Erbium Emission Research Articles

Photoluminescent Er-doped As20Se80 thin films and channel waveguides produced by thermal reflow

The chalcogenide glasses are an excellent material alternative for the poorly developed optics of the mid-infrared region on integrated photonics. Their great transmission in the IR region, the outstanding non-linear optical properties, and the recently explored possibility of processing by thermal reflow have sparked considerable interest in the fabrication of micro and nano-structures with symmetric and smooth surfaces suitable for optical components. The thermal reflow nevertheless is not useful for certain glass compositions since it induces phase separation and crystallization that compromise the optical quality. Rare earth-doped chalcogenides, of great interest for the development of laser and amplifiers, are especially prone to such dehomogenization since they have shown to be difficult to synthesize and process without obtaining fluorescence quenching caused by agglomeration and phase separation. In this work, we demonstrate for the first time that under certain conditions it is possible to induce thermal reflow in Er-doped chalcogenide thin films without inducing agglomeration and extinguishing the erbium emission. The films, produced by the co-evaporation of metallic erbium and As20Se80 glass matrix, demonstrated great molecular flexibility that allows to observe thermal reflow in films with erbium concentrations up to 0.6 at%. We use this thermal reflow in doped ridge channel waveguides (produced by photolithography) to reduce the optical losses and to enhance the fluorescence properties of the material by the rearrangement of the emitting ions. Our study opens the door for the fabrication and processing of rare earth-doped chalcogenide planar devices and their future integration into photonic circuits.

Active Erbium‐Doped Silicon Nanoantenna

AbstractThe development of silicon‐based radiative nanostructures is an important step toward silicon‐based optoelectronic systems. Here an approach for the fabrication of photoluminescent Er‐doped silicon nanoantennas is demonstrated. The combination of electron beam lithography and laser annealing of a thin Er film deposited after fabrication creates an active dielectric nanoantenna operating in the standard telecommunication wavelength range (C‐band). Using the multipole decomposition method the geometrical parameters of the silicon nanoparticle when the first‐order Mie‐resonances are tuned to the erbium emission in C‐band range ( transition) is calculated. It is observed experimentally that the presence of the Mie‐resonances provides enhancement of the photoluminescence intensity up to 40% compared to the non‐resonant case. The proposed approach allows for the creation of computational optical chips compatible with existing nanofabrication technologies.

Near-infrared photoluminescence enhancement and radiative energy transfer in RE-doped zinc-silicate glass (RE = Ho, Er, Tm) after silver ion exchange

Co-doping of rare-earth-doped glasses with silver is a promising option to enhance the photoluminescence of rare-earth (RE) ions. The enhancement of the emission of erbium has been demonstrated with great effect, but the research on the effect of silver on the near-infrared luminescence of holmium- and thulium-doped glass has been scarce. We have prepared a set of zinc-silicate glass samples doped by Ho3+/Yb3+, Er3+/Yb3+ and Tm3+/Yb3+ ions and co-doped them with silver to clarify the mechanisms behind luminescence enhancement and explore the possibility of enhancing the luminescence of holmium- and thulium-doped glass. Our results show that silver dimers increase the luminescence of RE-doped glass upon excitation in the visible range via the energy-transfer mechanism. Moreover, the photoluminescence enhancement has been observed upon excitation at 975 nm due to a combination of effects such as the structural changes of a silicate matrix and the SPR effect of silver nanoparticles.

Femtosecond laser direct inscription of 3D photonic devices in Er/Yb-doped oxyfluoride nano-glass ceramics

The fabrication of optical waveguides by direct femtosecond laser irradiation in Er3+/Yb3+ oxyfluoride nano-glass ceramics is investigated. Following the strategy of single line irradiation, a wide range of laser parameters can be used to obtain single-mode waveguides with nearly-gaussian modal profiles, in the visible and near-infrared. Measured propagation loss is 1.6 dB/cm for the optimum parameters (0.34 μJ/pulse and 20 μm/s scanning velocity), with no annealing after irradiation, and the induced refractive index contrast is Δn∼0.006 (at 800 nm). The multi-scan technique is used to gain control of the refractive index profiles thus producing multimodal structures. The active behavior of the waveguides is induced under ∼800 nm seeding and the co-propagating guidance of the erbium emission is demonstrated. The integration of photonic elements such as Y-splitters, both in 2D and 3D, as well as Mach-Zehnder interferometers, is also shown. Results demonstrate the optimum behavior of Er3+/Yb3+ oxyfluoride nano-glass ceramics as a host material for the integration of complex active photonic devices by femtosecond laser irradiation in the low repetition rate regime.

Enhanced mid-infrared emission of non-oxide erbium doped fluorochloride glass

The fluorochloride glasses samples with good luminescent properties in the infrared region were successfully prepared by melt quenching method. The introduction of Cl− effectively improved the mid-infrared (MIR) luminescence of erbium-doped fluoride glass at 2.7 µm nearby. According to Judd-Ofelt theory, the increase in Ω2 after the introduction of Cl− indicates an increase in the asymmetry and covalence of the sample. X-ray diffraction (XRD), absorption spectrum, Raman spectroscopy, infrared Fourier (FTIR) and infrared fluorescence spectroscopy were specifically conducted. The emission cross section (1.04×10−20 cm2) and the absorption cross section (9.68×10−21 cm2) of the sample at 2.7 µm nearby were calculated by measurement. Therefore, non-oxide erbium-doped fluorochloride glass is a good luminescent material in the MIR band.

Erbium emission in Er:Y2O3 decorated fractal arrays of silicon nanowires

Disordered materials with new optical properties are capturing the interest of the scientific community due to the observation of innovative phenomena. We present the realization of novel optical materials obtained by fractal arrays of silicon nanowires (NWs) synthesized at low cost, without mask or lithography processes and decorated with Er:Y2O3, one of the most promising material for the integration of erbium in photonics. The investigated structural properties of the fractal Er:Y2O3/NWs demonstrate that the fractal morphology can be tuned as a function of the sputtering deposition angle (from 5° to 15°) of the Er:Y2O3 layer. We demonstrate that by this novel approach, it is possible to simply change the Er emission intensity by controlling the fractal morphology. Indeed, we achieved the increment of Er emission at 560 nm, opening new perspectives on the control and enhancement of the optical response of novel disordered materials.

Quantifying thermal barrier coating delamination through luminescence modeling

Thermal barrier coatings (TBCs) are widely used in the hot sections of gas turbine systems as they are remarkably efficient in insulating the underlying superalloys, leading to higher operating temperatures and therefore enhancing the performance of the engines. However, this benefit is only possible if the integrity of the TBC under aggressive thermo-mechanical environments is ensured. Delamination is a common but hard to detect failure mode. We present, in this work, supported by experimentation, the implementation of a modeling approach applying the Kubelka-Munk theory to provide numerical quantification of luminescence contrast and intensity due to top coat delamination in TBCs. The method relies on the drastic change in reflectivity when a delamination forms, exploiting it for high-contrast luminescence mapping. Two distinct TBC configurations containing an erbium-doped yttria-stabilized zirconia (YSZ:Er3+) layer for delamination sensing were used to validate this model. A delamination zone induced by Rockwell indentation was successfully tracked by measuring an increase of the intensity of the erbium emission line at 562 nm. Luminescence-based methods for delamination detection can provide a revolutionary non-invasive technique, with potential for both off-line and on-line engine monitoring.

A new potential green-emitting erbium-activated α-Na3Y(VO4)2 nanocrystals for UV-excitable single-phase pc-WLED applications

A potential UV-excitable green-emitting erbium-doped α-Na3Y(VO4)2 nanocrystalline phosphor has been successfully synthesized via facile citrate-based solution combustion method. The structural characterization of the sample was carried out using X-ray diffraction, TEM, HRTEM, SAED, EDS and FTIR analysis. The phosphor exhibits green emission at 523 nm and 552 nm, which correspond to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+, respectively. The energy transfer mechanism among Er3+ ions and the concentration mechanism have been studied. The optimal doping concentration of Er3+ in the α-Na3Y(VO4)2 is found to be 0.025 mol. The non-radiative interaction among Er3+ is attributed to the dipole–quadrupole interaction. The quantum yield is found to be 7.25%, and chromaticity coordinates for the optimal concentration are found to be (0.2571, 0.6707) which are close to National Television System Committee standards for green (0.21, 0.71). The lifetime of erbium emission is found to be in microsecond range. The photoluminescence studies reveal that the newly synthesized Er3+-doped α-Na3Y(VO4)2 nanocrystals would be a good choice as green emitter to be combined with previously investigated blue- and red-emitting Tm3+- and Sm3+-doped α-Na3Y(VO4)2 nanocrystals for realizing RGB phosphor.

Slow relaxation of two dimensional salen type lanthanide coordination polymer

Reactions of N,N′-bis(salicylidene)-1,2-cyclohexanediamine (H2L) with mixed lanthanide counterions of LnCl3·6H2O and Ln(NO3)3·6H2O afford four lanthanide coordination polymers, e.g. {Dy(H2L)1.5(NO3)3]·5CHCl3·CH3OH}n (1) and {[Ln(H2L)1.5(NO3)2Cl]·2CH2Cl2}n [Ln = Ho (2), Er (3) and Lu (4)]. X-ray crystallographic analysis reveals that H2L effectively function as a bridging ligand possessing two-dimensional (2D) network frameworks. Magnetic analysis reveals that complex 1 exhibits slow magnetic relaxation. The luminescence of complex 1 exhibits luminescence of the ligand, complex 2 and 3 show characteristic near-infrared (NIR) emission of holmium(III) and erbium(III) ions.

NIR‐II/III Luminescence Ratiometric Nanothermometry with Phonon‐Tuned Sensitivity

AbstractLuminescence nanothermometers are promising for noninvasive, high resolution thermographics ranging from aeronautics to biomedicine. Yet, limited success has been met in the NIR‐II/III biological windows, which allow temperature evaluation in deep tissues. Herein, a new type of phonon‐based ratiometric thermometry is described that utilizes the luminescence intensity ratio (LIR) between holmium (Ho3+) emission at ≈1190 nm (NIR‐II) and erbium (Er3+) emission at ≈1550 nm (NIR‐III) from a set of oxide nanoparticles of varying host lattices. It is shown that multi‐phonon relaxation in Er3+ ions and phonon‐assisted transfer process in Ho3+ ions play a significant role in LIR determination through channeling the harvested excitation energy to the corresponding emitting states. As a result, temperature sensitivity can be tuned by the dominant phonon energy of host lattice, thus endowing aqueous yttrium oxide (Y2O3, 376 cm−1) nanoparticles to have a relative temperature sensitivity of 1.01% K−1 and absolute temperature sensitivity of 0.0127 K−1 at 65 °C in a physiological temperature range (25–65 °C). And their temperature sensing for biological tissues is further explored and the influence of water and chicken breast on thermometry is discussed. This work constitutes a solid step forward to build sensitive NIR‐II/III nanothermometers for biological applications.

Two Series of Lanthanide Coordination Polymers and Complexes with 4′‐Phenylterpyridine and their Luminescence Properties

Two series of trivalent lanthanide and group 3 metal coordination polymers with 4′‐phenyl‐2,2′:6′,2′′‐terpyridine (ptpy) of the composition 1∞[MCl3(ptpy)] (1, M = La, Ce, Pr, Nd) and the complexes [MCl3(ptpy)(py)] (2, M = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) have been synthesized and characterized. For europium, the complex [Eu2Cl6(ptpy)2] (3) was obtained as single crystals, its dimeric structure providing potential insight into the coordination polymer formation from monomeric entities. Product series 1 and 2 were photophysically investigated in the solid state at room temperature and 77 K. Alongside with standard ion‐specific 4f–4f trivalent lanthanide luminescence in the visible and NIR (of emitters such as europium, terbium, dysprosium, neodymium, etc.), visible range emission of praseodymium, holmium, erbium, and thulium was observed, which is rarely reported for coordination compounds. It occurs in addition to their characteristic NIR emission. For complexes of series 1, an exciplex based luminescence was observed originating from ligand π‐stacking in the crystal packing.

Enhanced mid infrared emission of erbium doped fluoro-zinc glass-ceramics

Erbium doped glass-ceramics modified by different content of Zn2+ were prepared. The mid-infrared fluorescence intensity (2.7 μm) has been enhanced by Zn2+ introduction. The x-ray diffraction (XRD), FTIR and mid-infrared spectra were investigated. As the introduction of Zn2+, the crystals (ZrF4) begin to participate in glass. In addition, the size of the crystals changes with the content of Zn2+ ions. The mid-infrared emission intensity enhanced with the growth of crystals. Ω2 improved with the introduction of Zn2+, which showed higher asymmetry and covalency. Emission cross-section (1.42 × 10−20 cm2) and absorption cross-section (1.04 × 10−20 cm2) at 2.7 μm were measured. By the Judd-Ofelt theory and absorption curves, it shows that parameter.

Understanding the downconversion photoluminescence of NaLaP4O12:Er3+ phosphor

Abstract We have employed the solid-state chemical reaction to construct series of trivalent erbium ions activated NaLaP 4 O 12 (abbreviated as: NLP) phosphors. The structural investigation indicates that NLP:Er 3+ crystalline products are purely monoclinic phase with micron particles. Trivalent erbium ions with the substitution for lanthanum are successfully inserted into NLP host lattice. The UV–Vis diffuse reflectance absorption performance, doping Er 3+ content-dependent downconversion photoluminescence, content quenching mechanism were reported in this paper. Upon near UV (378 nm) excitation, yellow/yellow-green visible light with the dominant 4 S 3/2 → 4 I 15/2 emission of trivalent erbium is displayed. Yellow-green emitting NLP:2%Er 3+ sample has the maximum intensity and main luminescent peaks at 541 and 549 nm. The content quenching is related to the dipolar interaction. Additionally, the detailed investigation on CIE chromaticity coordinates, CP and CCT reveals that the title product has promising application in the field of white LEDs excited by near UV light.

Dispersion measurement of ultra-high numerical aperture fibers covering thulium, holmium, and erbium emission wavelengths

We present broadband group velocity dispersion (GVD) measurements of commercially available ultra-high numerical aperture fibers (UHNA1, UHNA3, UHNA4, UHNA7, and PM2000D from Coherent-Nufern). Although these fibers are attractive for dispersion management in ultra-fast fiber laser systems in the 2 μm wavelength region, experimental dispersion data in the literature is scarce and inconsistent. Here we demonstrate the measurements using the spectral interferometry technique covering the typically used erbium, thulium, and holmium emission bands. The results are characterized in terms of the standard-deviation uncertainty and compared with previous literature reports. Fitting parameters are provided for each fiber allowing for the straightforward replication of the measured dispersion profiles. This work is intended to facilitate the design of ultra-fast fiber laser sources and the investigations of nonlinear optical phenomena.

High sensitization efficiency and energy transfer routes for population inversion at low pump intensity in Er organic complexes for IR amplification

Organic erbium complexes have long been of interest due to their potential for using the strong absorption into the organic to sensitise the erbium emission. Despite this interest there is remarkably little quantitative information on how effective the approach is and the discussion of the energy transfer mechanism is generally vague. Here we accurately quantify the sensitisation as a function of excitation pump density and model it using a rate equation approach. As a result, we can calculate the degree of population inversion for the erbium ions as a function of the pump intensity. We demonstrate that even when we increase the erbium concentration in the films from ~10 to ~80% we find a relatively small decrease in the sensitisation which we attribute to the large (>20 Å) Förster radius for the sensitisation process. We show that we can obtain population inversion in our films at very low pump powers ~600 mW/cm2. The calculated Förster radius for the organic erbium complexes suggests design rules for energy transfer between antennas and erbium ions in molecular systems and hybrid organic-inorganic nanoparticles.

Sensitized photoluminescence of erbium silicate synthesized on porous silicon framework

Er silicate/porous silicon (PS) composites with effective sensitized erbium emission at 1.53 μm have been synthesized on the PS framework. Cross-sectional scanning electron microscopy and X-ray diffraction reveal that the PS is coated by Er silicate in composites. Indirect excitation of Er3+ ion luminescence via energy transfer from PS is confirmed. The temperature dependence of Er-related photoluminescence intensity and lifetime is investigated, which concludes a phonon-mediated energy transfer process. The combination of the PS framework and Er silicate provides a possible strategy for practical silicon-based light sources.

Removal of hydroxyl groups from Er3+/Yb3+ codoped flurotellurite glasses

In this work, we present a safe and relatively simple procedure to eliminate hydroxyl groups from Er3+ and Yb3+ codoped new flurotellurite glasses. It was shown that adding a convenient amount of BaF2 as drying agent reduced the absorption coefficient and the concentration of hydroxyl groups inside the glass samples. However, to remove efficiently water from the glasses, it was necessary to subject the samples to supplementary heat treatment in two steps. A drastic decrease of the density of hydroxyl groups accompanied with a significant enhancement of the erbium emission was observed after the heat-treatment procedure. The obtained results showed that this method might be a veritable alternative to obtain nearly water free tellurite glasses suitable for many optical devices with small sizes or thickness. However, for a good use of this procedure, we tried to elucidate what has happened at the microscopic scale for the glass taking as a guide the available explanations dealing with the removal of water from silica-based glasses.

Crystal structures and photoluminescence properties of two novel sorosilicates with an unprecedented ratio of di- and trisilicate groups: Ba2Ho10(Si2O7)3(Si3O10)2 and isotypic Ba2Er10(Si2O7)3(Si3O10)2

Ba2Ho10(Si2O7)3(Si3O10)2 and isotypic Ba2Er10(Si2O7)3(Si3O10)2 represent a new mixed-framework structure type with an unprecedented ratio of di- and trisilicate groups among silicates. The atomic arrangement features asymmetric zigzag chains of edge-sharing Ln3+O6 (Ln = Ho, Er) octahedra corner-linked by isolated Si2O7 and horseshoe-shaped Si3O10 groups in the ratio of 3:2. Single-crystal X-ray diffraction investigations yielded the triclinic space group P1¯ (no. 2), with a = 5.5494(11)/5.5360(11)Å, b = 6.8795(14)/6.6870(13)Å, c = 23.703(5)/23.691(5)Å, α = 83.60(3)/83.64(3)°, β = 88.80(3)/88.77(3)°, γ = 73.43(3)/73.38(3)°,V = 861.9(3)/835.2(3)Å3, R(F) = 0.0289/0.0559, respectively. The laser-induced photoluminescence emission of trivalent holmium und erbium in both framework silicates was studied using a dispersive single-stage spectrometer and compared to the emission spectra of other framework Ba-Er and Ba-Ho silicates. The 4S3/2→4I15/2 transition of Er in Ba2Er10(Si2O7)3(Si3O10)2 causes a photoluminescence emission in the visible green spectral range whereas its Ho representative with the 5F3→5I7 transition in the red spectral region.

Effect of ytterbium substitution on LaEr(1−x)YbxO3 optical properties

A series of LaEr(1−x)YbxO3 (x=0, 0.01 and 0.05) samples were prepared with a combustion method and characterized by FTIR, Raman spectroscopy and X-ray diffraction. The optical properties of samples were studied upon laser excitations. The upconversion emission spectra registered under excitation at 980nm show the presence of the typical erbium emission bands and that the higher intensity is given by sample with 5% of ytterbium concentration. The variation of upconversion intensity as a function of laser power of the LaEr0.95Yb0.05O3 sample reveals that two photons are implicated in the upconversion mechanism and that the lifetime of the 4S3/2→4I15/2 and 4F9/2→4I15/2 emissions of this sample is estimated to 12.3 and 97.7µs, respectively. The calculated CIE chromaticity coordinates of the phosphor samples show that the green emission is dominant, and that its intensity increases by substituting erbium with 1% or 5% of ytterbium. The effect of ytterbium concentration on optical band gap shows that the gap energy value tends to decrease from 4.25eV to 4.14eV for 0% and 5% of ytterbium concentration, respectively. The increase in intensity of green emission by adding ytterbium to LaErO3 classifies these oxides as phosphor materials that could have applications in bioimaging of cells.

Highly matched spectrum needed for photosynthesis in Ce3+/Er3+/Yb3+ tri-doped oxyfluoride glass ceramics

A series of oxyfluoride glass ceramics containing CaF2 nano-crystals tri-doped with Ce3+/Er3+/Yb3+ ions were prepared by high temperature melting method and subsequent heat treatment. The structural properties were examined by X-ray diffraction measurements. The absorption, excitation, and emission spectra of the glass ceramics were investigated. Difference in erbium emission spectra between glass and glass ceramics had been studied. The emission bands originating from the 4F9/2 state of Er3+ were enhanced when the CaF2 nano-crystal created. By down-converting the ultraviolet wavelength region (280∼400 nm) light and up-converting the near-infrared wavelength region (900∼1100 nm) light, the glass ceramics can also emit strong reddish orange emission. The emission spectra consisting of bluish violet (400∼500 nm) and reddish orange (640∼680 nm) bands match well with the action spectrum of photosynthesis and absorption spectra of chlorophylls. Our materials will be favored to promote the development of glass greenhouses for green plant.