Comparative impact of Nd3+ ion doping concentration on near-infrared laser emission in lead borate glassy materials

Comparative impact of Nd3+ ion doping concentration on near-infrared laser emission in lead borate glassy materials

Journal Pre-proof Comparative impact of Nd3+ ion doping concentration on near-infrared laser emission in lead borate glassy materials K. Venkata Rao, ...

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Journal Pre-proof Comparative impact of Nd3+ ion doping concentration on near-infrared laser emission in lead borate glassy materials K. Venkata Rao, S. Babu, C. Balanarayana, Y.C. Ratnakaram

PII:

S0030-4026(19)31460-3

DOI:

https://doi.org/10.1016/j.ijleo.2019.163562

Reference:

IJLEO 163562

To appear in:

Optik

Received Date:

10 July 2019

Accepted Date:

7 October 2019

Please cite this article as: Rao KV, Babu S, Balanarayana C, Ratnakaram YC, Comparative impact of Nd3+ ion doping concentration on near-infrared laser emission in lead borate glassy materials, Optik (2019), doi: https://doi.org/10.1016/j.ijleo.2019.163562

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Comparative impact of Nd3+ ion doping concentration on near-infrared laser emission in lead borate glassy materials K. Venkata Rao1*, S. Babu2,3 , C. Balanarayana4, Y.C. Ratnakaram5 1

Department of Physics, S.B.V.R. Degree College, Badvel, Kadapa, Andhra Pradesh-516227, INDIA. FunGlass - Centre for Functional and Surface Functionalized Glass, Alexander Dubček University of Trenčín, 911 50 Trenčín, Slovakia 3 Institute of Ceramics and Glass, Spanish National Research Council- CSIC, C / Kelsen 5, Campus of Cantoblanco. 28049 Madrid, Spain 4 Department of Physics, Loyola Degree College, Pulivendula, Kadapa, Andhra Pradesh-516390, India 5 Department of Physics, Sri Venkateswara University, Tirupati-517502, India 2

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Corresponding author Email address: [email protected] (Tel.: +919441744263)

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Highlights

Nd3+ doped lead borate glasses were prepared by melt quenching technique.



Nd3+ doped LB glasses exhibited intense NIR emission at 1.06 μm (4F3/2→4I11/2).



Optimized neodymium concentration is found to be 0.8 mol% in this lead borate glasses.



Absorption, emission and decay profiles were studied and useful for developing



NIR laser materials.

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Abstract

Different concentrations (0.2-1.0 mol%) of Nd3+ doped lead borate glass (LB) systems were

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prepared by melt quenching technique and have been studied using XRD and optical studies. Based on the calculations of Judd-Ofelt (J-O) theory derived from the optical absorption spectra, three J-O parameters have been obtained. Various radiative parameters (such as radiative transition probability (Arad), branching ratio (βcal), absorption cross-sections (Σ), radiative lifetime (τR) and etc., have been predicted through J-O parameters. Luminescence spectra were measured

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for all the samples. It has been observed that luminesce intensity gradually increased up to 0.8 mol % of Nd3+ and further increase in concentrations causes that the luminescence spectral intensity falls. This is proposed due to the concentration quenching of neodymium ions in the LB glass system. LB glass system with 0.8 mol % is found to be most intensive one in emission at 1.06 μm related to 4F3/24I11/2 in near infrared (NIR) transition.

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Key words: Absorption; Photoluminescence.

Judd-Ofelt,

Lead

borate

glasses;

emission

cross-section;

1. Introduction Owing to enlarge in global demand for solid state and other energy efficient lighting systems, there is great impact on photonic field.

Along with that, the growth of lanthanide (Ln)

spectroscopy is fast and significant. In solids, glasses are the most promising host materials for

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photonics due to their peculiar properties like low absorption, high stability and fast response.

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Optical absorption and luminescence studies of Ln-doped glasses found extensive applications in various fields such as window layers for solar cells, energy sensors [1], laser gain medias, etc.

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Ln-doped luminescent materials are known to emit at distinct and different wavelengths depending up on energy level mechanisms.

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Particularly the present research focused on the Nd3+: 4F3/24I11/2 lasing emission transition

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at 1.06 µm which is prominent one and also it gives two less intensity peaks at 0.8 µm (4F3/24I9/2 ) and 1.3 µm (4F3/24I13/2) [2]. Even though there are variety of hosts in glasses such as silicate,

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phosphate and telluride, borate host offers several prominent properties such as easier of making at low temperature, high chemical stability, more doping concentration accessibility and low cost [3]. Particularly, fluoride based borate glass system for rare earth doping is useful due to low phonon energy which reduces non-radiative emission transition and contributes to enhance

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luminescence spectral intensity and also accessing of wide spectral window. It is necessary to improve better glass composition with reference to concentration of rare earth ion for better optical properties. The luminescence properties are mainly depends on the host glass composition and concentration of rare earth ion. Borate based glasses which are containing fluorine have attracted 2

much attention due to their good chemical and thermal stabilities comparably with silicate and phosphate glasses [4]. The borate glass environment possess advantageous photonic properties like good transparency, high density, optimum band widths, good infrared transmission, high mechanical stability, corrosion resistance and low cost. Fluoride glasses have been regarded as attractive materials for photonic applications, such as optical amplifiers, short pulse laser

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oscillators and mid-infrared lasers [5]. The Judd-Ofelt (J-O) theory has been applied to interpret the local environmental of Nd3+ in terms of crystal field symmetry and bond covalncy, studying

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changes of the experimentally fitted J-O parameters.

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Recently, Ali et al. [6], studied optical properties of Nd3+ doped in TeBiY Borate system. Hala A. Soliman et al. [7], investigated thermo-luminescence properties in alkali borate glass

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through Nd3+ doping. Barbara Klimesz et al. [8], prepared oxyfluorotellurite glasses and examined spectroscopic properties as well as energy transfer process of Nd 3+ ion. Vijayalakshmi

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et al. [9], studied structural, dielectric and photoluminescence properties of Nd 3+ doped lithium-

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fluoro-zinc-borate glasses for solid state laser applications.

The purpose of this work is to evaluate the effect of concentration on the optical properties of Nd3+ doped lead borate glass system. X-ray diffraction (XRD) measurements were used to identify the amorphous phase present in the glass and samples were then exposed to emission

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characteristics. The Judd–Ofelt intensity parameters were calculated and used to analyze spectroscopic properties such as radiative transition probabilities (AR), absorption cross-sections (Σ), branching ratios (βR) and radiative lifetimes (τR). From the emission spectra stimulated emission cross-sections (σp) have been calculated for certain transitions. Experimental lifetimes of 4F3/2 of Nd3+ were obtained from decay profiles. 3

2. Experimental In the present work, different concentrations of Nd3+ doped LB glasses with the chemical compositions given below were prepared. 0.2NdLB: 49.8B2O3+20PbO+15MgF2+15NaCl+0.2Nd2O3 0.4NdLB: 49.6B2O3+20PbO+15MgF2+15NaCl+0.4Nd2O3

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0.6NdLB: 49.4B2O3+20PbO+15MgF2+15NaCl+0.6Nd2O3 0.8NdLB: 49.2B2O3+20PbO+15MgF2+15NaCl+0.8Nd2O3

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1.0NdLB: 49.0B2O3+20PbO+15MgF2+15NaCl+1.0Nd2O3

These glasses were prepared using the chemicals such as boric acid, lead oxide, magnesium

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fluoride, sodium chloride and neodymium oxide by melt quenching method. All these chemicals are of analar grade with 99.9% purity. The raw materials were thoroughly mixed in an agate

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mortar and melted in an electronic furnace in the temperature range 900-1100oC for 1h. Then, the mixture was quenched by pouring it on a preheated brass plate. The prepared glass samples were

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introduced into oven (@ 250oC) in order to remove thermal strain and then polished to do spectral measurements.

The X-ray diffraction (XRD) patteren was recorded using SIEFERT diffracto meter employing Co Kα radiation as an excitation source. were

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measurements

recorded

using

Perkin-Elmer

The optical absorption spectrum Lambda

950

spectrometer.

The

photoluminescence spectra and decay curves of neodymium ion were recorded using TRIX 550 monochromator with liquid nitrogen cooled for detector. All these measurements were carried out at room temperature.

3. Results and discussion 4

3.1 XRD spectrum The X-ray diffraction patterns (XRD) of different concentrations of Nd3+ were recorded and 0.8 mol% of Nd3+ doped LB glass is shown in Fig. 1. The XRD pattern does not contain any diffracting lines, suggesting the existence of long range structural disorder in the glass under investigation. This confirms the amorphous nature of the prepared glass.

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3.2 Ultra violet- visible- near infrared absorption Absorption spectrum of 0.8 mol% of Nd3+ doped LB glass sample in the wavelength region

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of 450–920 nm is displayed in Fig. 2. From the figure, eight absorption bands are clearly observed

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which are assigned to various excited states with 4I9/2 as the ground state Nd3+ ion in LB glasses. The positions of these absorption transitions of are at 471, 526, 583, 621, 681, 746, 801 and 873

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nm originates from the 4I9/2 ground state to the various excited states of Nd3+ ion. The absorption band of Nd3+ located at ~583 nm corresponds to the hypersensitive transition which is dominated

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in intensity than other transitions of Nd3+ ions. Overlapped absorption transitions (4I9/2 → D3/2+2G9/2+2K13/2 and 4I9/2 →4F5/2+ 2H9/2) have been noticed in the spectrum due to the presence

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of closed energy levels in Nd3+ ions and these difficulties can be resolved by addition of both the dipole strengths and the squared reduced matrix elements of overlapping transitions [10, 11]. The Judd-Oflet (J-O) [12, 13] parameters (, =2,4 and 6 ) are obtained with help of absorption spectrum. The root mean square (RMS) deviation value of 0.76 is obtained between

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calculated spectral intensities (fexp) and experimental spectral intensities (fcal), indicating the good fit between two magnitudes and also good consistency of J-O calculation route. These results are shown in Table 1. It is observed that the order of  parameters is  2>4>6 for the 0.8NdLB glass matrix. The higher value of  2 parameter and lower values of  4 and  6 parameters are

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related to covalency and rigidity nature of glasses respectively. The obtained value of Ω2 for 0.8 mol% of Nd3+ doped LB glass is 5.37x10-20 cm2

3.3 Radiative properties Using the J-O intensity parameters (Ωλ), radiative transition probabilities (Arad), branching

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ratios (βcal), absorption cross-sections (Σ) and radiative lifetimes (τR) for certain excited states of 0.8 mol% of Nd3+ doped LB glass matrix are calculated [14]. Radiative lifetimes (τR) for the

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excited states 4G9/2, 4G7/2, 4G5/2, 2H11/2, 4 F9/2, 4 F5/2 and 4F3/2 of 0.8 mol % Nd3+ ion doped LB glass are estimated. The radiative lifetimes for the above excited levels are 65, 90, 43, 2094, 236, 214

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and 297 μs respectively. The order of magnitude of radiative lifetimes is 2H11/2>4F3/2>4F9/2>4F5/2

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>4G7/2 >4G9/2 >4G5/2 in this glass matrix [15]. Radiative lifetime is higher for the 2H11/2 state and lower for the 4G5/2 excited level. It is observed that, among the seven transitions, 4G9/2 →4I11/2

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transition shows higher absorption cross-sections and 4G7/2 →4I11/2 transition shows higher branching ratios (β) for the titled glass matrices, hence it is suggested that this transition can be

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usefull for laser transition. 3.4 Luminescence properties

Fig. 3, shows the luminescence emission spectra of Nd3+ doped LB glass matrix for 0.2NdLB, 0.4NdLB, 0.6NdLB, 0.8NdLb and 1.0NdLB glasses in 825–1500 nm. Three emission

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peaks are observed at nearly 894, 1059 and 1333 nm corresponding to 4F3/2→4I9/2, 4I11/2 and 4I13/2 transitions, respectively [16]. From the emission spectra, it is observed that emission intensities increase up to 0.8 mol% of neodymium and then decreases. By adjusting the doping concentration in glass system, the quenching was observed in emission intensity. It is occurring due to the

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increasing of non-radiative (NR) energy transfer through cross relaxation and resonant energy channels among Nd3+ ions. It can be observed that during increasing concentration from 0.2 mol% to 0.8 mol% of neodymium, the emission intensity is enhanced in three fold times and then decreases. The main reason of such decrement is due to the concentration quenching. The concentration clusters can

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be a principal for the differences in the behavior of the luminous. Due to the ion-ion interaction of Nd3+ ions, some transferring processes occurred in LB glass matrix. From Fig.4, it is observed

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that, the near infrared transition located at 1.06 μm has high emission intensity. From the emission spectra, lasing transition can be assessed from the magnitudes of effective line widths (λeff),

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branching ratio (βexp), and peak stimulated emission cross-sections (σP). From Table 2 it can be

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observed that the values of σP, βexp and λeff are more for the 4F3/2→4I11/2 transition as compared to other two, 4F3/2→4I9/2 and 4F3/2→4I13/2 transitions. It can be concluded that 4F3/2→4I11/2 transition

[17].

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3.5 Decay curve analysis

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is more effective in 0.8NdLB glass, hence the transition can be used for the NIR laser applications

With 808 nm excitation, into the 4I9/2→ 4F5/2+2H9/2 absorption (excitation) band and the 4

I13/2→4F9/2 transition is more favourable way to depopulate nonradiatively through the

multiphonon relaxation (MPR) due to the fact that the energy gap between them is low. No

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emissions from other energy levels are expected. The MPR from the 4F9/2 level is negligible owing to fact that the next level (6F1/2) lies lower by about ~6900 cm-1. This wide energy gap between the 4F9/2↔6F1/2 levels leads to a high quantum efficiency of the 4F9/2 emitting level [18] and emission takes place from this level as shown in Fig. 4.

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The decay profiles of 4F3/2 level of Nd3+ doped LB glasses with the variation of Nd3+ content while maintaining with a fixed emission at 1.06 μm, (4F3/2→4I11/2) and excitation at 808 nm are shown in Fig. 5. In case of bi-exponential function [19] t

1

)  A 2 exp(

and τexp obtained as

2

)

A1 12  A2 22 A1 1  A2 2

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 exp 

t

of

I( t )  A1 exp(

-p

where A1, A2 and τ1, τ2 are fitting parameters

It is observed that the decay lifetimes decrease with increasing neodymium content in the

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LB glass system. The lifetimes were found to be 910, 895, 800, 745, 693 and 580 μs for the 0.2NdLB, 0.4NdLB, 0.6NdLB, 0.8NdLB and 1.0NdLB glasses respectively. The decay lifetimes

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decrease from 910 μs to 580 μs with increasing concentration. The lifetime value drops to 580 μs when Nd3+ content increases to 1.0 mol% which might be due to the larger amount of activator

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ions in the glass system. For 0.8NdLB and 1.0NdLB glasses, the decay profiles are fitted to nonexponential function at short times. This type of activity is due to energy transfer (ET) between two Nd3+ atoms and concentration quenching. In order to investigate the process involved in the ET mechanism, the non-exponential decay curves for the 4F9/2 level of Nd3+ ions have been

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analyzed using Inokuti–Hirayama (I-H) model [20]. I(t)=IOexp{-t/τO-Q(t/τO)3/S} In present system, the variable parameter is S for the decays were fitted S=6.

From this model it is assessed that ET occurs through dipole–dipole (d-d) interaction. 4. Conclusions 8

In the present study, neodymium doped LB glasses were prepared by melt quenching method, and their luminescence has been investigated. Structural properties were accomplished from XRD (X-Ray Diffractometer). It is observed that order of  parameters is 2> 4>6 for the 0.8NdLB glass. Higher  2 parameter and lower 4 and 6 parameter values represented that the present glasses have more covalency and rigidity. J-O intensity parameters are used further to

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evaluate the different radiative properties like AR, τR and β of certain excited states. The F3/2→4I11/2 transition has higher AR and βcal values. These values suggested that the present

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0.8NdLB glass have intensive 4F3/2→4I11/2 transition compared to other two transitions. By

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adjusting the doping concentration in glass system, the quenching was observed in emission intensity which is due to the concentration quenching. The photoluminescence spectra exhibit

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three prominent transitions out of which, the near infrared transition located at 1.06 μm has higher emission intensity. 0.8NdLB sample shows higher branching ratios, transition probabilities, and

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emission cross-sections for 4F3/2→4I11/2 transition. These values suggested that the present glasses are more suitable for NIR applications at 1.06 μm. Photoluminescence decay lifetimes are

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determined by fitting the decay data with the mono exponential decay equation up to 0.6 mol% of neodymium. The decay lifetimes decrease with increasing of Nd3+ concentration due to the concentration quenching and energy transfer. The IH model was evaluated the energy transfer

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between Nd3+ -ions are dipole–dipole. This approach shows the present prepared LB glass is useful towards the development of near infrared lasing materials. References

[1] F. Lahoz n , C. Pe´rez-Rodriguez, S.E. Hernandez, I.R. Martı´n, V. Lavin, U.R. RodriguezMendoza, Sol. Energy Mater Sol. Cells 95 (2011) 1671–1677. 9

[2] Krennrich, D., Knappe, R., Henrich, B. et al. Appl. Phys. B (2008) 92: 165. https://doi.org/10.1007/s00340-008-3069-4. [3] K.Vijaya Kumar, A.Suresh Kumar, Opt. Mater. 35, (2012) 12-17. [4] M.Jayasimhadri, L.Rama Moorthy, R.V.S.S.N.Ravikumar, Opt. Mater. 29 (2007) 13211326.

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[5] YingTian, JunjieZhang, Xufeng Jing, ShiqingXu, Spectrochim. Acta A 98 (2012) 355-358. [6] A. Ali1, M. H. Shaaban, Silicon (2018) 10:1503–1511.

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[7] Hala A. Soliman, Elsayed Salama, Int. J. Appl. Glass Sci. 2018;9:435–443.

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[8] Barbara Klimesza, Radosław Lisieckib, Witold Ryba-Romanowski, J.Lumin. 199 (2018) 310–318

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[9] L. Vijayalakshmi, K. Naveen Kumar, G. Bhaskar Kumar, Pyung Hwanga J. Non-Cryst. Solids 475 (2017) 28–37

480, (2009) 208-215.

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[10] G.N.Hemantha Kumar, J.L.Rao, K.Ravindra Prasad, Y.C.Ratnakaram J Alloys Compd.

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[11] D.Rajesh, Y.C.Ratnakaram, M.Seshadri, A.Balakrishna, T.Satya Krishna, J. Lumin. 132, (2012) 841-849.

[12] B.R. Judd, Phys. Rev. 127 (1962) 750–761. [13] G.S. Ofelt, J. Chem. Phys. 37 (1962) 511–520.

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[14] K.Venkata Rao, S.Babu, G.Venkataiah, Y.C.Ratnakaram, J. Mol. Struct. 1094, (2015) 274-280.

[15] V. Reddy Prasad

M. Seshadri

S. Babu

Y. C. Ratnakaram, (2016) 1-9,

https://doi.org/10.1002/bio.3200. [16] K.Brahmachary, D.Rajesh, S.Babu, Y.C.Ratnakaram, J. Mol. Struct 1064 (2014) 6-14. 10

[17] Y.C.Ratnakaram, S.Babu, L. Krishna Bharat, C.Nayak, J. Lumin. 175 (2016) 57-66. [18] I.Pal, A.Agarwal, S.Sanghi, M.P.Aggarwal, Opt. Mater. 34 (2012) 1171-1180. [19] T. Sasikala, L. RamaMoorthy, A. MohanBabu, T. SrinivasaRao, J. Solid State Chem. 203 (2013) 55–59. [20] Sk.Nayab Rasool, L.Rama Moorthy, C.K.Jayasankar, Optics Commun. 311 (2013) 156-

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162.

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Figure captions

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1. XRD profile for lead borate host glass matrix 2. Absorption spectrum of 0.8 mol% Nd3+ doped lead borate glass matrix 3. Emission spectra of Nd3+ doped lead borate glass matrix with different concentrations 4. Energy level scheme of Nd3+ doped lead borate glass matrix 5. Decay profiles for various concentrations of Nd3+ doped of lead borate glasses

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12

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re

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-p

re

lP

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13

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-p

re

lP

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15

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-p

re

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Fig.4

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Fig.5

Table 1 Experimental (fexp) and calculated (fcal) spectral intensities (x10-6) of different absorption bands and Judd-Ofelt intensity parameters (Ωλ, x10-20 cm2) for 08NdLB glass matrix

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S.NO 1

2

Transition

fexp

K13/2+2G9/2+2D3/2

1.91

1.99

G7/2

3.91

4.10

G5/2+2G7/2

21.14

22.12

H11/2

0.16

0.13

4

1.09

1.13

4

2 3 4 5

16

4

2

F9/2

fcal

6

4

S3/2+4F7/2

6.64

6.99

7

4

F5/2+2H9/2

6.56

6.98

1.84

2.10

4

8

F3/2

±0.76

Ω2

5.37

Ω4

4.03

Ω6

3.27

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RMS deviation

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Table 2 Emission band positions (p, nm), radiative transition probabilities (A, s-1), peak stimulated emission cross-sections ( px10-21cm2) and branching ratios (exp, %) of 0.8 mol% of

4

2

4

4

F3/2→4I11/2

F3/2→4I13/2

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3

F3/2→4I9/2

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p AR σp exp

0.8 mol%

893 835 1.21 23

p AR σp (exp

1066 2048 2.01 68

p AR σp βR exp

1336 460 0.79 13 9

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1

Parameter

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Transition

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S. No

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Nd3+ doped LB glass matrix.