We report on structural, magnetic, optical, and dielectric properties of rare earth (Er and Yb)-doped ZnO nanoparticles with Na-co-doping for charge compensation by sol-gel process. The effect of doping concentration on the structural and dielectric properties of ZnO has been studied under magnetic field and UV excitation. The magnetodielectric and photodielectric effects at room temperature of doped ZnO are discussed in the light of magnetic and optical properties of Er3+ and Yb3+ ions.

We report on photo-induced magnetic effect and infrared (IR) spectroscopic behavior of colossal magnetorestive manganite La0.7Sr0.3MnO3 (LSMO) with rare earth co-doping (Er3+ and Yb3) at room temperature. X-ray diffraction shows that a structural phase transformation from rhombohedral to hexagonal with increasing Er and Yb concentrations. Photo-induced magnetoresistance showed that Er3+ and Yb+3 ions have significant influence on the magnetic and electrical ordering of LSMO under the influence of UV light. The optical excitation also shows an enhancement in the magnetotransport properties of LSMO.

We report the temperature dependence of Er optical centers in GaN epilayers prepared by metal-organic chemical vapor deposition under the resonant excitation (4 I 15/2 → 4 I 9/2) excitation using a Ti:Sapphire laser (λexc = 809 nm). High resolution infrared spectroscopy and temperature dependence measurements of photoluminescence intensity from Er ions in GaN have been performed to identify the crystal filed splitting of the first excited state, 4 I 13/2. Here, we have employed a simple approach to determine activation energies which are related to the thermal population of electrons from the lowest level to the higher level of the crystal field splitting of the first excited state.

Spectroscopic imaging and statistical analysis of NIR-to-visible upconversion luminescence (UCL) from β-NaYF4:Yb3+:Er3+ upconverting nanoparticles (UCNPs) supported on a series of random Ag nanowire aggregates reveals a density dependent UCL enhancement. Statistical analysis of the spectrally resolved upconversion images shows a non-linear dependence of upconversion luminescence enhancement with Ag nanowire surface coverage. A maximum average enhancement of 5.8× was observed for 58% surface coverage. Based on the empirically determined trend with density, it is estimated that up to 20× upconversion luminescence enhancement can be achieved at 100% surface coverage, even at high excitation intensity. This projection is commensurate with the 20× enhancement ratio observed for select locations within the imaged micro-ensemble. Time-resolved emission of the UC luminescence from UCNPs on the Ag nanowire aggregates confirms the surface plasmon effects on the UCNPs kinetics. Such Ag nanowire aggregates show potential as a scalable and relatively simple metal-enhanced upconversion substrate.

Determining upconversion parameters is of high interest in laser material development. For many materials these parameters cannot be directly measured by experimental methods. These upconversion coefficients appear as unknown parameters in the laser rate equations, which are a system of coupled nonlinear differential equations that are used to model the dynamics of population densities in different energy levels. In this paper we propose the well-established system theoretic tools pertaining to the system inversion to be applied in this case. The unknown parameters can be considered as the inputs and the fluorescence signals can be considered as the outputs of the dynamical system. Therefore the determination of the unknown upconversion rates in the system equations from the output data is a classical system inversion problem. In this paper we demonstrate how to compute the unknown coefficients in the rate equations from the experimental emission data utilizing this method.

To fabricate practical light-emitting devices, identification and minimization of nonradiative processes are necessary. In this study, an electrical measurement technique for time-resolved analyses of nonradiative processes was proposed. From the comparison between a commercial light-emitting diode (LED) and rare-earth-doped semiconductors, the technique, called electrical frequency-response analysis (FRA), revealed differences in the charge behaviors in the pn junction of bulk semiconductors and impurities. Although the charge response time constant on the order of a nanosecond realized effective recombination of the electron–hole pairs in a LED, the time constant larger than a microsecond still limited the emission intensity of the rare-earth-doped semiconductors such as Er-doped Si nanocrystals and GaAs with Er and O codopants. The energy-loss processes of the Er-doped semiconductors were investigated, and countermeasures to enhance the emission intensity were proposed.

Excitation of multiple Er3+ ions upon absorption of a single high-energy photon increases Er-related emission at 1.5 μm, and therefore enhances UV/visible-to-IR photon conversion efficiency. Here we investigate this effect for layers of Er-doped SiO2 sensitized with silicon nanocrystals by measuring the quantum yield of 1.5 µm Er-related emission. We demonstrate dramatic increase of the emission commencing for excitation energies above a certain threshold value, as the number of Er3+ ions excited upon absorption of a single incoming photon increases. By comparing differently prepared materials, we show that the actual value of this threshold energy and the rate of the observed increase of the quantum yield depend on sample characteristics – the size of Si nanocrystals and the ratio of Er3+ ions and nanocrystals concentrations.

Single phase erbium borides ErB2, ErB4, and ErB12 show Seebeck coefficients and power factors with absolute values that are significantly lower than those of a stable Er-B multi phase composite obtained through high temperature solid-solid reaction from the elements (molar ratio Er:B = 1:6). According to quantitative Rietveld analysis the composite consists of erbium diboride (1 %), tetraboride (83 %), and dodecaboride (16 %), and the measurement of the electrical conductivities, Seebeck coefficients, and thermal conductivities leads to ZT values as high as 0.53 at 830 K. Such refractory materials can be used for energy conversion in a range of high temperatures that are otherwise difficult to address.

Vanadium dioxide (VO2) is a promising material for an optical switch due to the ultrafast and reversible transition between its two phases with contrasting optical, as well as electronic, properties. Meanwhile, erbium (Er3+) has been a standard optical amplifier for the current fiber-optic communication system. Hence, a combination of the two could be expected to make an optical switch capable of simultaneous optical amplification. In the present work, the optical switching and photoluminescence of Er-implanted VO2 were successfully demonstrated. Post-implantation annealing at 800°C or above was seen crucial for the activation of the Er centers in the VO2 crystals.

The thermal conductance of a gold/water interface has been found to change as a function of the surrounding’s adhesion energy. We measure the thermal conductance of a lithographically prepared gold nanowire with a thin film nanoscale thermal sensor composed of AlGaN:Er3+. The temperature of the nanowire is measured as a function of incident laser intensity. The slope of this plot is inversely proportional to the thermal conductance of the nanoparticle/surrounding’s interface. We show that the conductance of the nanoparticle/water interface increases with the molality of the solution. This was tested with multiple solutes including NaCl, and D-Glucose. The interfacial conductance of pure water is reported to be 44 MW/m2K and the conductance saturates to 100 MW/m2K at a molality of 0.21 m.

Erbium excited state deactivation is studied for two fluorinated complexes based on N-(P,P-ditetrafluorophosphinoyl-P,P-ditetrafluorophenyl phosphinimidates and N-(P,P-dipentafluoro phosphinoyl)-P,P-dipentafluorophenyl phosphinimidates ligands. We show that the substitution of a fluorine atom in para-position by an hydrogen atom on each phenyl ring of the perfluorinated organic ligand results in a decrease in near infrared luminescence lifetimes from 800 µs to 70 µs when measured under vacuum on sublimated powder samples. These experiments show that the introduction of C-H bonds, although outside the first coordination sphere of the erbium ion, can still induce a one order of magnitude decrease in its excited state lifetime. The found lifetime however is still longer than most reported partially fluorinated complexes, which opens the way for new functionalized complexes.

Inorganic erbium-doped glasses are widely used in telecommunications due to the sharp intra-atomic 4I13/2 → 4I15/2 transition in the 4f orbital of erbium resulting in an emission at ∼ 1.5 μm, which is the low loss window of silica optical fibres. The limited erbium concentration of about 1020 ions/cm3 in inorganic erbium-doped glasses and the low absorption coefficient of the Er3+ ions, imply that relatively long lengths of fibre are required. Organic erbium complexes present higher absorption cross sections due to the photosensitization of erbium by the organic conjugated ligands and broader emission bands than those of the free Er3+ ions. Such properties open the possibility to develop compact, low power and broadband infrared emitting devices. We present the study of an organic fluorinated erbium complex exhibiting 1.5 μm luminescence lifetime of several hundreds of microseconds measured on thin film. The organic complex has been deposited by vacuum sublimation technique. This deposition method allows the realization of an erbium-doped thin film without the help of an organic polymer matrix, which is a potential source of vibrationnal luminescence quenching. We report the synthesis, the sublimation process, and the characterization of the thin films. The chemical structure of the complex is assessed by FTIR, NMR and MALDI-TOF. Chemical integrity of the thin film after vacuum deposition is determined by FTIR. The morphology of the thin film is characterized by X-ray diffraction experiments. The optical properties of the thin film are determined by spectroscopic ellipsometry, UV-Vis-NIR absorption spectroscopy and time resolved NIR photoluminescence spectroscopy.

Er doped ZnO (Er:ZnO) thin films with Er concentration from 0.1 to 3.6 at. % were prepared by dual beam ion beam sputter deposition at room temperature. Experimental results show that as Er concentration increases from 0.1 to 1.1 at. %, the resistivity of the as-deposited Er:ZnO film decreases from 560 Ω·cm to a minimum of 0.23 Ω·cm, while further increasing Er concentration to 3.6 at. % results in increase of the resistivity to 4.2 kΩ·cm. The as-deposited Er:ZnO with Er concentration of 1.1 at.% also exhibits the highest carrier concentration of 2.3×1019 cm-3. None of the as-deposited Er:ZnO films show 1.5 μm emission without post-growth annealing. Er:ZnO film with Er concentration at 0.5~1.1 at.% shows the strongest 1.5 μm emission after annealing at 700 ~ 900°C, while all the Er:ZnO film becomes semi-insulating after annealing. The discrepancy between the processing conditions for optimized carrier concentration and optimized optically activated Er ions may due to the formation of the pseudo-octahedral structure after annealing that favors the 1.5 μm emission.

Colloidal sol-gel is a common method used for the preparation of stable and homogeneous nanoparticulate sols. In this work, TiO2 and Er3+ doped-TiO2 sols (1, 2 and 3 mole % Er3+) have been prepared. The peptization time, viscosity and isoelectric point increase at higher Er3+ concentration indicating that erbium (III) delays the peptization process, increases the viscosity and adsorbs onto the surface of the TiO2 nanoparticles. When the sols of TiO2 are doped with Er3+ lower values of the band gap are obtained. After drying, in all cases, anatase was obtained as major phase although traces of brookite are also detected. The microstructure was observed by TEM and shows direct evidence that the xerogels are polycrystalline.

Two dimensional Er3+-TeO2 thin film photonics crystals (PhCs) are fabricated. These PhCs demonstrate broadband enhancement of PL emission at near Infrared (NIR). The PhC structures are written by dual beam focused ion beam (FIB). Highly uniformed patterns with smooth surfaces are observed. A pattern resolution better than hundred nanometers is achieved. PhCs arrays with photonic lattice constants from 350 nm to 1700 nm are examined in order to optimize the PL extraction efficiency. Strong photoluminescence around 1530 nm is observed by 488-532 nm lasers pumping. A confocal microscopy with spectrometer is used to capture the broadband PL signals from individual PhC array.

The emission enhancement factor and spectral dependent extraction ratio are analyzed to find the interaction between PL lightwave and PhC structures. By optimize the PhC structures, 1500 um-1560 um broadband PL is successfully converted between the PL emission layer and the external cavity. A 60 % enhancement of surface extraction efficiency is achieved when PhC with periodicity a=800 nm is applied. When photonic lattice constants a are smaller than the critical periodicity 600 nm, the PL light becomes confined inside the thin film layer. Simulation is also performed by two dimensional finite difference time domain (FDTD) calculation in order to explain the experimental observed anisotropic PL enhancements.

The broadband PL enhancement enables Er3+-TeO2 PhCs thin film as a potential light source for three dimensional integrated photonic circuits.

Locally Er3+-doped noncongruent, Li-deficient Ti:Er:LiNbO3 strip waveguide was fabricated with a technological process in sequence of preparation of Li-deficient LiNbO3 substrate using Li-poor vapor transport equilibration (VTE), Er3+, and Ti4+ diffusion in wet O2. The Li2O content change was evaluated from the measured birefringence. The Ti4+ and Er3+ profile characteristics in the waveguide were studied by secondary ion mass spectrometry. The results show that the VTE and subsequent Er3+ diffusion procedures resulted in totally ∼0.8 mol% Li2O content reduction. The Ti4+ profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of waveguide. The Er3+ profile follows also a Gaussian function. At 1130 °C, the Ti4+ surface/depth diffusivity and surface concentration are 8.5 ± 1.3/1.98 ± 0.06 μm2/h and ∼7 mol%, respectively, and the Er3+ diffusivity and surface concentration are (12.8 ± 0.3) × 10−2 μm2/h and ∼0.6 mol%, respectively.

We demonstrate Er3+ diffusivity and solubility increases in off-congruent, Li-deficient LiNbO3 crystal. Li-poor vapor transport equilibration was used to reduce Li2O content in initial congruent crystals. Local Er3+ in-diffusion was then performed in a wet O2 atmosphere. Before and after the Er3+ diffusion procedure, surface Li2O content was evaluated from measured birefringence. The results show that the Er3+ diffusion procedure resulted in 0.3–0.5 mol% Li2O content loss at crystal surface. Secondary ion mass spectrometry was used to measure the Er3+ depth profiles, from which the diffusivity and solubility are determined. It is shown that the Er3+ diffusivity is nearly doubled and the solubility increases at least 0.6 mol% as the Li2O content decreases by 1.0 mol%. From the known Li2O content reduction, the solubility increase is also predicted and the results show that the predicted data are considerably smaller than the experimental results, suggesting that the Er3+ ions occupy also the Nb5+ site, besides the Li+ site.

Si80Ge20B0.6 thermoelectric alloys with minute erbium (Er) addition were prepared by the spark plasma sintering technique. The samples with different amounts of Er additions were analyzed by x-ray diffraction, x-ray fluorescence, and x-ray photoelectron spectroscopy. The thermoelectric properties were measured from 400 to 900 K. Effects of the amount of Er addition on the thermoelectric properties of Si80Ge20B0.6 alloys were investigated. New findings indicate that the Er-added alloys have larger carrier concentrations than the pristine sample. The larger carrier concentration appears to make a significant contribution to the electrical conductivity. Seebeck coefficient decreases with the increase of carrier concentration, whereas the power factor increases with increasing electrical conductivity. It was generally believed that the scattering of phonons by carriers may result in the thermal conductivity reduction. The samples with Er addition exhibit better figure of merits than the pristine sample. The optimal ratio of Er addition is actually in the range of 0.085–0.125 at.%.

We have measured at room temperature polarized visible and near-infrared and unpolarized mid-infrared (2.7 μm) emission spectra of Er3+ in LiNbO3 (LN) crystals grown from congruent melts doped with 0.0/0.5, 0.5/0.5, and 1.0/0.5 mol%/mol% In2O3/Er2O3. From the measured emission spectra, the emission and absorption cross section spectral distributions were analyzed based on McCumber theory and discussed in comparison with those spectra of only Er-doped LN bulk material and/or Ti: Er: LN waveguide structure and with the results from the unpolarized absorption measurements. For the 530 and 1530 nm transitions, the cross section value, polarization dependence, and spectral shape all change from the only Er-doped material to the In–Er-codoped crystal and show definite In2O3 doping level effect. The 559, 673, 996, and 1530 nm emission lifetimes were also measured and used to evaluate nonradiative multiphonon relaxation rate. The calculated radiative, measured lifetimes, and multiphonon relaxation rate also show In-codoping effects.