Efficient Er3 Research Articles

3.1 μm mid-infrared luminescence in Er3+ doped ZnF2 modified aluminum fluoride glass

Herein, melt-quenching and Er3+ doping were used to synthesize fluoride glass specimens with low phonon energies (582 cm−1). These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are excited by a 980 nm laser diode, achieving a full width at half maximum (FWHM) of about 166 nm. This 3.1 μm emission intensity is enhanced by the introduction of ZnF2 to the AlF3-based fluoride glass. Up-conversion emission, strong near-infrared emission, and fluorescence lifetime are enhanced to different degrees by increasing the ZnF2 content. Moreover, the spectroscopic characteristics of the glass specimens and the highly efficient Er3+: 4S3/2 → 4F9/2 transition's energy transfer mechanism were investigated. The absorption spectra and emission spectra of these aluminum fluoride glass specimens were used to calculate their gain coefficients and maximum cross sections at 1.5 and 3.1 μm. Overall, the spectral properties of these prepared aluminum fluoride glass specimens demonstrate their high potential for use as infrared laser host materials.

Excellent upconversion luminescence and temperature sensing performance of CdMoO4:Er3+,Yb3+ phosphors.

In this paper, Er3+/Yb3+ co-doped CdMoO4 phosphors were prepared by a traditional high temperature solid state reaction method. Based on the 3D network structure of the CdMoO4 host and the efficient Er3+/Yb3+ upconversion luminescence combinations, excellent green emission properties were observed when the prepared sample is irradiated with a laser at about 980 nm. For optical temperature sensors based on the fluorescence intensity ratio (FIR), the prepared phosphors have excellent sensitivity to temperature in the range of 293 to 473 K. With increasing environmental temperatures, the absolute sensitivity of the CdMoO4:0.02Er3+,0.08Yb3+ sample reached a maximum at about 473 K (Sa = 1.388% K-1). The calculated relative sensitivity of the optical temperature sensor was Sr = 1.631% K-1 at 293 K. This is due to the sensitive thermally coupled energy levels (TCLs) of the Er3+ ions (2H11/2 and 4S3/2) in the CdMoO4 structure. Therefore, it is shown that the prepared CdMoO4:0.02Er3+,0.08Yb3+ phosphor has excellent applications in non-contact optical temperature measurement.

Assessment of SnO2-nanocrystal-based luminescent glass-ceramic waveguides for integrated photonics

For integrated photonics, waveguide structures based on rare-earth-activated glasses are potential candidates for implementing compact integrated light sources and amplifiers. However, rare-earth ions (REs) possess low absorption cross-section, and this limits the light emission and amplification efficiency. As long as the REs are involved, there are other phenomena detrimental to their luminescence quantum yield including ion-ion interactions and non-radiative relaxation processes. To solve such problems, photonic glass-ceramics can be strategic solutions. Transparent glass-ceramics combine interesting properties of both amorphous and crystalline phases and offer specific characteristics of capital importance in photonics. More important, photonic glass-ceramics can tailor and enhance the spectroscopic properties of the rare-earth ions depending on their compositions and nature. In this work, we studied SnO2-nanocrystal-based transparent glass-ceramic planar waveguides activated by rare-earths to give solutions for the problems mentioned above and enhance the rare-earth luminescence efficiency for integrated photonics. SiO2–SnO2:Er3+ planar waveguides containing 30 mol% SnO2 nanocrystals were fabricated by sol-gel method and dip-coating technique. The planar waveguides were assessed by various characterization techniques to ensure the applicability of such glass-ceramics for integrated photonics. The experimental assessment of the SiO2–SnO2:Er3+ planar waveguides focused on the key considered photonic characteristics including the structural, morphological, spectroscopic, and especially optical waveguiding properties. The photoluminescence measurements put in evidence the role of SnO2 nanocrystals as efficient Er3+ luminescence sensitizers. Moreover, the incorporation of Er3+ ions in SnO2 nanocrystals was demonstrated to reduce the effect of non-radiative relaxation processes on the luminescence of the Er3+ ions and thus led to higher luminescence efficiency. Majority of the Er3+ ions (97%) was confirmed to be imbedded in the SnO2 nanocrystals. The SiO2–SnO2:Er3+ glass-ceramic planar waveguides have confined propagation modes, step-index profile with high confinement of 82% at 1542 nm and especially, low losses of 0.6 ± 0.2 dB/cm at 1542 nm.

Efficient Er3+:4I11/2→4I13/2 radiative transition regulated by optimizing the sensitization mechanism.

A series of fluorophosphates glass codoped with active Er3+ ions and sensitizing ions of different systems were prepared to systematically study their sensitization effect in order to obtain efficient MIR luminescence. Differential scanning calorimetry curve indicates the favorable thermal stability of the glass host. A comprehensive analysis of the sensitization mechanism is given based on the synthesis considering the position and intensity of fluorescence emissions together with the lifetime of Er3+:4I13/2 active level. The results show two positive sensitization effects: the eliminating effect to the lower laser level of Er3+ active ions represented by Pr3+ ions reducing the lifetime of 4I13/2 energy level to a great extent; and improving the absorption efficiency of pumping source sensitized by Yb3+ ions. The paper has provided a mental knowledge for sensitization mechanism in rare earth multi-doped materials together with the aiming of promoting the MIR luminescence of Er3+ ions.

Spectroscopic evaluation of Er3+-to-Sm3+ energy transfer in TeO2:ZnO glass under NIR/VIS excitation

Two sets of Er3+/Sm3+ co-doped 80TeO2:20ZnO (mol%) glass samples were synthetized and their luminescence properties investigated under VIS (532 nm) and NIR (980 nm) excitation. Emissions around 530, 550, 660, 800, and 850 nm from Er3+ and 560, 600, 645, and 700 nm from Sm3+ were generated via energy down-conversion (532 nm excitation), and up-conversion (980 nm excitation). The behavior of the emitted intensities when one varied the Er3+/Sm3+ concentration ratio indicated two Er3+-to-Sm3+ energy-transfer mechanisms, also corroborated by lifetime measurements. The efficient Er3+-to-Sm3+ energy transfer was fully characterized, and was found being dependent upon the excitation mechanism.

An energy-efficient novel emerald Er3+ doped SrGdAlO4 nanophosphor for PC WLEDs excitable by NUV light

Novel down-conversion SrGdAlO4:Er3+ nanophosphors with emerald emission were synthesized efficiently with a great success through solution combustion technique. Characterizations regarding crystallographic studies and morphological attributes were practiced by the powder XRD, EDX, SEM and TEM. Refined atomic parameters and positions were calculated for optimal sample SrGd0.96Er0.04AlO4 by realizing Refinement technique. The outcomes revealed the tetragonal phase of the doped lattice with 14/mmm (139) space group and particle size of 49.5 nm. EDX confirmed the chemical composition of sample while SEM and TEM images showed the spherical shape of nano particles with their size in the range of 49–55 nm whereas the distance between fringes present in the nanosamples was calculated as 0.204 nm by HRTEM image. FT-IR spectroscopy indicated the presence of stretching vibrations of Al–O bonds in the aluminate type of host lattice by exhibiting sharp peaks at 1154 and 1074 cm−1. Photoluminescence properties were investigated by recording photoluminescence (PL) excitation and emission, decay curves and diffuse reflectance (DR) spectra. The doped nanophosphor displays the exclusive emerald emission peaks of Er3+ ion subjected to 4S3/2 → 4I15/2 transition and its optimal concentration was remarked as 4.0 mol%. The value of critical distance (Rc) came out to be 15.91 Å which induced both the dipole-dipole and electric dipole-quadrupole interrelations as the possible mechanism for concentration quenching. The detailed description of decay curves depicted the value of life time (0.29 ms) for optimized nanophosphor. DRS specified the band gap (Eg) values for SrGdAlO4 (5.50 eV) as well as SrGd0.96Er0.04AlO4 (5.47 eV). CIE coordinates confirmed the emerald emission of novel and energy efficient Er3+ doped nanophosphors which proclaims their potential uses in the PC-WLEDs as well as other opto-electronic devices.

1.2 µm and 1.5 µm near-infrared photoluminescence and visible upconversion photoluminescence in GeGaS:Er3+/Ho3+ glasses under 980 nm excitation

We report on the Er3+ ↔ Ho3+ optical interaction on the 1.2 and 1.5 µm near-infrared and visible upconversion photoluminescence in Er3+/Ho3+-co-doped GeGaS glasses at pumping wavelength of 980 nm. Since the 980 nm pumping wavelength is off resonance for Ho3+ intra-4f electronic transitions, we have utilized the Er3+ sensitization with observed efficient Er3+ → Ho3+ energy transfer. As a result, the Ho3+ 1.2 µm emission in Er3+/Ho3+-co-doped GeGaS glass has been notably improved while the intense Er3+ 1.5 µm emission has been maintained. The visible upconversion photoluminescence has been observed at 530, 550 and 660 nm and was assigned mainly to intra-4f electronic transitions within Er3+ ions. The overall upconversion photoluminescence intensity significantly increases by addition of Ho3+ ions into GeGaS:Er glass which may be explained by energy transfer processes between Er3+ and Ho3+ ions leading to population of the Er3+ upper energy levels. The Ho3+ 1.2 µm and Er3+ 1.5 µm emission has much potential in telecommunication while the intense visible upconversion photoluminescence in sensing.

Observation of efficient Er3+:4I11/2→4I13/2 transition in highly Er3+ doped germanosilicate glass

Highly rare earth（RE）ions doped glass laser materials can produce efficient single frequency mid-infrared laser. In this work, a series germanosilicate glasses with various high erbium-doping concentration (up to 4 mol%) and without concentration quenching are fabricated. Spectroscopic properties and energy transfer (ET) mechanism of efficient Er3+:4I11/2 →4I13/2 transition have been investigated in detail upon a conventional 980 nm Laser Diode. The dense structure of silicate glass can be dissolved effectively by the introduction of GeO2, which was analyzed by Raman spectra, so that the compatibility and luminous intensity of RE ions were improved. The high predicted spontaneous transition probability (Arad = 37.65 s−1) based on the Judd-Ofelt theory and large calculated emission cross section (8.8 × 10−21 cm2) are obtained. The above results indicate that these glasses are promising to be the single frequency mid-infrared laser material.

Efficient Down- and Up-Conversion Luminescence in Er3+–Yb3+ Co-doped Y7O6F9 for Photovoltaics

Samples of Er3+–Yb3+ co-doped Y7O6F9 are synthesized by solid state reaction method, and their down- and up-conversion luminescence are studied. Upon excitation into the 4F7/2 level of Er3+ at 490 nm, effective energy transfer from Er3+ to Yb3+ via cross-relaxation Er3+ (4S3/2) + Yb3+ (2F7/2) → Er3+ (4I13/2) + Yb3+ (2F5/2) occurs, splitting an absorbed high-energy photon (λ = 490 nm) into two photons (λ = 1000 and 1540 nm). Based on the changing of the lifetime of Er3+ 4S3/2 → 4I15/2 emission without and with Yb3+, the efficiency of Er3+ → Yb3+ energy transfer in Y7O6F9:1%Er3+,9%Yb3+ has been evaluated to 58%. Upon excitation at 980 nm, as the Yb3+ doping concentration increases, not only an overall increase in intensity but also an enhancement of the red (4F9/2 → 4I15/2) emission with respect to the green (4S3/2 → 4I15/2) emission were observed. Under 980 nm laser excitation with power of 20 mW, the overall integrated emission intensity in the 500–700 nm of Y7O6F9:1%Er3+,5%Yb3+ is 1.8 times higher than t...

CaTiO3:Er3+,Ni2+broadband‐sensitive upconverter: An effective way to harvest unused NIR solar irradiation for crystalline silicon solar cells

We have realized broadband-sensitive upconversion (UC) in CaTiO3:Er3+,Ni2+ that can harvest 1060–1630 nm photons, which are not utilized by present crystalline silicon (c-Si) solar cells, and upconvert to 980 nm. The Ni2+ sensitizers absorb 1060–1450 nm photons and efficiently transfer the energies to the Er3+ emitters. In addition to 1450–1630 nm photons that are directly absorbed by the Er3+ ions, 1060–1450 nm photons are also upconverted to 980 nm by the Er3+, Ni2+ codoped upconverter, leading to a more remarkably enhanced conversion efficiency of c-Si solar cells compared to conventional Er3+-only doped upconverters. Codoping with Nb5+ to compensate for the charge imbalance caused by the Ni2+ doping at the Ti4+ sites intensified the UC emission. Similarly, charge imbalance caused by the Er3+ doping at the Ca2+ sites was compensated by codoping with alkali ions (Li+, Na+, K+), resulting in a significant improvement in the UC emission intensity. Nearly 6.5-fold intense UC emission was realized in the newly developed CaTiO3:Er,Ni upconverter compared to the previously reported CaZrO3:Er,Ni one. It is explained on the basis of higher Ni → Er energy transfer efficiency and a more efficient Er3+ UC emission. If these upconverters are applied at the rear-face of a bifacial c-Si solar cell, ∼4.8% absolute efficiency improvement is possible.

Comparative study of 27 μm emission of Ho^3+ desensitized Er^3+ in tellurite and bismuth glass

Energy transfer mechanisms have been quantitatively studied in Er3+/Ho3+ codoped tellurite and bismuth glass. Upon an excitation of 980 nm, an enhanced Er3+:2.7 μm emission was observed when Ho3+ was added to tellurite glass. Using Dexter’s theory, it is clearly shown that the efficiency of Er3+:4I13/2 → Ho3+:5I7 energy transfer is higher in tellurite glass than in bismuth glass. Based on upconversion and near-infrared spectra, the cross relaxation Er3+:4I13/2 + Ho3+:5I6 → Er3+:4I15/2 + Ho3+:5F5 is comparatively effective in tellurite glass, where it depletes the population of Er3+:4I13/2 level. The excellent spectroscopic characteristics indicate Er3+/Ho3+ co-doped tellurite glass has potential application for mid-infrared laser.

Down conversion of Er3+-Yb3+ couple in Y2BaZnO5

Er3+-Yb3+ co-doped Y2BaZnO5 phosphors were synthesized via high temperature solid-state reaction method. The quantum cutting properties for Er3+-Yb3+ co-doped Y2BaZnO5 phosphors have been detailedly exploited under different wavelength excitation. Unlike in fluoride host, only the Er(4S3/2)+Yb(2F7/2)→Er(4I13/2)+Yb(2F5/2) energy transfer process in Y2BaZnO5 effectively performs the down-conversion, which can split an absorbed high-energy photon into two photons of 1000nm and 1550nm radiations. The quantum cutting properties of Er3+-Yb3+ couple in Y2BaZnO5 provides meaningful reference in search of new efficient Er3+-Yb3+ co-doped quantum cutting phosphors.

Spontaneous emission rate and optical amplification of Er3+ in double slot waveguide

The spontaneous emission (SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure have a significant effect on the SE. The double slot waveguides were fabricated by embedding two low-index Er/Yb silicate material layers into high-index silicon. The radiative efficiency of Er3+ in the double slot waveguides is found to be higher than that of the single slot waveguide, which is consistent with the theory simulation. The 0.67 dB signal enhancement at 1.53 µm in a 4.6-mm-long slot waveguide was observed pumped by 1476 nm laser. These results show the relevance of our model to study the SE processes in multilayer structures and are important for future realization of silicon-compatible active optical devices.

Efficient 1.54-μm emission through Eu2+ sensitization of Er3+ in thin films of Eu2+/Er3+ codoped barium strontium silicate under broad ultraviolet light excitation

Thin films of Eu2+/Er3+ codoped barium strontium silicate were deposited on a thermal oxide Si substrate by magnetron sputtering. Optical properties suggest that after a rapid annealing process, these films can lead to efficient Er3+ emission at 1.54μm with a lifetime of about 7.9ms. Intense 1.54-μm light emission was achieved under broad ultraviolet light excitation through efficient energy transfer from Eu2+ to Er3+. These results indicate that the Eu2+/Er3+ thin films have potential applications as low cost and compact erbium doped waveguide amplifiers pumped by LEDs.

Size-controlled Ge nanostructures for enhanced Er³⁺ light emission.

The potential of Ge nanoparticles (NPs) embedded in Al2O3 with tunable effective optical bandgap values in the range of 1.0-3.3 eV to induce enhanced Er3+ light emission is investigated. We demonstrate nonresonant indirect excitation of the Er3+ ions mediated by the Ge NPs at room temperature. Efficient Er3+ light emission enhancement is obtained for Ge NPs with large effective optical bandgaps in the range of 1.85 to 2.8 eV. The coupled Ge NP-Er emission shows a negligible thermal quenching from 10 K to room temperature that is related to Er3+ de-excitation through thermally activated defect states.

Erbium doped tellurite glasses with improved thermal properties as promising candidates for laser action and amplification

The influence of composition on the thermal stability of tellurite glasses was investigated by using differential scanning calorimetry (DSC). The studied glasses were synthesized by conventional melting quenching method. The best thermal stability and poor crystallization tendency were obtained for the glass composed of 65TeO2–15ZnO–10Na2O–5BaO–3La2O3 doped with Er2O3 (2mol %). This glass will be referred, in this article, as TZNBL: Er3+ glass.The spectroscopic properties of the above glass are investigated based on the Judd–Ofelt and McCumber theories.The calculated intensity parameters (Ω2,4,6) are compared to those obtained for Er3+ in other glasses. The radiative emission rate has been calculated for the different Er3+emitting levels. The high values of Ω4 and Ω6 confirm the results of the DSC experiment concerning the rigidity of the studied glass.Absorption, emission and gain cross section of the 4I13/2↔4I15/2 (Er3+) transition in the studied glass are reported and the results are compared to those of other glasses.The 4I13/2↔4I15/2 (Er3+) absorption and emission cross sections derived by the application of the Mc Cumber’s theory corroborate the Judd–Ofelt results.The whole of results demonstrate that the new composition leads to good thermal and mechanical properties as well efficient Er3+ absorption, emission cross sections, which make this glass as a promising candidate for laser action and amplification.

Active glass–polymer superlattice structure for photonic integration

We propose an all-laser processing approach allowing controlled growth of organic–inorganic superlattice structures of rare-earth ion doped tellurium-oxide-based glass and optically transparent polydimethyl siloxane (PDMS) polymer; the purpose of which is to illustrate the structural and thermal compatibility of chemically dissimilar materials at the nanometer scale. Superlattice films with interlayer thicknesses as low as 2 nm were grown using pulsed laser deposition (PLD) at low temperatures (100 °C). Planar waveguides were successfully patterned by femtosecond-laser micro-machining for light propagation and efficient Er3+-ion amplified spontaneous emission (ASE). The proposed approach to achieve polymer–glass integration will allow the fabrication of efficient and durable polymer optical amplifiers and lossless photonic devices. The all-laser processing approach, discussed further in this paper, permits the growth of films of a multitude of chemically complex and dissimilar materials for a range of optical, thermal, mechanical and biological functions, which otherwise are impossible to integrate via conventional materials processing techniques.

Upconversion mechanisms and thermal effects of Er3+ in Er3+ doped yttria nanocrystals

Efficient Er3+:Y2O3 phosphor is synthesized by the sol–gel method. Rate equations for Er3+ energy level populations are used to investigate pump power and temperature dependences of upconversion intensity as well as the fluorescence decay profiles. Excited state absorption cross section of Er3+4I13/2 of 6.8×10−27m2 and cross relaxation rate of 6200s−1 are determined from comparison between theoretical predictions and experimental data. In addition, it is found that effect of temperature on the phonon-assistant absorption cannot be neglected. This work provides references for the prediction of the upconversion behavior in Er3+ singly doped matrix.

Optical properties of GaInP/GaAs:Er,O/GaInP laser diodes on p-type GaAs substrates grown by organometallic vapor phase epitaxy

Optical properties of GaInP/GaAs:Er,O/GaInP double heterostructure (DH) laser diodes (LDs) grown by organometallic vapor phase epitaxy (OMVPE) were investigated. The Er-doped LDs showed laser emission of the GaAs band-edge. The threshold current density (Jth) was 3.6 kA/cm2 on the n-type GaAs substrates and 15.8 kA/cm2 on the p-type at 77 K. The Er-doped LDs on the n-type substrate showed a strong sulfur (S)-related emission in the near-infrared region. Conversely, the S-related emission was strongly suppressed in the LDs on the p-type substrates. This was achieved by preventing the incorporation of S atoms into the GaAs active layer. For the electroluminescence (EL) properties, 1.54 μm-emission from Er3+ ions was clearly observed in the Er-doped LDs on p-type substrates. The dependence of EL intensities on the current density showed that the suppression of an energy transfer from the Er3+ ion to the S-related emission was necessary for efficient Er3+ emission at the stimulated emission region of the GaAs band-edge.

Strong enhancement of Er3+ 1.54 µm electroluminescence through amorphous Si nanoparticles

The roles of amorphous Si nanoparticles in light-emitting diodes (LEDs) based on Er-dopedSi1+xO2 films (x representing the degree of Si content, and varying widely from 0 to 4.50)have been investigated. In the aspect of the LEDs’ electrical performance,it was found that the incorporation of Si nanoparticles facilitates theelectrical conductivity of the films by improving the carrier mobility. Withx increasing from 0 to 4.50, the mobility increases monotonically up to 5 times. The efficiency ofEr3+ electroluminescence(EL) at 1.54 µm can be enhanced by as much as 160 times when the degree of Si contentx is 2.00, coincident with the value at which the rate of mobility increasing versusx slows down. The fact that the maximum of EL efficiency and theslowing down of the rate of increase of mobility occur at the samex value can be explained by coalescence of Si nanoparticles starting atx = 2.