3H4 Transition Research Articles

Numerical Simulation of Ultrashort Mid-IR Pulse Amplification in Praseodymium-Doped Chalcogenide Fibers

We report the design of an ultrashort pulse amplifier based on using a chalcogenide gain fiber with a praseodymium doped core for operating in the 4–5 μm range on the (3F2, 3H6 ) → 3H5 and 3H5→3H4 transitions. A detailed numerical simulation with allowance for dispersive and nonlinear effects for two pumping schemes: four-level at 1.55 μm and three-level at 2 μm with different fiber optical losses, pulse repetition rates, and central signal wavelengths is presented. The preferable case is cascade amplification on both laser transitions with overlapping emission cross sections for seeding pulses at 4.3 μm pumped at 1.55 μm. In this case, a gain of more than 30 dB can be achieved. The pulse energy can be increased from 10 pJ up to >10 nJ for the repetition rate of order 1 MHz even for the loss level of 3 dB/m. The produced ps pulses have broadband spectra with Fourier transform limitation of order 100 fs. Further amplification may be limited by fiber damage.

Photoluminescence properties of Pr3+ ion-doped YInGe2O7 phosphor under an ultraviolet irradiation

Pr3+ ion-doped YinGe2O7 phosphors are synthesized by a vibrating milled solid state reaction. There is a red shift for the excitation peak for the charge transfer transition between In3+ and O2- ion because the numbers of oxygen vacancies change the structure, which leads to a change in the crystal field. The results indicate that the emission spectra for the YinGe2O7:Pr samples under an excitation of 263nm exhibit two dominant peaks at 486 and 604nm, which are respectively assigned to the 3P0→3H4 and 1D2→3H4 transitions. The chromaticity coordinate for (Y1−xPrx)InGe2O7 phosphors varies with the Pr3+ doping concentration, from white, to greenish, to blueish. This has a potential application as a white light emitting phosphor for ultraviolet light-emitting diodes.

Luminescence properties of Pr3+ and Bi3+ co-doped NaCaTiNbO6 phosphor for red-LEDs

This paper investigates the photoluminescence properties of NaCaTiNbO6:Pr3+ and NaCaTiNbO6:Pr3+, Bi3+ phosphors. NaCaTiNbO6:Pr3+ and NaCaTiNbO6:Pr3+,Bi3+ powder were synthesized successfully by solid state reaction method. Phase purity was checked using X-ray powder diffractometry (XRD). The excitation and emission spectra were recorded to elucidate the photoluminescence properties of NaCaTiNbO6:Pr3+ and NaCaTiNbO6:Pr3+,Bi3+. Furthermore, fluorescence lifetime measurements were performed. The excitation spectra of NaCaTiNbO6:Pr3+ show a main band centered at around 357 nm. The luminescence spectra of NaCaTiNbO6:Pr3+ exhibit a red emission peak at 615 nm from the 1D2 → 3H4 transition of Pr3+ ions. With the introduction of the Bi3+ ion into NaCaTiNbO6:Pr3+, the luminescence intensity is enhanced nearly two times. Meanwhile, the absorption band edge of NaCaTiNbO6:Pr3+ is shifted from 380 to 420 nm. Thus, this study shows that the red phosphor NaCaTiNbO6:Pr3+ incorporated with Bi3+ is advantageous for light-emitting diode applications.

Luminescent properties of Pr3+-doped SrZrO3 phosphors

In this work Sr1-1.5xPrxZrO3 phosphors with different Pr3+ contents were synthesized by polymerizable complex and high-temperature solid-state methods. The samples were calcined between 700–1400°C. The crystal structure, microstructure and photoluminescence properties of the prepared powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy, respectively.The relationship between luminescent properties and the different sintering temperatures was studied. It was found that calcination at high temperature may remarkably increase the luminescence for samples synthesized by both methods. Emission spectra for all samples show dominant bands ascribed to transitions from the 3P0,1 energy levels to lower levels, particularly that one in the greenish-blue region, corresponding to the 3P0 → 3H4 transition. However, the bands ascribed to the 3P0,1 → 2S+1LJ transitions corresponding to the red spectral region are not inhibited at all, in contrast to recent reports. The samples prepared by solid state method exhibit a charge transfer band (CTB) due to the presence of Ti4+ impurities.

Influence of Mn2+ sensitizers on orange-red emission of Pr3+ ions in BaO–Al2O3–B2O3–SiO2 glass system

Emission characteristics of Pr3+ ions sensitized with different concentrations Mn2+ ions in BaO–Al2O3– B2O3–SiO2 (BaAlBS) glass host were investigated. To have some pre-understanding over the structural modifications taking place in the glass network (which may help in understanding the variations the PL emission) due to the variation in the concentration of MnO, the spectroscopic studies like IR, EPR were also undertaken. The analysis of the results of IR spectral studies have indicated a gradual increase in the degree of depolymerisation of the glass network with increase in the concentration of MnO, whereas the EPR spectral studies have revealed a gradual increase in the concentration of octahedral positions of Mn2+ ions in the glass network. The luminescence emission spectrum of Pr3+ ions (individually) doped glass when excited at 476 nm exhibited conventional emission bands due to 3P0→3H4, 3H5,3H6; 3P1→3H5,3F3 and 1D2→3H4 transitions in the visible region. The emission spectrum of Mn2+ ions (individually) doped glasses when excited at the same wavelength also exhibited a distinct emission band at about 600 nm identified as being due to 4T1g→ 6A1g octahedral transition s of Mn2+ ions. When the Pr3+ ions are codoped with Mn2+ ions, a substantial hike in the orange emission band of Pr3+ ions could be visualized. When the glasses are co-doped with 1.0 mol% of MnO, nearly 4 fold increase in the intensity of 3P0→3H6 (orange emission band) is observed. The increase is attributed to the transfer of energy from 4T1g→6A1g emission transition of Mn2+ ions to 3P0→3H6 emission transition of Pr3+ ions. The results were further quantitatively analyzed using IR and EPR spectral studies and finally concluded that Mn2+ions are efficient sensitizers in improving the orange red emission of Pr3+ions in the titled glass host.

Quantum splitting in praseodymium-doped lanthanum aluminum dimetaborate crystals at X-ray excitation

ABSTRACTMixed lanthanum-praseodymium aluminum dimetaborate and aluminum orthoborate crystals were grown. The processes of excitation energy relaxation for the crystals were compared. For praseodymium-doped lanthanum aluminum dimetaborate crystals, the effect of quantum splitting was predicted and observed experimentally: under X-ray excitation emission of two photons at 1S0 → 1D2 and 1D2 → 3H4 transitions was shown. The possibility of quantum splitting for aluminum dimetaborates can be explained by the relatively high cation-ligand distances for this lattice.

Conformational Behaviour of Azasugars Based on Mannuronic Acid.

A set of mannuronic-acid-based iminosugars, consisting of the C-5-carboxylic acid, methyl ester and amide analogues of 1deoxymannorjirimicin (DMJ), was synthesised and their pH-dependent conformational behaviour was studied. Under acidic conditions the methyl ester and the carboxylic acid adopted an "inverted" 1 C4 chair conformation as opposed to the "normal" 4 C1 chair at basic pH. This conformational change is explained in terms of the stereoelectronic effects of the ring substituents and it parallels the behaviour of the mannuronic acid ester oxocarbenium ion. Because of this solution-phase behaviour, the mannuronic acid ester azasugar was examined as an inhibitor for a Caulobacter GH47 mannosidase that hydrolyses its substrates by way of a reaction itinerary that proceeds through a 3 H4 transition state. No binding was observed for the mannuronic acid ester azasugar, but sub-atomic resolution data were obtained for the DMJ⋅CkGH47 complex, showing two conformations-3 S1 and 1 C4 -for the DMJ inhibitor.

Effect of Pr3+ ions concentration on the spectroscopic properties of Zinc telluro-fluoroborate glasses for laser and optical amplifier applications

A new series of Pr3+ ions doped Zinc telluro-fluoroborate (PrZTFB) glasses have been prepared by adding up to 2wt% Pr2O3. Spectroscopic properties were explored through X-ray diffraction, Raman, optical absorption, photoluminescence and decay measurements. The Raman spectra reveal the presence of different vibrational bonds of the borate and tellurite network(s). The bonding parameters have shown the ionic nature of the bonding Pr–X (X=O,F). The optical band gap energy and Urbach energy have been determined to understand the electronic band structure. The Judd-Ofelt parameters Ωλ (λ=2, 4 and 6) have been calculated to explore the bonding environment around the Pr3+ ions. The luminescence spectra exhibit emission bands in the visible region attributed to the 3P0→3H4, 3F2, 3F3, 3F4 and 3P1→3H5 and 1D2→3H4, 3H5 transitions and a broad near infrared emission band at around 1330nm corresponding to the 1G4→3H5 transition with a FWHM ≈70nm. The glasses lying in the reddish orange region of CIE 1931 chromaticity diagram have been found suitable for light emitting diode applications. The decay curves of 3P0 and 1D2 levels of Pr3+ exhibit non exponential behavior for all the glasses and experimental lifetime value is found to decrease while increasing the Pr3+ ions due to cross-relaxation mechanisms. The radiative parameters corresponding to the prominent 3P0→3H4, 1D2→3H4 and 1G4→3H5 emission transitions have been determined to elucidate the suitability of the studied glasses for the fabrication of photonic devices that includes laser materials and broad band optical amplifiers.

Structure and photoluminescence of polymer-derived Pr-doped SiAlON red phosphor

The praseodymium (Pr)-doped silicon based aluminum oxynitride (SiAlON) red phosphors were prepared by a novel polymer-derived method using polycarbosilane and acetylacetonates as the starting materials. The organic precursors containing Pr and Al were formed via polymer reactions at 320°C, followed by nitridizing with NH3 at 800°C for the organic-inorganic transformation, and finally by sintering under N2 at 1650°C for the crystallization. Accordingly, the chemical composition, surface morphology, crystal structure and photoluminescence property of the polymer-derived Pr-doped SiAlON phosphors were studied. The strong red emission was observed at 623nm under the excitation of 290nm with the average decay time of 30μs, corresponding to 1D2→3H4 transition. The empirical formula was determined to be Si3.0Al0.2O0.3N3.0C0.03Pr0.02, which is Si rich with trace amount of C. The main crystal phase was identified as hexagonal β-(Si,Al)3(O,N)4:Pr with a space group P63. Each Pr ion was located in the lattice along c-axis by coordinating with three nearest N/O atoms in the neighboring plane. In addition, the amorphous Si rich components were also presented. Possible impure phases, accounted for less than 5%, might include SiC, (Pr2(Al0.5Si2.5O3.5N3.5) and PrSi3N5.

Enhanced photoluminescence of the Ca0.8 Zn0.2 TiO3 :0.05% Pr3+ phosphor by optimized hydrothermal conditions.

The red-emitting phosphor Ca0.8 Zn0.2 TiO3 :Pr3+ was synthesized using an ethylene glycol (EG)-assisted hydrothermal method. The effects of additional amounts of and order of adding EG, plus hydrothermal temperature, time, and pH on the composition, morphology and optical properties of the titanate phosphors were studied. The crystalline phases of the titanate phosphors were confirmed to be constituted of a series of co-existing CaTiO3 , Zn2 TiO4 and Ca2 Zn4 Ti16 O38 compounds in various proportions that were visualized using an X-ray diffractometer (XRD). The optical properties of the phosphors were studied using photoluminescence spectra and UV-visible spectroscopy. The results show that the impurities Zn2 TiO4 :Pr3+ and Ca2 Zn4 Ti16 O38 :Pr3+ significantly contributed to the enhancement of an absorption band around 380nm. The optimum Ca0.8 Zn0.2 TiO3 :Pr3+ phosphor consisting of appropriate amounts of CaTiO3 , Ca2 Zn4 Ti16 O38 and Zn2 TiO4 in three phases was achieved by controlling the hydrothermal conditions, and the obtained red phosphor exhibited the highest red emission (1 D2 →3 H4 transition of Pr3+ ) with an ideal chromaticity coordinate located at (x=0.667, y=0.332) under 380nm excitation.

Thermal, vibrational and optical properties of PrLuO3 interlanthanides from hydrothermally-derived precursors.

PrLuO3 interlanthanides were prepared at temperatures ranging from 800 °C to 1600 °C using hydrothermally-derived precursors. The chemical reactions observed include the conversion and segregation of Pr(OH)3 and LuO(OH), respectively, into PrO2 and Lu2O3 cubic oxides below 1200 °C, followed by the production of a mixture of hexagonal P63/mmc and orthorhombic Pnma PrLuO3 phases at 1400 °C. Phase-pure orthorhombic PrLuO3 was obtained at 1600 °C, which was corroborated by Raman and micro far-infrared spectroscopic analyses. Photoluminescence, colorimetric and lifetime measurements were carried out in PrLuO3 samples. Dominant emission verified in samples calcined at 1400 °C corresponds to the hypersensitive 3P0 → 3F2 transition with a color purity of 97% (decay times of 12 μs and 3 μs), while emissions for the phase-pure samples correspond to the 3P0 → 3H6 and 3P0 → 3H5 transitions with a color purity of 94% (a single luminescence lifetime of 12 μs). The optical properties of PrLuO3 interlanthanides thereby suggest that they can be used as luminescent materials in both structural arrangements.

Spectroscopic properties of long-lifetime Tm3+ optical centers in Ca–Sr–Ba fluorides in the form of single crystals and ceramics at the 1G4–3H5 magnetic dipole allowed transition

The spectroscopic properties of new long-lifetime Tm3+ tetragonal optical centers at low (77 K) temperature were investigated using a site-selective time-resolved technique. The absorption and excitation spectra at the 3H6–1G4 transition and the fluorescence spectra at the 1G4–3H5 transition were measured in CaF2, SrF2, and BaF2 single crystals. The appearance of additional weak lines in the excitation and fluorescence spectra in hot-formed ceramics produced from the same crystals was observed. These lines were attributed to the recently observed long-lifetime tetragonal optical centers with a modified local environment formed in fluoride ceramics.

Synthesis and luminescence of Sr2Ta2O7:Pr3+: a novel blue emission, long persistent phosphor

Abstract

Photoluminescence properties of Pr3+ doped Bi2ZnOB2O6 microcrystals and PMMA-based composites

Photoluminescence properties of red-emitting Pr3+-doped Bi2ZnOB2O6 microcrystalline powder and PMMA-based composite materials were reported. Bi2ZnOB2O6:Pr3+ powders were synthesized by means of the modified Pechini method. The morphology and crystallographic structure of Bi2ZnOB2O6:Pr3+ microcrystals were investigated by XRD and HRTEM. The PMMA-based composite materials were prepared by embedding of Bi2ZnOB2O6:Pr3+ powder in the PMMA matrix. The vibrational properties of the powder and composite systems were investigated by μ-Raman spectroscopy. Emission spectra of the samples were measured under blue (451.6 nm) and UV (320 nm) excitation. Both, the powder and composite samples show enhancement of red emission (1D2 → 3H4) and quenching of greenish-blue luminescence from 3P0 level of Pr3+ ions after excitation in UV and VIS caused by the 3P0 ∼ 1D2 non-radiative relaxation of Pr3+ ion by low-lying charge transfer state and non-radiative de-excitation through Pr3+–Bi3+ energy transfer. The response of the powder and composite samples to pulsed excitation at 451.6 nm was measured by monitoring emission from the 1D2 level (595 nm/3P0 → 3H6 transition). The determined lifetimes τ1 and τ2 of the red emission at 595 nm (1D2 → 3H4 transition) of the composite are significantly longer in comparison to powder samples. Moreover, because of the good nonlinear optical properties of the Bi2ZnOB2O6 crystals and effective luminescence of the Pr3+-doped Bi2ZnOB2O6 powders and composites, they can be very useful as bi-functional materials in the new generation of optoelectronic devices.

The luminescent property and abnormal thermal quenching behavior of Pr3+ ions in novel red phosphor Ca19Mg2(PO4)14:Pr3+

A novel Pr3+ ions doped red phosphor Ca19Mg2(PO4)14:Pr3+was first synthesized and the phase purity as well as the characteristic photoluminescence property was investigated through X-ray diffraction, diffuse-reflectance and photoluminescence spectra measurement. The analysis revealed that Ca19Mg2(PO4)14:Pr3+ had strong absorption from 450 to 470nm and could exhibit red emission peaking around 610nm under 450nm excitation. The emission quenching behavior of 1D2–3H4 transitions via increasing the Pr3+ contents was investigated and the mechanism was discussed in detail. The temperature dependent emission spectra of Ca19Mg2(PO4)14:xPr3+ with different doping contents (x=0.002 and x=0.02) were studied and the abnormal thermal quenching property was investigated.

Fatigue-resistant, temperature-insensitive strain behavior and strong red photoluminescence in Pr-modified 0.92(Bi0.5Na0.5)TiO3–0.08(Ba0.90Ca0.10)(Ti0.92Sn0.08)O3 lead-free ceramics

An electric-field-induced large strain and strong photoluminescence was achieved by introducing trivalent Pr3+ as the activator into 0.92(Bi0.5Na0.5)TiO3−0.08(Ba0.90Ca0.10)(Ti0.92Sn0.08)O3 (BNT−8BCST) ceramics. Around a critical composition of 0.4mol% Pr3+, a large strain of ∼0.39% with a relatively small hysteresis compared with existing lead-free Bi-perovskite ceramics was obtained. In particular, the strain is very resistant to field cycling and thermal shock, giving the materials attractive for its exceptionally good fatigue resistance and high temperature stability. Besides the excellent electrical properties, Pr3+-modified BNT−8BCST host exhibits a strong photoluminescence with a bright red emission at 610nm assigned to 1D2→3H4 transitions of the Pr3+ ions upon a blue light excitation of 400–500nm. The photoluminescence can be enhanced through poling treatment of the samples. Moreover, samples have a superior water resistance property which almost maintaining the same photoluminescence intensity after 40h water immersion time. These results suggest the material may have potential application as a multifunctional device such as “on-off” actuator and electric field-controlled photoluminescence devices by integrating its excellent luminescence and electrical properties.

Growth and optical properties of Pr3+ doped Na3La9O3(BO3)8 crystal

Pr3+ doped Na3La9O3(BO3)8 (Pr3+:NLBO) crystals were grown by the top-seeded solution growth (TSSG) method. Powder X-ray diffraction results show that the introduction of Pr3+ does not change the structure of NLBO crystal. Pr3+ concentration was determined to be 1.21×1021ions/cm3 by inductively coupled plasma optical emission spectrometry. The refractive index was measured by using the minimum deviation method, and Sellmeier equations were fitted. The absorption and emission spectra were measured at room temperature with a (100) oriented crystal wafer. The unpolarized and polarized emission properties under the 450nm excitation were evaluated. The decay time of the 498nm emission assigned to the 3P0–3H4 transition was also measured. The spectroscopic parameters were calculated, which are consistent with the experimental results. The results indicate that Pr3+:NLBO crystal might be a promising laser material.

Cathodoluminescence emission of REE (Dy, Pr and Eu) doped LaAlO3 phosphors

Luminescence emission from rare earth (REE) ions doped materials are being of interest since can be employed as scintillators, catalysts, battery and magnetic materials, etc. We herein report on the preliminary results obtained from the cathodoluminescence (CL) properties of undoped LaAlO3 (LAO) and LaAlO3: REE3+ (REE=Dy3+, Pr3+ and Eu3+) samples synthesized by a sol-gel process based on the Pechini's method with a spray-drying technique. The samples, previously characterized by means of Environmental Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis Spectrometry, display CL spectra with well-defined peaks that could specifically be associated with the LAO structure (in the range of 300–450nm) and point defects (from 450 to 800nm) spectral regions. The observed wavebands are as follows: (i) 480 and 570 from the Dy-doped LAO correspond respectively to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions, (ii) 490–638 from the Pr-doped LAO is linked to 3P0→3H4, 1D2→3H4 transitions and (iii) 590 and 620 where the dopant Eu3+ gives rise to 5D0→7F1 and 5D0→7F2 transitions and (iv) a UV-blue broad band is associated with NBHOC in undoped LAO. Such emissions are due to the presence of the 4f electrons of rare earth ions that are shielded by the outer 5s and 5p electrons, the intra-4f emission spectra of REE that induce sharp and narrow wavebands.

Intense upconversion fluorescence in Tm 3+/Yb3+ codoped alumina lead borate glasses

The Tm3+/Yb3+ codoped alumina lead borate glasses were prepared by the conventional melt quenching technique. Optical absorption and FTIR spectra were recorded. The upconversion fluorescence spectra exhibited weak blue (480 nm) and intense red (660 nm) emissions due to 1G4 → 3H6 and 1G4 → 3H4 transitions, respectively. The results concluded that both emissions are due to three photon absorption process. It has been observed that in the upconversion efficiency increases with the increase in the concentration of Yb3+ ions. The strong red upconversion fluorescence indicate that Tm3+/Yb3+ codoped alumina lead borate glasses can be used as potential host material for upconversion lasers.

Strong red emission and enhanced ferroelectric properties in (Pr, Ce)-modified Na0.5Bi4.5Ti4O15 multifunctional ceramics

Bismuth layer-structured ferroelectric (BLSFs) ceramics of Na0.5Bi4.5−x (Pr0.5Ce0.5) x Ti4O15 (NBT-x(Pr, Ce), x = 0.000, 0.004, 0.008, 0.012) were prepared by a conventional solid-state reaction method, and the influence of (Pr, Ce) additive on the ferroelectric, dielectric, and photoluminescence properties of samples were investigated. It is found that all the samples have a bismuth oxide layered structure with a dense microstructure. After (Pr, Ce) doping, the samples showed a bright red photoluminescence. The sharp excitation peaks around 449, 480 and 491 nm correspond to the 3H4 → 3P2, 3H4 → 3P1 and 3H4 → 3P0 transition, respectively. Upon the excitation of 492 nm light at room temperature, samples show two emission bands located at 611 and 656 nm, respectively. The strong red emission band centered at 611 nm is attributed to 1D2 → 3H4 transition, and the weak red emission located 656 nm is due to the 1D2 → 3H5 transition. In addition, it is an intrinsic ferroelectric and piezoelectric material, and the enhanced ferroelectric properties were obtained by (Pr, Ce) doping. At x = 0.004, the remnant polarization 2P r reaches 13.54 μC/cm2, together with a high Curie temperature (T c = 662 °C) and activation energy of E a = 0.83 eV. As a multifunctional material, the (Pr, Ce)-modified NBT piezoelectric ceramic may be useful in white LEDs, sensor and optical-electro integration.