Transitions Of Ho Research Articles

Spectroscopic Properties of Ho<sup>3+</sup> Doped in B<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub>-SrO-Bi<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> Glasses

A series of glasses with nominal composition in (53-x)B2O3:11SiO2:34SrO:1Bi2O3:1TiO2: xHo2O3 (BSSBT) where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol% was synthesized by conventional melt quenching method. The as-prepared glasses have been investigated and reported for their physical and optical properties. The results show that, the densities and refractive index increase with increasing Ho2O3 content in the glasses. The absorption peaks of doped glasses were observed at a wavelength of around 420, 460, 480, 540, 640 and 900 nm which are assigned to 5I8 ® 5G5, 5G6, 5F3, (5F4+5S2), 5F5 and 5I5 transitions of Ho3+, respectively.

SrWO4:Ho3+, Yb3+, Tm3+ microspheres with white-light emission: synthesis and luminescence

We synthesized SrWO4:Ho3+, Yb3+, Tm3+ microspheres successfully by the solvothermal process. The samples were characterized by XRD, FTIR, SEM, and fluorescence spectrofluorometer. The XRD patterns and FTIR spectra indicate that the samples have the pure tetragonal scheelite structure. The SEM images suggest that Na-Citrate plays a key role in the formation of spherical morphology. The samples are microspheres if there is the use of Na-Citrate, whereas the samples are irregular particles if there isn’t the use of Na-Citrate. Under diode laser excitation of 980 nm, SrWO4:Ho3+, Yb3+, Tm3+ samples show blue, green, and red emissions originating from the transitions of Ho3+ and Tm3+ ions. The emission intensity of microspheres is about twice those of irregular particles. The emission shows clear dependence on pump powers. On the basis of the luminescence properties of SrWO4:Ho3+, Yb3+, Tm3+ phosphors, the possible mechanisms are speculated.

Study on structural, optical and gain properties of 1.2 and 2.0 μm emission transitions in Ho3 + doped tellurite glasses

Holmium (Ho3+) ions doped tellurite (TBZLN) glasses in the chemical composition (78−x)TeO2+4.5Bi2O3+5.5ZnO+10.5Li2O+1.5Nb2O5+xHo2O3 where x=0.05, 0.1, 0.5, 1.0, 1.5mol% were prepared by melt quenching technique and a detailed study on spectroscopic properties were reported. The characterization of prepared glasses was realized by optical absorption, fluorescence, decay profiles, X-ray diffraction (XRD), differential thermal analysis (DTA), Raman and Fourier transform infrared (FTIR) spectroscopic techniques. Absorption spectra have been analyzed by using Judd–Ofelt (J–O) theory and estimated intensity parameters, Ω2, Ω4 and Ω6, are compared with other reported glasses. The radiative properties such as radiative transition probabilities (Arad), branching ratios (β) and radiative lifetimes (τR) for certain excited states of Ho3+ ion are calculated by using intensity parameters. The NIR and visible emission spectra were used to estimate the stimulated emission cross-sections for 5I7→5I8,5F4(5S2)→5I5, 5I6→5I8, 5F4(5S2)→5I6, 5F5→5I8 and 5F4(5S2)→5I8 transitions. Decay curve analysis was reported for 5I6, 5F4(5S2) and 5F5 levels of Ho3+ ions. Gain coefficient was calculated for 5I6→5I8 and 5I7→5I8 transitions which arise at 1.2μm and 2.0μm, respectively. The analysis of present studied glasses suggests that 1.0mol% Ho3+ doped TBZLN glass exhibits relatively better lasing properties than other reported glasses and is favorable for photonic applications.

Lanthanide Doped Dual-Mode Nanophosphor as a Spectral Converter for Promising Next Generation Solar Cells

Herein, we have successfully synthesized a lanthanide based dual-mode nanophosphor (Y0.975Yb0.020 Ho0.005VO4), capable to emit both by down-shifting and upconversion processes, via facile combustion method. The dual-mode emission in phosphor materials is still an unexplored area. The present work covers the study of structure, surface morphology, luminescent behavior and decay profile of the synthesized nanophosphor. The nanophosphor exhibits strong green emission (corresponding to F-5(4), S-5(2) -> I-5(8) transition of Ho3+ ion) on UV excitation (lambda(ex) = 318 nm), via an excited state energy transfer from the charge transfer band of [VO4](3-) to F-5(4) state of Ho3+ ions. On the other hand, an efficient red emission of Ho3+ (F-5(5) -> I-5(8)) is obtained upon infrared excitation (lambda(ex) = 976 nm). We propose that the dual-mode nanophosphor could be an exceptional prospect to incorporate in next generation solar cell applications.

Spectroscopic Properties and Upconversion Studies in Ho3+/Yb3+ Co‐doped Calcium Scandate with Spectrally Pure Green emission

The optical properties of a Ho(3+) /Yb(3+) co-doped CaSc2 O4 oxide material are investigated in detail. The spectral properties are described as a function of doping concentrations. The efficient Yb(3+) →Ho(3+) energy transfer is observed. The transfer efficiency approaches 50 % before concentration quenching. The concentration-optimized sample exhibits a strong green emission accompanied with a weak red emission, showing perfect green monochromaticity. The results of the spectral distribution, power dependence, and lifetime measurements are presented. The green, red, and near-infrared (NIR) emissions around 545, 660, and 759 nm are assigned to the (5) F4 +(5) S2 →(5) I8 , (5) F5 →(5) I8 , and (5) F4 +(5) S2 →(5) I7 transitions of Ho(3+) , respectively. The detailed study reveals the upconversion luminescence mechanism involved in a novel Ho(3+) /Yb(3+) co-doped CaSc2 O4 oxide material.

Influence of modifier oxide on Spectroscopic properties of Ho3+: V4+ co-doped Na2O–SiO2–ZrO2 glasses

• EDS technique has indicated that the glasses have amorphous nature. • From the structural studies depolymerization of network takes place with V 2 O 5 . • The ESR spectra confirm that majority of vanadyl ions are in V 4+ oxidation state. • From the optical investigations, 5 S 2 → 5 I 8 is laser transition. Na 2 O–SiO 2 –ZrO 2 glasses co-doped with variable concentrations of Ho 3+ : V 4+ have been synthesized, characterized by different techniques and finally their luminescence characteristics were investigated. The EDS spectra of the glass samples indicate all the elements are intact in the final composition of prepared glass. The infrared and Raman spectral studies are carried out and the existence of conventional structural units are analyzed. The ESR and optical absorption spectra indicated that a considerable proportion of vanadium ions do exist in V 4+ state in addition to V 5+ state. The absorption and emission spectra of Ho 3+ ions were characterized using J–O theory. The radiative transition probabilities and branching ratio were evaluated from luminescence spectra. The analysis these results indicated the highest values of radiative probabilities and branching ratios for the green emission transition viz., 5 S 2 → 5 I 8 transition among various other transitions of Ho 3+ ions. However, the presence of higher concentration of V 2 O 5 in the glass matrix seems to be a hindrance for getting the high luminescence efficiency especially in the red region.

Concentration Enhanced Upconversion Luminescence in ZrO2:Ho3+, Yb3+ Nanophosphors

The upconversion luminescence properties of ZrO2:Ho3+ and co-doped ZrO2:Ho3+, Yb3+ nanophosphors with various concentrations of Yb3+ ions were synthesized via a solvothermal reaction method. Our samples have a nearby spherical shape and an average crystal size was about 80 nm. For low concentrations of Yb3+ ion, the crystalline structure changed from tetragonal to monoclinic phase as the Yb3+ concentration increased to 3 mol% Yb3+ ions. As the Yb3+ concentration increased to above 5 mol%, ZrO2 nanophosphors displayed a very stable tetragonal phase. The sample shows a strong green (550 nm) and weak red (660 nm) and near infrared (757 nm) upconversion emission corresponding to the transitions of Ho3+:5F4/5S2 --> 5I8, 5F5 --> 5I8 and 5S2 --> 5I7, respectively. The energy transfer (ET) processes between the Ho3+ and Yb3+ ions and the involved mechanisms have been investigated. Experimental results suggest that two-photon upconversion processes are taking place under excitation by a 975 nm.

White upconverted luminescence of Ho3+/Yb3+/Tm3+ tri-doped Gd2Mo3O9 phosphors

Abstract Yb 3+ /Tm 3+ /Ho 3+ tri-doped Gd 2 Mo 3 O 9 phosphors were synthesized by the high-temperature solid-state method. Under 980 nm near-infrared excitation, the white-light emission can be observed, which is consists of the blue, green, and red UC emissions. The green and red emission at 547 nm and 660 nm originated from the transition of Ho 3+ ( 5 S 2 , 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 ) and the blue emission at 475 nm attributed to the transition of Tm 3+ ( 5 G 4 → 5 H 6 ). In this experiment, we selected the optimum concentration ratio of the three rare earths for the bright white emission. The Commission internationale de L’Eclairage (CIE) coordinates for the samples were calculated, and chromaticity coordinates were very close to white light regions. We find that the calculated CIE color coordinates of the Yb 3+ /Tm 3+ /Ho 3+ tri-doped Gd 2 Mo 3 O 9 phosphors changed with the incident pump power from 400 mW/cm 2 to 1000 mW/cm 2 . The upconversion luminescence mechanism of the samples was discussed on its spectral. The white light may be proved to be a candidate material for applications in various fields.

In-band pumped Ho^3+:KY_3F_10 2 μm laser

We report the first observation to our knowledge of room-temperature continuous-wave laser operation on the (5)I(7)→(5)I(8) transition of Ho(3+) ions in a KY(3)F(10) single crystal. Using a Tm-doped silica fiber laser operating at 1938 nm as a pump source, a maximum laser power of 1.8 W was obtained at a wavelength of ~2040 nm for 27 W of absorbed pump power with a slope efficiency of 19.1% with respect to absorbed power. At low cavity output coupling, the lasing wavelength shifted to 2060.5 nm. The beam propagation factor (M(2)) was measured to be <1.06 at the maximum output power, confirming fundamental transverse-mode (TEM(00)) operation. Performing a Caird analysis, we determined resonator round-trip losses and intrinsic slope efficiency of 30% and 43.8%, respectively.

Short-wavelength upconversion emissions in Ho^3+/Yb^3+ codoped glass ceramic and the optical thermometry behavior

Ho(3+)/Yb(3+) codoped glass ceramic was prepared by melt-quenching and subsequent thermal treatment. Under a 980 nm diode laser excitation, upconversion emissions from Ho(3+) ions centered at 540, 650, and 750 nm were greatly enhanced compared with those in the precursor glass. Especially, the short-wavelength upconversion emissions centered at 360, 385, 418, 445, and 485 nm were successfully obtained in the glass ceramic. An explanation for this phenomenon is given based on the fluorescence decay curve measurements. In addition, an optical temperature sensor based on the blue upconversion emissions from (5)F(2,3)/(3)K(8)→(5)I(8) and (5)F(1)/(5)G(6)→(5)I(8) transitions in Ho(3+)/Yb(3+) codoped glass ceramic has been developed. It was found that by using fluorescence intensity ratio technique, appreciable sensitivity for temperature measurement can be achieved by using the Ho(3+)/Yb(3+) codoped glass ceramic. This result makes the Ho(3+)/Yb(3+) codoped glass ceramic be a promising candidate for sensitive optical temperature sensor with high resolution and good accuracy.

Excited state dynamics in Ho:KPb2Cl5

Optical absorption spectra, emission spectra, and fluorescence lifetimes were measured for a number of visible and infrared transitions in Ho3+ doped KPb2Cl5. Judd–Ofelt parameters were obtained by using the conventional approach, as well as by a modified approach that minimizes the fractional difference, rather than the absolute difference, between calculated and measured oscillator strengths. Both procedures gave good overall agreement between measured and calculated lifetimes, with an average difference of ≈15%. This confirms the expectation from the multiphonon energy gap law that most observed transitions in Ho3+:KPb2Cl5 are highly radiative. Emission cross section spectra for the transitions 5F3→5I8, 5G5→5I7, 5F3→5I7, 5F4/5S2→5I7, and 5I7 →5I8 were obtained from measured emission spectra, with the peak cross section values scaled by the Judd–Ofelt calculated oscillator strengths.

2.1μm Emission Spectral Properties of Tm and Ho Doped Transparent YAG Ceramic

Highly transparent Tm:Ho:YAG transparent ceramics were prepared using advanced ceramic technology and their spectroscopic properties were studied for infrared laser applications. Following the Judd-Ofelt procedure several spectroscopic properties such as the radiative transition probability (Arad), radiative decay time (� rad) and fluorescence branching ratio (� ) are quantitatively obtained from the absorption spectrum. The absorption and emission cross sections corresponding to the 5I7 → 5 I8 transition of Ho 3+ at 2.1 � m have been evaluated following Mc Cumber theory and found that the obtained emission spectrum very well correlates to the simulated emission spectral data. The optical gain spectrum spread from 1800 nm to 2150 nm with a spectral width of over 107 nm and maximum gain coefficient of 0.44 cm −1 . Thus it is expected that the Tm 3+ :Ho 3+ :YAG ceramics

Composition-dependent optical transitions and 2.0 μm emission properties of Ho 3+ in xGeO 2-(80– x)TeO 2-9.5ZnF 2-10NaF-0.5Ho 2O 3 glasses

Ho 3+ doped glasses with various compositions xGeO 2-(80- x)TeO 2-9.5ZnF 2-10NaF-0.5Ho 2O 3 ( x=0, 10, 20, 30, 40, 50, 60, 70 and 80) were prepared by a melt-quenching technique. The composition-dependent optical transition properties of Ho 3+ were investigated in the framework of Judd-Ofelt theory. The emission cross sections for 5I 7→ 5I 8 transition of Ho 3+ in these glasses were calculated according to McCumber theory, and their compositional dependence was discussed. A simple method was proposed in calculating the emission cross sections of 5I 7→ 5I 8 transition, and the calculation results were compared with those derived from McCumber theory. Finally, the optical gain coefficient spectra for 5I 7→ 5I 8 transition were also analyzed.

Efficient first-order resonant near-infrared quantum cutting in β-NaYF 4:Ho 3+,Yb 3+

We demonstrated an efficient two-photon near-infrared (NIR) quantum cutting (QC) in Ho 3+–Yb 3+ co-doped hexagonal β-NaYF 4, which could efficiently convert an incident high-energy photon in the wavelength region of 300–550 nm into two NIR photons. Underlying mechanism for the two-photon NIR-QC process is analyzed in terms of static and dynamic photoemission and monitored excitation spectra. It is found that NIR-QC can occur through two possible energy transfer (ET) approaches: (i) the excited Ho 3+: 5F 3 state may simultaneously excite two Yb 3+ neighbors via a cooperative ET process, and (ii) the NIR-QC can be feasibly induced by a first Ho 3+( 5S 2, 5F 4) + Yb 3+( 2F 7/2) → Ho 3+( 5I 6) + Yb 3+( 2F 5/2) resonant ET process and a sequential 5I 6 → 5I 8 transition of Ho 3+. This novel NaYF 4:Ho 3+,Yb 3+ NIR-QC phosphor, may explore a new approach to maximize the performance of solar cells.

Towards efficient upconversion and downconversion of NaYF 4:Ho 3+,Yb 3+ phosphors

NaYF 4 microcrystals co-doped with Ho 3+ and Yb 3+ were prepared by a facile hydrothermal synthesis. The products were characterized by X-ray diffractometer, scanning electron microscopy, and photoluminescence spectroscopy. Upon excitation with a 980 nm laser diode, the sample shows an intense green upconversion emission centered at 540 nm corresponding to the 5S 2→ 5I 8 transition of Ho 3+. The quadratic dependence of the green emission intensity on the excitation power reveals a two-phonon upconversion process. On the contrary, upon excitation with 448 nm, both visible and near-infrared emissions peaked at 483, 540, 644, 749, and 978 nm are simultaneously observed, which could be assigned to the electronic transitions of Ho 3+: 5F 3→ 5I 8, 5S 2→ 5I 8, 5F 5→ 5I 8, 5S 2→ 5I 7, and Yb 3+: 2F 5/2→ 2F 7/2, respectively. The energy transfer processes between Ho 3+ and Yb 3+ ions and the involved mechanisms have been investigated and discussed.

Upconversion luminescence of Yb 3+/Ho 3+/Er 3+/Tm 3+ co-doped KGd(WO 4) 2 powders

Different lanthanide ions (Yb 3+/Ho 3+/Er 3+/Tm 3+) codoped KGd(WO 4) 2 phosphors were prepared by high-temperature solid-state reaction. The upconversion luminescence properties of two-ion and three-ion co-doped KGd(WO 4) 2 phosphors were investigated in detail. The concentration quenching effect of the two-ion co-doped KGd(WO 4) 2 phosphors was studied, and the optimum concentration of Ho 3+, Er 3+ and Tm 3+ are 2 mol.%, 2 mol.% and 3 mol.%, respectively. The Yb 3+/Ho 3+/Tm 3+ co-doped KGd(WO 4) 2 sample is the best white upconversion luminescence material among three-ion co-doped KGd(WO 4) 2 phosphors. The CIE coordinates for the samples were calculated, and chromaticity coordinates were close to white light regions. The upconversion luminescence mechanism of the samples was discussed. The upconversion luminescence of Ho 3+ and Er 3+ was both produced through two-photon process. The emissions of Ho 3+ at 546 and 654 nm originated from the transition of Ho 3+ ( 5S 2→ 5I 8 and 5F 5→ 5I 8), while those of Er 3+ at 530 and 551 nm were attributed to the transition of Er 3+ ( 2I 11/2→ 4I 15/2 and 4S 3/2→ 4I 15/2). The upconversion luminescence mechanism of Tm 3+ was a three-photon process. The blue emission of Tm 3+ was due to the transition of Tm 3+ ( 1G 4→ 3H 6).

Upconverted photoluminescence in Ho3+ and Yb3+ codoped Gd2O3 nanocrystals with and without Li+ ions

The upconversion photoluminescence of Ho(3+) ion sensitized by Yb(3+) ion in Ho(3+)/Yb(3+) codoped Gd(2)O(3) nanocrystals with and without Li(+) is investigated in this paper. Strong fluorescence in the green (534-570 nm) and red (635-674 nm) regions of the spectrum has been observed, arising from the (5)F(4)/(5)S(2) → (5)I(8) and (5)F(5) → (5)I(8) transitions of Ho(3+) ion, respectively. Yb(3+) ion is considered to be a better sensitizer for catching enough pumping energy and transferring considerable energy to Ho(3+) in the Ho(3+)/Yb(3+) system. The upconversion intensity emitted by Ho(3+) is greatly enhanced when Li(+) is added to the Ho(3+)/Yb(3+) codoped Gd(2)O(3) nanocrystals.

2.0 μm Emission properties of transparent oxyfluoride glass ceramics doped with Yb 3+–Ho 3+ ions

Transparent oxyfluoride glass and glass ceramics doped with 3.0 mol% Yb 3+ and 0.5 mol% Ho 3+ ions have been prepared. The investigated samples show efficient 2.0 μm emission. The absorption and emission cross sections corresponding to the 5I 7– 5I 8 transitions of Ho 3+ (at 2.0 μm) have been calculated according to the McCumber theory. Glass sample heat-treated at 470 °C has the maximum absorption and emission cross sections of 5.58 × 10 −21 cm 2 at 1949 nm and 6.64 × 10 −21 cm 2 at 2034 nm. The Yb 3+–Ho 3+ doped oxyfluoride glass ceramic exhibits an advantage for application in 2.0 μm laser devices.

ChemInform Abstract: Investigation of LiXO3 (X: Nb, Ta) Crystals Doped with Luminescent Ions. Recent Results

Abstract Processes of transfer of excitation from levels populated by diode laser pumping to upper laser levels in LiTaO 3 :Tm and LiTaO 3 :Ho are considered. Stimulated emission cross section for the 3 F 4 – 4 H 6 transition of Tm and for the 5 I 7 – 5 I 8 transition of Ho in lithium tantalate have been evaluated. Preliminary data concerning the contribution of radiative transitions and multiphonon relaxation to the decay of excited states of Er, Tm and Ho in LiNbO 3 and LiTaO 3 are compared.

Upconversion luminescence of Ho 3+ sensitized by Yb 3+ in transparent glass ceramic embedding BaYF 5 nanocrystals

Transparent SiO 2–Al 2O 3–BaCO 3–YF 3–BaF 2 glass ceramics co-doped with Yb 3+/Ho 3+ ions were prepared by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscopy observation revealed that BaYF 5 nanocrystals incorporated with Yb 3+ and Ho 3+ were precipitated homogeneously among the oxide glass matrix. Three upconversion emission bands centered at 483 nm, 545 nm and 645 nm, corresponding to the 5 F 3 → 5 I 8, 5 S 2, 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho 3+ respectively, were detected under 976 nm excitation, ascribing to the efficient energy transfer from Yb 3+ to Ho 3+. The red emission is prevailing in the precursor glass, while the green one turns to be dominant in the glass ceramic.