Dynamics Of Upconversion Research Articles

Influence of Host Lattice Ions on the Dynamics of Transient Multiband Upconversion in Yb-Er Codoped NaLnF4 and LiLnF4 Microcrystals (Ln: Y, Lu, Gd).

Inorganic host matrices provide a tunable luminescence environment for lanthanide ions, allowing for the modulation of upconversion luminescence (UCL) properties. AREF4 (A = alkali metal, RE = rare earth) have a low phonon energy and a high optical damage threshold, making them widely used as the host matrix for UCL materials. However, the impact mechanism of alkali metal ions and lanthanide lattice ions on transient UCL dynamics in AREF4 remains unclear. This study utilized a high-power nanosecond-pulsed laser at 976 nm to excite Yb-Er codoped NaLnF4 and LiLnF4 (Ln: Y, Lu, and Gd) microcrystals (MCs). All samples exhibit multiband emission, and the transient UC dynamics are discussed in detail. Compared with LiLnF4, NaLnF4 has higher UC efficiency and red to green (R/G) ratio. Lanthanide ions (Y, Lu, and Gd) affect the energy transfer (ET) distance in Yb-Er codoped systems, thereby altering UC efficiency and the R/G ratio. The energy level coupling between Gd3+ and Er3+ prolongs the duration of the UC emission. Specifically, the red emission lifetime of NaGdF4 is five times longer than that of NaYF4. Our research contributes to exploring excellent alternative host matrices for NaYF4 in the fields of rapid-response optoelectronic devices, micro-nano lasers, and stimulated emission depletion (STED) microscopy.

Highly efficient one-photon upconversion with cooperative enhancements of photon and phonon absorption in chlorophyll plexciton hybrids

We have demonstrated greatly enhanced light harvesting and one-photon upconversion in the plexcitonic hybrids of chlorophyll molecules strongly coupled to silver nanoparticles. The enhancement factors of the instantaneous and time-average upconversion intensity of the hybrids reached maxima of 36.2 and 28.5, respectively. Furthermore, the power and temperature dependences as well as the excitation and emission dynamics of upconversion were systematically investigated, revealing that highly efficient upconversion is predominantly attributable to the one-photon anti-Stokes process. The photon and phonon absorption processes are cooperatively enhanced by plexciton resonance. Additionally, coherent plexcitonic Rabi oscillations and plexciton-enhanced triplet–triplet annihilation are also discussed.

ChemInform Abstract: Advances in the Theoretical Understanding of Photon Upconversion in Rare‐Earth Activated Nanophosphors

AbstractReview: 104 refs.

Different dynamics of ultraviolet upconversion in Tm3+:ZBLAN glass under blue laser excitation

Ultraviolet upconversion luminescence around 292nm, 350nm and 363nm in Tm3+:ZBLAN glass was observed clearly by pulsed excitation at 464nm. Upconversion dynamics was discussed in detail by an analysis of the measured intensity dependence, decay curves and excitation spectra of upconversion luminescence, from which it was clarified that upconversion luminescence around 292nm and 350nm from 1I6 level was attributed to excited state absorption, while that around 363nm from 1D2 level was attributed to energy transfer process.

Phase dynamics of continuous topological upconversion in vortex beams

The vortex emergence process as an integer order Bessel field progresses continuously onto the contiguous higher order Bessel field is studied in detail. We assess the progressive migration of phase singularities and explain the predicted increase in fractional orbital angular momentum content of the beam in terms of this gradual process.

Analysis of the dynamics of upconversion in erbium-doped transparent lead lanthanum zirconate titanate ceramic

The absorption and upconversion fluorescence spectra of Er3+ ions in Er3+ doped transparent lead lanthanum zirconate titanate(PLZT)ceramic were measured at room temperature. The radiative transition probabilities of the Er3+ ions were calculated using the absorption spectrum of Er3+ doped PLZT. Strong upconversion emission was observed in the upconversion luminescence of Er3+ doped PLZT. The green emission intensities at 540nm and 564nm were stronger than the red emission intensity at 678nm. The upconversion rate equations describing the dynamic process of the system have been deduced. The upconversion coefficients were estimated by numerically solving the rate equations and fitting the simulated curves to the measured data. The coefficients C22and C33 obtained are 091×10-18cm3/s and 1823×10-18cm3/s, respectively. The results show that evident upconvesion phenomenon can be observed in Er3+: PLZT transparent ceramics, which is consistent with our observation.

Dynamics of excited state relaxation and frequency upconversion in Tm3+ and Tm3+/Tb3+ doped ZBLAN glass

The effects of activator concentration on the relaxation of the 1I6, 1D2, 1G4 and 3H4 levels of Tm3+ were investigated by the analysis of the fluorescence decay curves in Tm3+ and Tm3+/Tb3+ doped ZBLAN glasses. UV and blue upconversion luminescence bands around 362 and 450nm were observed by 655nm laser excitation in all the samples. The upconversion mechanism was attributed to excited state absorption (ESA) by analyzing the decay profiles and the intensity dependence.

Experimental determination of the energy-transfer parameters for homogeneous upconversion in Er-doped silica

Applying a nonlinear spectroscopic technique, we accurately monitor the dynamics of the homogeneous upconversion (HUC) in Er-doped fibers. We provide the first experimental confirmation, to our knowledge, of the earlier theoretical predictions that, for low erbium concentrations, a decay of HUC-influenced excitation probability of Er ions can be well approximated by the formula describing the static HUC. By correlating the experimentally obtained HUC dynamics with the results of our analytical model in a wide range of Er concentrations, we accurately estimate energy-transfer parameters for Er-doped silica glass and experimentally assess the validity of the model.

Dynamics of energy transfer and frequency upconversion in Tm3+ doped fluoroindate glass

Blue and ultraviolet upconversion (UC) emissions at 455 and 363nm were observed from Tm3+ doped fluoroindate glasses pumped at 650nm. The time behavior of the UC signals was studied for different Tm3+ concentrations. The measurements revealed the origin of the UC process as well as allowed to quantify the interaction between Tm3+ ions. The results indicate that a two-step one-photon absorption process is responsible for the UC emissions, and dipole-dipole interaction provides the main contribution for energy transfer (ET) among active ions. The critical distance between Tm3+ ions at which the ET rate is equal to the decay rate of noninteracting Tm3+ ions was determined.

Dynamics of the Up-Conversion Emission in Holmium Doped Zblan Fiber

The dynamics of up-conversion, green emission under excitation at different infra-red wavelength in Ho3☎ doped ZBLAN fiber is reported. Under infrared, 890 nm quasi cw pumping the complicated temporal behavior of the up-conversion signal is strongly influenced by the intermediate 5I5 state cross relaxation. The mechanisms of the observed up-conversion processes are proposed and the time evolution of the 5S2 population is described by the rate equation model. Parameters of the model are determined and numerical simulations of the excited state dynamics are performed.

Spectroscopy and dynamics of upconversion in Tm 3+: YLiF 4

Spectroscopic and dynamic properties of Tm 3+: YLiF 4 as an upconversion material with blue emission are presented. Absorption, fluorescence and excitation spectra at low temperatures were used to determine the crystal field levels of all manifolds except 1S 0 of Tm 3+. The observed energy levels were fitted in a least-square analysis to determine crystal-field parameters of the S 4 site of Tm 3+ in YLiF 4 with a standard deviation of 16 cm −1 between the calculated and measured energy levels. Judd-Ofelt calculations usuing measured integrated absorption yield the intensity parameters μ 2,4,6 for Tm 3+ in YLiF 4. From these parameters, the calculated stimulated emission cross section of the 1D 2→ 3F 4 transition is 2.4 × 10 −19 cm 2, in good agreement with the measured value of 3 × 10 −19 cm 2. An estimate of the dipole-dipole interaction which gives rise to quenching of the excited state was derived from the fluorescence decay curves at different concentrations.