidenced by the opposite signs of intermolecular NOE cross peaks between protons of water and those of MO in 2D 1H–1H NOESY spectra. Spectroscopic data delineating the different effective residence times of water molecules within both the gyroid (QIIG) and diamond (QIID) phase groups corresponding to hydration levels of 35 and 40 wt%, respectively, are presented. Additionally, an increase in effective residence time of water molecules in proximity to the glycerol moiety of MO in LCPs was observed upon storage at ambient temperature and in the presence of an additive lipid, cholesterol. Atom-specific NOE build-up curves for protons of water and those of MO are also given. The results presented herein provide new insight into the physicochemical properties and behaviour of water in LCPs, and demonstrate an additional avenue for experimental study of water–lipid interactions and hydration dynamics in model membranes and nanomaterials using 2D NOE NMR spectroscopy.
A Yb3+ free self-sensitized Er2WO6 phosphor has been synthesized via a solid-state reaction method. The phosphor material, Er2WO6, has a monoclinic crystal structure with space group P2/c (13). The ...deconvoluted high-resolution X-ray photoelectron spectra of all the core elements in the Er2WO6 phosphor material were explored. The highly resolved absorption peaks in the ultra-violet, visible and near-infra-red (NIR) regions of the diffuse reflectance spectrum were due to the Stark-splitting of the 4f energy levels of the Er3+ ions. Under 980 nm NIR laser excitation, the Er2WO6 phosphor showed an intense up-converted red emission at 677 nm due to the 4F9/2 → 4I15/2 transitions of the Er3+ ions. The cross-relaxation and resonance energy transfer process involved in the key intermediate 4F3/2 and 4F5/2 levels of the Er3+ and their role in generating red emissions were investigated. The laser pump power versus upconversion intensity plot showed a slope with an n value <1 and the possible reasons behind this behavior were investigated. The photoluminescence properties of the Er2WO6 phosphor in the visible and NIR region were further analyzed. The potential application of the phosphor as a marker in latent fingerprint detection was also evaluated.
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