Investigation of Green and 1.53 μm emission characteristics of Er3+ doped bismuth phosphate glasses for laser applications

Accepted Manuscript 3+ Investigation of Green and 1.53�μm emission characteristics of Er doped bismuth phosphate glasses for laser applications S. Damodaraiah, V. Reddy Prasad, Y.C. Ratnakaram PII:

S0925-8388(18)30159-2

DOI:

10.1016/j.jallcom.2018.01.158

Reference:

JALCOM 44622

To appear in:

Journal of Alloys and Compounds

Received Date: 2 August 2017 Revised Date:

4 December 2017

Accepted Date: 10 January 2018

Please cite this article as: S. Damodaraiah, V.R. Prasad, Y.C. Ratnakaram, Investigation of Green 3+ and 1.53�μm emission characteristics of Er doped bismuth phosphate glasses for laser applications, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2018.01.158. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical Abstract:

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Investigation of Green and 1.53µm Emission Characteristics of Er3+ Doped Bismuth Phosphate Glasses for Laser Applications S. Damodaraiah, V. Reddy Prasad, Y.C. Ratnakaram* Department of Physics, Sri Venkateswara University, Tirupati 517502, A.P., India

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Abstract

Erbium (Er3+) ion doped bismuth phosphate (BiP) glasses were fabricated by melt quenching technique. In the current project, studied the influence of bismuth content and Er3+ ion doping concentration on photoluminescence (PL) performance and therefore find out the

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most qualified combination of bismuth and Er3+ for developing compact optical fibre lasers and amplifiers operating at 1.53 µm. Optical absorption measurements are carried out and

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analysed through Judd-Ofelt (JO) and Mc-Cumber theories from which JO parameters, absorption and stimulated emission cross-sections are determined. The studied glasses show intense and broad visible emission at 545 nm (green) for 4S3/2→4I15/2 transition with the excitation 379 nm might be useful for green laser applications. The luminescence behaviour of 4I13/2→4I15/2 transition in the wavelength region 1400-1700 nm and its suitability for optical amplifier applications and also for NIR laser have been discussed with parameters such as

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stimulated emission cross-section (σe), gain bandwidth (∆G) and optical gain (G). The decay curves for both 4S3/2 (visible) and 4I13/2 (NIR) levels are discussed and they are exhibiting non-exponential nature for all the studied BiP glasses. Among all the BiP glasses, Er-1.0 glass exhibited higher σe, ∆G and G values suggesting the suitability for optical amplifier and

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NIR laser applications.

Keywords: FTIR spectra;

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P MAS NMR Spectroscopy; Judd-Ofelt theory; Mc-Cumber

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theory; Photoluminescence; Decay profiles. Email address: [email protected]

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ACCEPTED MANUSCRIPT 1. Introduction Over the recent past, tremendous amount of research work has been carried out on the study of luminescent properties of rare earth (RE) ions doped glass materials due to the unique applications in the field of optical communications [1]. Among RE ions, erbium (Er) has found wide variety of applications in third telecommunication window as near-infrared

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(NIR) solid-state lasers and optical amplifiers [2-4]. Erbium doped fiber amplifier (EDFA) is one of the important devices used in the 1.53 µm optical communication window because of its transition 4I13/2→4I15/2. EDFA make it possible to amplify signals in the range of C-band (1530-1565 nm) or S-band (1460-1530 nm) or L-band (1570-1610 nm) [5, 6]. Also, Er3+ ions exhibit dominant emission transition, 4S3/2→4I15/2 at around 18,400cm-1 and are more suitable

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for green emission lasers. When exciting at 980 nm, the Er3+ ions exhibit an optically transparent window in the NIR region (1400–1600 nm) which is advantageous due to low

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auto-fluorescence background, high signal to noise ratio, high detector sensitivity and high penetration depth in biological tissues [7].

The selection of suitable host matrix and chemical composition play a vital role in developing RE doped optical devices and their optical properties can be tailored over a considerable range by the choice of network former and network modifier [1]. Phosphate

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glass hosts possess several advantages over traditional glass formers such as borate and silicate glasses due to their unique properties, such as high thermal expansion coefficients, low viscosity, low melting and softening temperatures, high electrical conductivity, excellent optical characteristics and ion exchangeability etc. [8, 9]. More interestingly, as a host,

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phosphate glass allows high RE ion solubility, i.e. clustering effect does not take place or only at very high RE ion concentrations [9, 10]. However, these glasses have relatively poor

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chemical durability which limits their practical applications but it can be improved by addition of different metal oxides such as Al2O3, TiO2, Bi2O3 etc., as these oxides form relatively stable M–O–P cross-linked bonds [11]. It has been reported that Bi2O3 occupies both network-forming and network-modifying positions in oxide glasses and therefore the Bi2O3 contained glasses are good candidates for practical applications because of its high mechanical strength, thermal stability, chemical durability and ease of fabrication [12-14]. Recently, more works were reported based on Er3+ doped glasses for optical amplifier and NIR laser applications at 1.53 µm. Gomes et al. [15] studied optical and spectroscopic study of erbium doped calcium borotellurite glasses. Babu et al. [14] studied the spectroscopic and laser properties of Er3+ doped fluoro-phosphate glasses as promising candidates for broadband optical fiber lasers and amplifiers. Kesavalu et al. [5] studied 2

ACCEPTED MANUSCRIPT influence of Er3+ ion concentration on optical and photoluminescence properties of Er3+doped gadolinium-calcium silica borate glasses. Annapoorani et al. [7] studied the investigations on structural and luminescence behaviour of Er3+ doped lithium zinc borate glasses for laser and optical amplifier applications. In the present work, 0.5Er3+ doped bismuth modified (0, 5, 10 and 15 mol%) BiP

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glasses were prepared by melt quenching technique and investigated for higher emission intensity glass matrix. Among the bismuth modified glasses, Bi-15 glass showed higher emission intensity. To increase further the luminescence of this glass matrix, the concentration of erbium ion was varied from 0.1 mol% to 2.0 mol% by keeping Bi2O3

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content at 15 mol%. Present study deals with an investigation of structural properties such as XRD, SEM, EDS, FTIR and 31P MAS NMR and optical properties such as energy band gap,

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absorption, emission and decay lifetime measurements of Er3+ doped BiP glasses. A detailed study on visible, NIR emission and decay lifetime properties was carried out. Using McCumber and J-O theory, absorption and emission spectra were analysed. Gain bandwidth and optical gains were evaluated for the transition, 4I13/2→4I15/2 for optical amplifier applications. The results were examined with respect to the composition (Bi2O3) and concentration (Er3+) effects and are compared with the other recently reported glass systems.

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2. Experimental 2.1 Glass preparation

A series of ((79.5–x)P2O5+10Li2O+10Na2O+0.5Er2O3 +xBi2O3 where x=0; 5; 10; and

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15 mol% and (65–y)P2O5+15Bi2O3+10Li2O+10Na2O+yEr2O3 where y= 0.1; 0.5; 1.0; 1.5 and 2.0 mol%) different BiP glass systems were obtained by the conventional melt quenching technique. The chemical reagents of analar grade NH4H2PO4, Bi2O3, Na2CO3, Li2CO3 and

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Er2O3 of high purity (99.9%) reagents were used as starting materials. The reagents were mixed in appropriate amounts and thoroughly ground in an agate mortar to obtain homogeneous mixture. This mixture was heated in porcelain crucible using an electric


furnace at 1100 0C for 1 hour. The melt was quickly cooled by casting it onto a brass mould at room temperature (RT). The obtained glass samples were transparent and circular in shape. Based on bismuth oxide compositions and erbium ion concentrations, the obtained glass samples are classified as follows: 1. Bi–0:

79.5P2O5+10Li2O+10Na2O+0.5Er2O3+0Bi2O3

2. Bi–5:

74.5P2O5+10Li2O+10Na2O+0.5 Er2O3+5Bi2O3 3

ACCEPTED MANUSCRIPT 3. Bi–10: 69.5P2O5+10Li2O+10Na2O+0.5Er2O3+10Bi2O3 4. Bi–15: 64.5P2O5+10Li2O+10Na2O+0.5Er2O3+15Bi2O3 and 5. Er–0.1: 64.9P2O5+15Bi2O3+10Li2O+10Na2O+0.1Er2O3 6. Er–0.5: 64.5P2O5+15Bi2O3+10Li2O+10Na2O+0.5Er2O3 8. Er–1.5: 63.5P2O5+15Bi2O3+10Li2O+10Na2O+1.5Er2O3 9. Er–2.0: 63.0P2O5+15Bi2O3+10Li2O+10Na2O+2.0Er2O3 2.2 Measurements

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7. Er–1.0: 64.0P2O5+15Bi2O3+10Li2O+10Na2O+1.0Er2O3

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The density measurements of present glasses were made using Archimede’s principle using water as immersion liquid. Refractive index (n) was estimated by using 1–bromo naphthalene (C10H7Br) as contact liquid with an Abbe refractometer. XRD measurements of

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BiP glasses were performed using RIGAKU X–ray diffractometer. The SEM with EDX photographs were carried out using Carl Zeiss EVO MA15 with EDAX (Oxford INCA Penta FETX3). The FTIR spectra were carried out at RT with 4 cm-1 spectral resolution with a BRUKER FTIR spectrometer. Solid state

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P NMR spectra were obtained using a JOEL

ECX400 DELTA2 NMR spectrometer with a 4 mm probe at 400 MHz. The time of 31

P NMR spectra were recorded in 128

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acquisition was 18 ms with pulse width 2.9 µs. The

scans and 5 s relaxation delay. The optical absorption measurements were made using JASCO V–770 spectrophotometer. The visible photoluminescence (PL) spectra in the range 520–640 nm and NIR PL spectra in the range 1400–1700 nm were carried out with FLS 980,

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Edinburg using 980 nm LD as excitation source.

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3. Results and Discussion 3.1 Chemical durability

The chemical durability of glasses was evaluated by using the value of ∆W%

= 
% [16], where W1 is the weight of the glass sample. Now the sample was kept in  a thermostatic water bath at 95 0C for 1 h and then cooled and dried at a temperature of 70 0C for 1 h. The weight of the dried sample is W2. This process of thermostatic water bath is repeated for 2 h and 3 h also. The results of the ∆W% for different concentrations of Er3+ doped 15Bi2O3 glasses are tabulated in Table 1 along with other physical parameters obtained using standard formulae [17].

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ACCEPTED MANUSCRIPT 3.2 X–ray diffraction (XRD) profiles The X–ray diffraction (XRD) spectra of studied BiP glass matrices were recorded in the range 100 ≤ 2θ ≤ 700. Fig. 1 depicts the 0.5 mol% of Er3+ doped BiP glasses at different Bi2O3 contents. The studied glass matrices did not show any crystalline peaks, but showed diffused pattern at lower scattering angles, which revealed amorphous nature of BiP glass

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samples. 3.3 Scanning electron microscope (SEM) with Energy dispersion spectroscopy (EDS)

The SEM micrographs with EDX of present studied Er3+ doped BiP glasses were recorded. Fig. 2(a) shows the SEM micrograph for Er–1.0 glass matrix. It was noted from

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Fig. 2(a) revealed that these glasses have regular morphology and have no particle aggregate reflecting amorphous nature of glasses. The information regarding elemental composition of

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the sample was obtained by the EDX. Fig. 2(b) shows EDX spectrum of Er–1.0 glass sample. 3.4 Fourier transform infrared (FTIR) spectra

The presence of functional and structural groups of prepared 0.5 mol% Er3+ doped BiP glass samples were analysed in the range 600–3800 cm-1 using transmission spectra, which were shown in Fig. 3. Several transmission bands were observed at ~960, ~1082, ~1163, ~1638, ~2307, ~2394, ~2922, ~3399 and ~3740 cm-1 from each infrared spectrum.

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Below are the results obtained from FTIR spectra regarding structural details. (A) The band at 960 cm-1 was attributed to the asymmetric stretching of P–O–P linkages with meta–phosphate group (Q2 units) [18]. (B) The band at 1082 cm-1 was resulted from the asymmetric stretching vibration mode

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of P–O–P non–bridging bond oxygen group [18]. (C) The band at 1163 cm-1 was related to (P–O-) vibrations in the orthophosphate

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groups [19].

(D) The band at 1638 cm-1 was due to the presence of P–O–H group [20]. (E) The bands at 2307, 2394 and 2922 cm-1 were due to the hydrogen bonding [21]. (F) The bands at 3399 cm-1 and 3740 cm-1 were due to symmetric stretching vibrations of hydroxyl groups (O–H) [22].

3.5 Magic angle spin nuclear magnetic resonance (MAS NMR) analysis 31

P solid state NMR is very attractive and advanced tool in analysing structures of

phosphate–type glasses. The classification of phosphate tetrahedra based on number of bridging oxygens was discussed in our previous article [23]. 31P solid state NMR spectra for different Bi2O3 contents and Er2O3 concentrations were shown in Figs. 4(a) and 4(b), 5

ACCEPTED MANUSCRIPT respectively. In the case of Bi–0 glass matrix, a dominant peak at -25.9 ppm was observed which is due to Q2 metaphosphate structural units. Bi–5 glass matrix reveals the co–existence of Q2 (-27.7 ppm) and Q1 (-2.1 ppm) tetrahedra. In the case of Bi–10 glass matrix, chemical shifts were observed at -25.2 ppm (Q2 tetrahedra) and at 1.5 ppm (Q0 tetrahedra). For Bi–15 glass matrix, the resulted signals were observed at -23.3 ppm and 1.6 ppm attributing to Q2

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and Q0 tetrahedra respectively [24]. Table 2 listed 31P solid state NMR data for studied glass matrices. It was noted that Bi–0, Bi–5, Bi–10 and Bi–15 glasses exhibiting dominant signals with chemical shifts at 25.9, -27.7, -25.2 and -23.3 ppm respectively which confirmed quantitative conformation of Q2 tetrahedra compared to other tetrahedra (Q3, Q1 and Q0). With the increase of Bi2O3,

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chemical shift was moved from -27.7 ppm (Q2) to -23.3 ppm (Q2), i.e., from more negative to less negative value due to the increase of ionicity of the non–bridging oxygen bonds [25].

with increasing Bi2O3 content.

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This result would suggest the transformation of structural units in the direction from Q2 to Q0

From Fig. 4(b) it was observed that, glass samples Er–0.5, Er–1.0, Er–1.5 and Er–2.0 exhibiting major signals with chemical shifts -24.71, -26.34, -27.26 and -29.09 ppm respectively corresponding to chain like Q2 metaphosphate structural units. From

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P solid

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state NMR data listed in Table 2, it was observed that as Er2O3 concentration increased, the major peak moved slightly to higher negative value. This might be due to increase of oxygen to phosphorous ratio with the increase of Er2O3 concentration. 3.6 Absorption spectra

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The optical absorption spectra of BiP glasses doped with Er3+ ions measured in the range 325–1700 nm and as a representative case, the absorption spectrum of the Er–1.0 glass

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is depicted in Fig. 5. All the Er3+ doped BiP glasses demonstrated similar absorption peaks as expected, centered at ~1534 nm, ~977 nm, ~797 nm, ~651 nm, ~543 nm, ~520 nm, ~487 nm, ~451 nm, ~407 nm, ~379 nm and 365 nm, correspond to the transitions originating from the 4

I15/2 ground state to the different excited states 4I13/2, 4I11/2, 4I9/2, 4F9/2, 4S3/2, 2H11/2, 4F7/2, 4F5/2,

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G9/2, 4G11/2 and 4G9/2 respectively [26]. The shape and peak positions of each transition for

the Er3+ doped glasses are very similar to those of other reported Er3+ doped glasses [14, 27, 28], indicating homogeneous incorporation of Er3+ ions in the glassy network without clustering and change in the local ligand field. The strong absorption peak in NIR region at ~980 nm, 4I11/2 level of Er3+ indicates that the glass can be excited efficiently by a 980 nm laser diode (LD). 6

ACCEPTED MANUSCRIPT 3.7 Oscillator strengths and Judd-Ofelt parameters The spectroscopic and laser parameters of RE doped glasses effectively investigated with the help of oscillator strengths and Judd–Ofelt theory (J–O) [29, 30]. Details of the theory and method were well described in earlier studies [22, 31], so only the results were presented in this section. Table 3 lists the experimental and calculated oscillator strengths

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(fexp, fcal) for the observed transitions along with root mean square deviations (δrms). δrms value was of the order of x10-6, which indicated the validity of the J–O theory for predicting the spectral intensities of Er3+ and the reliability of the calculations. From the table it is observed that, the transitions, 4I15/2→2H11/2 at 521 nm and 4I15/2→4G11/2 at 379 nm possess higher

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spectral intensities compared to the other transitions. These two transitions can be called as hypersensitive transitions which have followed the selection rules |∆S|=0, ∆L≤2 and ∆J≤2 [14].

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The intensity parameters, Ωλ (λ=2, 4, 6) of 0.5Er3+ doped different contents (0, 5, 10 and 15 mol%) of Bi2O3 and different concentrations (0.1, 0.5, 1.0, 1.5 and 2.0 mol%) of Er3+ doped 15 mol% Bi2O3 contained glasses were calculated and were presented in the Table 4. Previous studies have revealed that, the Ω2 parameters were indicative of the amount of covalent bond and were mostly sensitive to local structure and glass composition. The large

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value suggests a predominate environment of covalency and asymmetry between rare earth ions and ligands. As observed from table, the Ω2 parameter has increased from 6.56 to 8.34x10-20 cm2 with the increase of Bi2O3 content from 0 to 15 mol% indicating increasing degree of covalency and asymmetry of ligand field around Er3+ ion site. Similarly with the

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increase of Er3+ concentration from 0.1 to 2.0 mol%, Ω2 value increased upto 1.0 mol% and then decreased. The value of Ω2 for Er-1.0 glass was found to be 9.02x10-20 cm2, compared

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with other reported glasses [5, 14, 32, 33] as shown in Table 4. Values of Ω4 and Ω6 provide information on the rigidity and viscosity of the hosts.

However, compared with Ω2, structural information carried by Ω4 and Ω6 values were found nominal and sometimes inaccurate. Ω6 had a relation with the isomer shift (IS) of RE ions which reveals the 6S electron density of RE ion. Large value of Ω6 speculates the large value of emission bandwidth and spontaneous radiative probability of rare earth [34]. From Table 4, it was observed that with the increase of Bi2O3 content, Ω6 parameter also increased from 1.21x10-20 to1.53x10-20 cm2. This was due to the fact that influence of Bi–O bond on the local environment around Er3+ increases with increasing Bi2O3 content. But with the increase of Er3+ ion concentration from 0.1 to 2.0 mol%, Ω6 value initially increased and reached a 7

ACCEPTED MANUSCRIPT maximum value at 1.0 mol% and then decreased. This might be due to the fact that at higher concentrations of Er3+ ion, influence of Er–O dominates the Bi–O bond. The J–O parameters follow the trend as Ω2>Ω4>Ω6 uniformly for all the prepared glass samples similar to silicaborate [5], bismuth fluro-phosphate [14] and ZBLAN [32] glasses. As the spectroscopic quality factor (χ), Ω4⁄Ω6 usually indicates the lasing efficiency of the laser transition of Er3+ in

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the host glass, the relatively high χ value of the glass will benefit the radiative transition, which means a strong stimulated emission can be induced. In the present study, the χ value for Er–1.0 glass was 1.34 which was relatively higher than silicaborate [5], fluoro-phosphate [14] and ZBLAN [32] glasses and lower than tellurite [33] glasses. Er-1.0 glass was found a

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favourite glass, since it had higher Ωλ and χ values useful for strong stimulated emission. The J-O parameters have been used to predict certain radiative properties, such as

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radiative transition probabilities (AR), branching ratios (βR) and radiative lifetimes (τR) using formula given in ref [18]. Calculated radiative lifetimes (τR) of certain excited states and branching ratios (βR) of certain transitions of Er3+ doped BiP glasses are shown in Table 5. 3.8 Optical band gap

An important parameter to describe both crystalline and non–crystalline materials is the optical band gap energy. Davis and Mott theory [35] was used to evaluate the optical

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band gap energy of the amorphous materials through direct and indirect allowed transitions. In both transitions, electrons were raised to conduction band across the band gap from the valence band by the interaction with electromagnetic waves. The absorption coefficient α(ν)

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was found from the relation

α(ν) =



   





=2.303

(1)

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where A represents the absorbance at frequency ν and d is the thickness of the sample. The absorption edge for both direct and indirect band gaps is calculated from the relation: α(ν) =

  



(2)

where B is the band tailing parameter, Eg is the optical band gap energy, hν is the photon energy and r is the index number which determines the type of optical transition i.e., r=2 for indirect allowed transition and r=1/2 for direct allowed transition. The optical band gap of the direct and indirect allowed transitions was obtained by extrapolating the linear region of the curves to the zero absorption at (αhν)2 = 0 and (αhν)1/2 = 0 respectively and the band tailing parameter values were also obtained from the slope of the curves. The direct and indirect allowed optical band gaps for all the studied Er3+ doped BiP glasses were shown in Figs. 6a8

ACCEPTED MANUSCRIPT 6d and the values were listed in Table 6. It is observed that the Eg values were found to decrease with the increase of Bi2O3 content (except for Bi-5 glass) from 3.84 to 3.74 eV (Fig. 6a) and from 3.82 to 3.70 eV (Fig. 6c) for direct and indirect allowed transitions respectively. In the same manner, with the gradual increase of erbium content from 0.1 to 2.0 mol%, Eg values are shifted to the lower values (except Er-0.5 glass) i.e., from 3.71 to 3.64 eV (Fig. 6b)

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and from 3.68 to 3.60 eV (Fig. 6d) for direct and indirect allowed transitions respectively. The decrement of Eg may be due to the progressive increase in the population of non– bridging oxygen (NBO) atoms. This was due to the fact that, NBO units were excited with less energy than the bridging oxygens (BO) causing changes in the characteristic absorption

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[36]. Kundu et al. [37] have also observed same phenomenon in the case of direct band gap transitions estimated from Tauc’s plot. 3.9 Visible Photoluminescence (PL) spectra

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Excitation spectrum for the Er3+ doped BiP glasses was recorded under green emission wavelength (545 nm) at RT in the wavelength range 350–500 nm and it was quite similar to other reported Er3+ glasses [14, 38]. Since all the spectra are alike, as a representative case, the excitation spectrum of Bi–15 glass is shown in Fig. 7. Five excitation bands, 4I15/2 → 4G9/2, 4G11/2, 2G9/2, 4F5/2 and 4F7/2 corresponding to the band positions 364,

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379, 406, 450 and 488 nm respectively were observed. Among all the observed bands, the band, 4I15/2→4G11/2 positioned at 379 nm was found as the prominent band compared to other bands. Hence, the transition 4I15/2→4G11/2 positioned at 379 nm was used as the excitation wavelength to measure PL spectra.

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The visible PL spectra of 0.5Er3+ doped different contents (0, 5, 10 and 15 mol%) of Bi2O3 and different concentrations (0.1, 0.5, 1.0, 1.5 and 2.0 mol%) of Er3+ doped 15 mol%

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Bi2O3 contained glasses were investigated in the range 520–640 nm at room temperature under 379 nm excitation and the same are shown in Figs. 8a and 8b respectively. Two emission peaks, one at 530 nm (green) and the other at 546 nm (green) resulted from the transitions 2H11/2→4I15/2 and 4S3/2→4I15/2 respectively were detected in the visible PL spectra. Between the two observed emission transitions, the 4S3/2→4I15/2 transition was more intense and might be suitable for green laser applications. The partial energy level diagram of Er3+ doped BiP glasses was shown in Fig 8c. When an erbium ion was excited at 379 nm resonantly with the 4G11/2 level, it decays non–radiatively to the 2H11/2 level and thus populates the 4S3/2 level due to the small energy difference (~840 cm-1) from where the dominant green emission was observed. The intensity of green emission (546 nm) was 9

ACCEPTED MANUSCRIPT increased with the increase of Bi2O3 content from 0 to 15 mol%. On the other hand, with the increase of Er3+ concentration from 0.1 to 2.0 mol%, the emission of 4S3/2 level (green emission) was increased from 0.1 mol% and reaches maximum at 1.0 mol% and then decreased from 1.0 to 2.0 mol%. This might be due to energy migration among Er3+ ions. Among all the studied glasses Er–1.0 glass showed higher emission intensity which might be

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useful for green emission laser. 3.10 Visible decay profiles of 4S3/2 level

Decay curves of 4S3/2 level of Er3+ ions were measured for all the prepared BiP glasses by exciting at 379 nm and by monitoring the emission at 545 nm and were shown in Figs. 9a

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and 9b for different contents of Bi2O3 and different concentrations of Er3+ ions respectively. All the decay curves exhibited non–exponential nature. The experimental lifetimes (τexp) of

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the 4S3/2 level were determined using the decay curves by taking first e-folding times of the decay curves.

The measured decay lifetimes calculated from the spectra shown in Fig. 9a were 6.62, 6.68, 6.79 and 7.21 µs for Bi–0, Bi–5, Bi–10 and Bi–15 glasses, respectively. The decay times of 4S3/2 level were found to increase with the increase of Bi2O3 content. Similarly, the

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fluorescent decay times for the concentration variation of Er3+ ions (Fig. 9b) were found to be 5.86, 7.21, 7.74, 7.25 and 7.29 µs for Er-0.1, Er-0.5, Er-1.0, Er-1.5 and Er-2.0 respectively. It is noted that, fluorescence decay times increases with the increase of Er3+ concentration upto 1.0 mol% and then decreased for 1.5 and 2.0 mol% of Er3+. This could be related to energy

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transfer process between Er3+ ions. Among all the prepared Er3+ doped BiP glasses Er-1.0 glass exhibited higher lifetime (7.74 µs).

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3.11 NIR photoluminescence at 1.53 µm The emission band at 1.53 µm is the most important for the applications in optical

communication systems and IR laser applications. The NIR PL spectra was recorded for 0.5Er3+ doped BiP glasses for various Bi2O3 contents (0, 5, 10 and 15 mol%) and different concentrations (0.1, 0.5, 1.0. 1.5 and 2.0 mol%) of Er3+ doped 15 mol% Bi2O3 contained glasses under the excitation of 980 nm to study the both compositional and concentration effect. The composition (Bi2O3) and concentration (Er3+) dependence PL spectra along with partial energy level diagram were shown in Figs. 10a - 10c. The PL band typically exhibits asymmetric shape at ~1534 nm having overall features covering 1400-1700 nm regions. This band consists of both electric and magnetic dipole components since it satisfies the selection 10

ACCEPTED MANUSCRIPT rule ∆S = ∆L= 0, ∆J= +1. The sharp peaks observed at 6485 and 6519 cm-1 correspond to the magnetic dipole components and broad peaks observed at 6265 and 6662 cm-1 correspond to the electric dipole components. When Er3+ ions were excited at 980 nm excitation resonantly with 4I11/2 level, the ions non–radiatively decay to the next lower energy level 4I13/2 and due to the longer lifetime (~ms), population inversion was achieved which enabled the stimulated

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emission from 4I13/2 to 4I15/2 level (Fig. 10c). The emission intensity of the spectra (Fig. 10a) was increased with the increase of Bi2O3 content from 0 to 15 mol%. This might be due to the fact that reduction of OH– with the substitution of Bi2O3. Further no shift (red or blue) was observed in the peak position. From Fig. 10b, it is seen that emission intensity has increased with the increase in Er3+ concentration from 0.1 to 1.0 mol% and further decreased for higher

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concentrations. It was found that, with the increase in Er3+ ion concentration, aggregation of more number of Er3+ ions took place in the 4I11/2 energy level leading to luminescence

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quenching beyond 1.0 mol%. Among all the studied glasses, Er–1.0 glass showed higher emission intensity for 1534 nm emission band which was in the range of 1400–1700 nm covers the whole low loss communication window (S, C and L bands). 3.12 NIR decay profiles of 4I13/2 level

The decay profiles of the 4I13/2 level of Er3+ ions are important for optical amplifier.

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Long lifetime of the metastable state (4I13/2) is the key factor in the success of Er3+ doped fiber amplifiers in the optical communication. The decay profiles were obtained for all the studied glasses (different Bi2O3 contents and different Er3+ ion concentrations) monitored at 980 nm LD excitation and 1534 nm emission. All the decay curves have exhibited non-

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exponential nature. Fig. 11a depicts the decay lifetime spectra of 4I13/2 level with Bi2O3 variation from 0 to 15 mol%. The experimental lifetimes (τexp) were found to be 0.53, 0.78,

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1.14 ms and 1.76 for Bi–0, Bi–5, Bi–10 and Bi–15 glasses respectively. It was found that with the increase of bismuth content, lifetime values have also increased. The increment in the lifetime of 4I13/2 level is might be due to the lowering of phonon energy of the glass with substitution of Bi2O3. The decay profiles of 4I13/2 level for different Er3+ concentrations (0.1, 0.5, 1.0, 1.5 and 2.0 mol%) were shown in Fig. 11b. The τexp values for this level were found to be 2.40, 1.76, 1.75, 1.25 and 1.04 ms for Er–0.1, Er–0.5, Er–1.0, Er–1.5 and Er–2.0 glass matrices respectively. It was observed that τexp values decreased from 2.40 to 1.04 ms with the rise of Er3+ concentration from 0.1 to 2.0 mol%. The shortening of lifetime of this level was likely due to the increase of energy transfer between neighbourhood Er3+ ions and Er3+ ions to quenching centres (OH– groups) [39]. 11

ACCEPTED MANUSCRIPT 3.13 Absorption and emission cross–sections Absorption cross–sections (σa) and emission cross–sections (σe) are key parameters to evaluate potential lasing applications. Absorption cross–section (σa) was evaluated by using Beer– Lambert’s equation using absorption spectra of Er3+ doped BiP glasses for 4I15/2→4I13/2

. ∗!"(λ)

σa =

%&

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transition at 1.53 µm. (3)

where OD(λ) is the optical density, N is the Er3+ ion concentration, and ' is the sample thickness. According to Mc–Cumber theory [40], the stimulated emission cross section is ()) *+

,

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σe = σa(λ)*exp(

(4)

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where h and k are the Planck’s and Boltzmann’s constants respectively and - is the net free energy required to excite Er3+ ion from the 4I15/2 level to 4I13/2 level at temperature T. Fig. 12 shows the absorption and emission cross-section spectra for Er-1.0 glass and these values are found to be 8.54x10-21 cm2 and 8.98x10-21cm2 respectively. The σa and σe values were determined for all the studied BiP glasses and were presented in Table 7. The spectrum of Mc–Cumber theory well fits to the experimentally measured one. It is evident from the table

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that the emission cross–section was high in the Er–1.0 glass with the value of 8.98x10–21cm2 which was comparable to those obtained for Er3+ doped bismuth fluoro-phosphate glasses 5.3x10-21cm2 [14] silica borate glasses 5.10x10-21cm2 [5]; telluroborate glasses 6.85x10-21cm2 [7] and lower than that of germanium-silicate glasses 9.55x10-21cm2 [41] and chalcogeneide

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glasses 15.73x10-21cm2 [42]; The large value of emission cross section indicate that the Er-

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1.0 glass is a promising material for lasing action. 3.14 Gain properties

The optical gain cross–section G(λ) can be calculated from the σa and σe values using

the formula:

G(λ) = γσe(λ) – (1–γ)σa(λ)

(5)

where γ is the population inversion parameter. The evolution of G(λ) for Er–1.0 glass matrix was shown in Fig. 13 as a function of γ as 0, 0.2, 0.4, 0.6, 0.8 and 1, respectively. It can be seen from figure that, gain become positive for the population inversion of 0.4 in the spectral range 1564–1635 nm (L band). It is noted that the optical gain cross–section increased and the gain extends to longer wavelength with the increase of population inversion parameter (γ) indicating as promising materials for broadband amplification. 12

ACCEPTED MANUSCRIPT Table 8 presents emission peak positions (λP), full width at half maximum (FWHM), emission cross-section (σem), gain bandwidth, measured lifetime (τexp) and optical gain for the 4

I13/2 level of Er3+ ion. FWHM and σem are important parameters in an optical amplifiers to

achieve broadband and high-gain amplification. In the present work, the FWHM not changed significantly with Bi2O3 suggesting that the increase of Bi2O3 do not affect much the ligand

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field from one Er3+ site to another and thus cannot lead to more inhomogeneous broadening of the emission spectra. When Er3+ ion concentration increased from 0.1 to 0.5 mol%, FWHM value was increased from 29 to 41 nm and then decreased to 38 nm for 1.0 mol% and 49 nm for 2.0 mol%. The observed changes in FWHM with increasing Er3+ ion concentration

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could be due to two factors: The first is the radiative energy transfer between Er3+ ions induced by the overlapping of the absorption and emission bands. Another one is the energy migration among Er3+ ions [43]. The larger value of FWHM could be interesting for

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wavelength-division multiplexing applications. The gain bandwidth is an important parameter to characterise laser materials at 1.53 µm band. The bigger the product of σem and τexp, the better the gain characteristic of Er3+ doped fiber amplifier yields. It can be observed from the table that among all the studied BiP glasses Er-1.0 glass had higher gain bandwidth of 332 cm3. Er–1.0 glass had higher value than those of bismuth fluoro-phosphate [14] lead borate

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[44] glasses, where as lower than those of silica borate [5] and zinc borate [38] glasses. Further it is also noticed that, optical gain (G) which was the product of σem and τexp. Er–1.0 glass (15.29x10-24cm2 s) showed higher in magnitude than other prepared glasses. It was also higher than other reported bismuth fluoro-phosphate (12 x10-24cm2 s) [14], ZBLAN (0.6x10cm2 s) [32] and silica borate (7.43x10-24cm2 s) [5] glasses. Higher values of gain bandwidth

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24

and optical gain indicate that they are the promising materials for broadband light sources and

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broadband amplifiers.

The stimulated absorption cross–sections, emission cross sections, optical gain and

gain bandwidth, are important properties which are essential for amplification and lasing of optical signal. In the present work, these properties were studied and found higher in Er–1.0 glass matrix compared to other prepared glasses. Hence, Er–1.0 glass may be suggested for active media for optical fiber lasers and amplifiers. 4. Conclusions In the current study, erbium (Er3+) ion doped bismuth phosphate (BiP) glasses of chemical compositions, (79.5–x)P2O5+10Li2O+10Na2O+0.5Er2O3+xBi2O3 where x=0; 5; 10; and 15 mol%; and (65–y)P2O5+15Bi2O3+10Li2O+10Na2O+yEr2O3 where y= 0.1; 0.5; 1.0; 13

ACCEPTED MANUSCRIPT 1.5; and 2.0 mol% were fabricated by melt quenching technique. Composition (Bi2O3) and concentration (Er2O3) effects on Er3+ doped different Bismuth phosphate glasses were studied with the help of structural and optical measurements. XRD and SEM confirmed the noncrystalline nature of studied BiP glasses. Using FTIR and

31

P solid state NMR spectra, the

functional groups that are present were identified. From absorption spectra, Judd-Ofelt (JO)

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intensity parameters and energy band gaps were determined. The results of J-O theory analysis showed that, Er-1.0 glass matrix found higher covalency (Ω2) and spectroscopic quality factor (χ) with 9.02x10-20 cm2 and 1.34 respectively than the other prepared BiP glasses. Energy band gaps were decreased with the increase of both composition and concentration of Bi2O3 and Er2O3 respectively. The visible PL spectra of studied BiP glasses

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showed intense and broad emission at 545 nm (green) for 4S3/2→4I15/2 transition with the excitation 379 nm. Among all the studied BiP glasses, Er-1.0 glass showed higher emission

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intensity which might be useful for green laser applications. The NIR luminescence behaviour in the wavelength region 1400-1700 nm at 980 nm excitation was also observed. Absorption and stimulated emission cross-sections were determined using Mc-Cumber theory. The suitability for optical amplifier applications and NIR laser have been discussed with parameters such as stimulated emission cross-section (σe), gain bandwidth (∆G), optical

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gain (G). The decay curves for both 4S3/2 (visible) and 4I13/2 (NIR) levels are discussed and are exhibiting non-exponential nature for all the studied BiP glasses. Among all the BiP glasses, Er-1.0 glass exhibited higher σe, ∆G and G values suggesting the suitability for optical amplifier and NIR laser applications.

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Acknowledgment

One of the authors S. Damodaraiah would like to thank University Grants

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Commission (UGC), New Delhi for the sanction of Junior Research Fellowship (JRF) under Research Fellowship in Science for Meritorious Students (RFSMS) scheme. The authors acknowledge MoU-DAE-BRNS Project (No. 2009/34/36/BRNS/3174), Department of Physics, S.V. University, Tirupati, India for extending experimental facility.

14

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18

ACCEPTED MANUSCRIPT

Table 1

index (n)

Concentration (N, x 1020 ions/cm3)

Inter

Polaron

Dielectric

Reflection

Molar

constant

loss

refraction

(ε)

(R%)

(Rm, cm3)

0.076

2.725

6.030

0.224

2.725

22.29

0.372

19.47

17.65

Field

nuclear

radius

distance

0

(rP, A )

(ri, A0)

3.31

1.651

0.084

19.82

49.19

Er-0.5

3.34

1.651

0.422

11.57

28.72

Er-1.0

3.58

1.651

0.902

8.98

Er-1.5

3.60

1.651

1.355

7.84

Er-2.0

3.63

1.651

1.818

7.11

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15

-2

∆W (mg/g)

1h

2h

3h

12.79

0

0

0

6.030

12.71

0

0

0

2.725

6.030

11.90

0

0

0

0.488

2.725

6.030

11.88

0

0

0

0.593

2.725

6.030

11.81

0

0

0

(F, x 10 cm )

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Er-0.1

strength

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(ρ, g/cm3)

RE ion

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Glass

Density

Refractive

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Physical and chemical parameters of the 15 mol% of Bi2O3 contained different concentrations of Er3+ doped BiP glasses.

ACCEPTED MANUSCRIPT Table 2 Chemical shifts (δ) (ppm) and structural units of

31

P MAS NMR spectra of various contents of

Bi2O3 and different concentrations of Er2O3 doped BiP glass matrices.

Chemical shift Glass

Structural units

-25.9

Bi-5

-27.7 -2.1

Bi-10

-25.2 1.5 -23.3

Q2

Q1

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Bi-15

Q2

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Bi-0

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δ (ppm)

Q2 Q0 Q2

Q0

Er-0.5

-24.7

Q2

Er-1.0

-26.3

Q2

Er-1.5

-27.3

Q2

Er-2.0

-29.1

Q2

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1.6

ACCEPTED MANUSCRIPT

Table 3 Experimental (fexp) and calculated (fcal) spectral intensities (x10-6) of different absorption bands of Er3+ doped in different concentrations and different contents of Bi2O3 in BiP

Energy

Bi-0

Bi-5

Bi-10

Bi-15

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glass matrices.

Er-0.1

Er-0.5

fcal

fexp

fcal

fexp

fcal

fexp

fcal

4

5.01

4.27

4.32

3.60

3.78

2.58

2.99

2.03

2.40

2.50

1.95

1.99

1.68

1.52

1.23

1.17

1.03

I9/2

0.66

0.86

0.67

0.82

0.65

1.13

0.55

F9/2

6.41

6.45

6.50

5.81

6.24

6.31

1.71

1.68

1.26

1.38

1.01

0.87

I13/2 I11/2

4 4 4

S3/2

2

H11/2

4

F7/2

18.15 18.37

19.41 19.21

23.00 22.77

fcal

Er-1.5

Er-2.0

fexp

fcal

fexp

fcal

fexp

fcal

fexp

fcal

2.72

2.99

2.03

3.18

2.32

3.03

1.93

2.74

1.53

1.16

1.33

1.17

1.03

1.08

1.27

0.65

1.08

0.96

0.86

0.97

0.71

0.64

0.55

0.97

0.43

0.44

0.19

0.45

0.42

0.63

5.19

5.25

4.51

4.43

5.19

5.25

3.25

3.31

3.01

3.09

3.40

3.51

0.74

0.66

0.85

1.02

0.74

0.66

0.83

0.86

0.74

0.70

0.53

0.49

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4

fexp

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fexp

I15/2 →

23.20 22.85

18.78 18.63

23.20 22.85

22.17 22.32

21.20 21.20

21.40 21.14

6.51

5.31

5.54

4.25

4.43

3.28

3.50

4.23

4.15

3.28

3.50

3.24

3.35

2.76

2.85

2.46

2.48

F5/2

2.07

1.57

1.72

1.29

1.47

0.82

1.34

0.61

0.99

0.96

1.34

0.61

1.45

0.81

0.95

0.65

0.78

0.46

G9/2

2.37

2.41

1.83

2.02

1.25

1.46

1.10

1.13

1.52

1.51

1.10

1.13

1.09

1.24

1.01

1.03

0.81

0.82

2 4

G11/2

4

G9/2

δrms

32.34 32.26 4.43

4.19

±0.40

33.74 33.82 3.86

3.83

±0.36

39.81 40.03

EP

6.35

4

39.89 40.20

AC C

4

SC

level

Er-1.0

4.85

4.40

±0.49

4.23

3.68

±0.45

32.42 32.77 2.54

2.87

±0.20

39.89 40.20 4.23

3.68

±0.45

39.22 39.27 2.46

2.15

±0.35

37.50 37.33 2.32

2.05

±0.39

37.19 37.23 3.11

2.44

±0.44

ACCEPTED MANUSCRIPT Table 4 Judd-Ofelt intensity parameters (Ωλ, x10-20 cm2) of Er3+ doped different BiP glass matrices. Glass Code

Ω2

Ω4

Ω6

Ω4 / Ω6

Bi-0

6.56

1.23

1.21

1.01

Bi-5

6.87

1.26

1.22

1.03

Bi-10

7.97

1.61

1.45

1.11

Bi-15

8.34

1.95

1.53

1.27

Er-0.1

6.99

1.69

1.35

1.25

Ω2 >Ω4 >Ω6

present work

Er-0.5

8.34

1.90

1.53

1.27

Ω2 >Ω4 >Ω6

present work

Er-1.0

9.02

2.39

1.78

1.34

Ω2 >Ω4 >Ω6

present work

Er-1.5

8.53

1.79

1.66

1.07

Ω2 >Ω4 >Ω6

present work

Er-2.0

8.22

1.59

1.47

1.08

Ω2 >Ω4 >Ω6

present work

Silica borate

3.16

1.32

0.99

1.33

Ω2 >Ω4 >Ω6

[5]

Fluoro-phosphate

4.90

1.37

1.27

1.08

Ω2 >Ω4 >Ω6

[14]

ZBLAN

2.91

1.27

1.11

1.14

Ω2 >Ω4 >Ω6

[32]

1.81

1.64

Ω2 >Ω4 >Ω6

[33]

2.98

Ω2 >Ω4 >Ω6

present work

RI PT

Ref

Ω2 >Ω4 >Ω6

present work

Ω2 >Ω4 >Ω6

present work

Ω2 >Ω4 >Ω6

present work

SC

M AN U

TE D

EP 8.95

AC C

Tellurite

Trend

ACCEPTED MANUSCRIPT

Table 5

transitions of Er3+ doped different BiP glasses.

4

Glass

τR G11/2

4

F5/2

4

F7/2

4

S3/2

4

4

F9/2

I9/2

Bi-0

26

161

128

258

329

2736

Bi-5

28

190

147

314

365

3015

Bi-10

31

233

164

490

341

2598

Bi-15

35

294

204

654

410

3067

Er-0.1

34

254

195

428

477

Er-0.5

35

294

204

654

410

Er-1.0

35

312

248

504

628

Er-1.5

39

366

282

627

Er-2.0

42

415

293

604

I11/2

2807

4

I13/2

8496

4

S3/2→4I15/2

∆E

βR (%)

∆E

βR (%)

6522

100

18426

66.9

8403

6520

100

18409

66.8

4423

7037

6521

100

18403

66

5305

6614

6521

100

18403

65.8

3945

4148

7513

6521

100

18365

66.9

3067

5305

6614

6521

100

18403

65.8

5345

4433

5780

6519

100

18406

66.9

5577

5214

6188

6521

100

18386

66.8

4686

6443

6849

6521

100

18379

66

TE D

3271

EP 675

AC C 872

4

I13/2→4I15/2

SC

4

M AN U

Matrix

RI PT

Calculated radiative lifetimes (τR, μs) of certain excited states, branching ratios (βR, %) and energy difference (∆E, cm-1) of certain

ACCEPTED MANUSCRIPT Table 6 The direct and indirect allowed bandgaps (Eg, eV) of Er3+ doped different BiP glass matrices. Eg (eV)

Glass matrix code

Bi-5

3.89

Bi-10

3.82

Bi-15

3.74

Er-0.1

3.71

Er-0.5

3.74

3.82 3.87

3.80

Er-1.0 Er-1.5

EP AC C

3.68 3.70

3.68

3.64

3.66

3.62

3.64

3.60

TE D

Er-2.0

3.70

SC

3.84

M AN U

Bi-0

Indirect

RI PT

Direct

ACCEPTED MANUSCRIPT Table 7 Using Mc-Cumber theory, the calculated values of the absorption cross-section (σa x10-21 cm2) and emission cross-sections (σex10-21 cm2) for the 4I13/2 level around 1.53 μm of Er3+ doped BiP glasses.

Bi-5

5.93

Bi-10

6.21

Bi-15

6.98

Er-0.1

6.15

Er-0.5

6.98

Er-1.0

8.54

Er-1.5

7.18

Er-2.0

6.68

RI PT

5.36

5.74 6.13 6.28

SC

Bi-0

σe

7.13 6.21

M AN U

σa

AC C

EP

TE D

Glass

7.13 8.98 7.24 6.74

ACCEPTED MANUSCRIPT Table 8 Full width at half maximum (FWHM, nm), emission cross-section (σem (λ) x10-21 cm2), gain bandwidth (FWHM x σem x10-28 cm3), lifetime (τexp, ms) and optical gain (σem (λ) x τexp x 1024 cm2 s) for the 4I13/2 level of Er3+ ion doped in BiP glasses.

FWHM

σem (λ)

τexp

I13/2 → 4I15/2

Bi-0

1534

40

5.36

0.53

Bi-5

1534

40

5.57

0.78

Bi-10

1534

41

6.41

Bi-15

1534

41

6.86

Er-0.1

1534

29

6.34

Er-0.5

1534

41

Er-1.0

1534

Er-1.5 Er-2.0

212

2.84

223

4.34

RI PT

λP

Optical gain (G)

SC

Glass

263

7.30

1.76

281

12.07

2.40

184

15.21

6.86

1.76

281

12.07

38

8.74

1.75

332

15.29

1534

44

6.89

1.25

303

8.61

1534

49

6.67

1.04

326

6.94

EP

TE D

M AN U

1.14

AC C

4

Transition

Gain Bandwidth (∆G)

ACCEPTED MANUSCRIPT Figure Captions: Fig. 1. XRD pattern of 0.5Er3+ doped BiP glass matrices for various Bi2O3 contents. Fig. 2. (a) SEM image (b) EDX spectrum of Er-1.0 glass matrix. Fig. 3. FTIR spectra of 0.5Er3+ doped BiP glasses for various Bi2O3 contents.

RI PT

Fig. 4. 31P MAS NMR spectra of (a) 0.5Er3+ doped BiP glasses for various Bi2O3 contents and (b) different concentrations of Er3+ doped BiP glasses contained 15 mol% of Bi2O3. Fig. 5. Optical absorption spectra of 15 mol% Bi2O3 contained Er-1.0 glass matrix.

SC

Fig. 6. Tauc’s plot as a function of energy (eV) for (a, b) direct allowed transitions and (c, d) indirect allowed transitions of Er3+ doped BiP glasses for different compositions of Bi2O3 and concentrations of Er2O3. Fig. 7. Excitation spectrum of 0.5Er3+ doped Bi-15 glass matrix.

M AN U

Fig. 8. Visible emission spectra of (a) 0.5Er3+ doped BiP glasses for various Bi2O3 contents, (b) different concentrations of Er3+ doped 15 mol% of Bi2O3 contained BiP glasses, and (c) partial energy level diagram. Fig. 9. Decay profiles of 4S3/2 level of (a) 0.5Er3+ doped BiP glasses for various Bi2O3 contents and (b) different concentrations of Er3+ doped BiP glasses contained 15 mol% of Bi2O3.

TE D

Fig. 10. NIR emission spectra of (a) 0.5Er3+ doped BiP glasses for various Bi2O3 contents, (b) different concentrations of Er3+ doped 15 mol% of Bi2O3 contained BiP glasses, and (c) partial energy level diagram

EP

Fig. 11. Decay profiles of 4I3/2 level of (a) 0.5Er3+ doped BiP glasses for various Bi2O3 contents and (b) different concentrations of Er3+ doped BiP glasses contained 15 mol% of Bi2O3.

AC C

Fig. 12. Absorption and emission cross-section of the Er-1.0 glass matrix for the 4I13/2→4I15/2 level calculated from Mc-Cumber theory. Fig. 13. Gain co-efficient of Er-1.0 glass for the 4I13/2→4I15/2 level as a function of wavelength

AC C

EP

TE D

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SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 1

AC C

EP

TE D

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ACCEPTED MANUSCRIPT

Fig. 2(a)

Fig. 2(b)

AC C

EP

TE D

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ACCEPTED MANUSCRIPT

Fig. 3

AC C

EP

TE D

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ACCEPTED MANUSCRIPT

Fig. 4(a)

AC C

EP

TE D

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ACCEPTED MANUSCRIPT

Fig. 4(b)

AC C

EP

TE D

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ACCEPTED MANUSCRIPT

Fig. 5

AC C

Fig. 6(a)

EP

TE D

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RI PT

ACCEPTED MANUSCRIPT

Fig. 6(b)

AC C

EP

Fig. 6(c)

TE D

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SC

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ACCEPTED MANUSCRIPT

Fig. 6(d)

AC C

EP

TE D

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SC

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ACCEPTED MANUSCRIPT

Fig. 7

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 8(a)

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

Fig. 8(b)

Fig. 8(c)

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 9(a)

AC C

EP

TE D

M AN U

SC

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ACCEPTED MANUSCRIPT

Fig. 9(b)

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 10(a)

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

Fig. 10(b)

Fig. 10(c)

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 11(a)

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

Fig. 11(b)

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

Fig. 12

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

Fig. 13

ACCEPTED MANUSCRIPT Highlights:
Er3+ doped bismuth phosphate (BiP) glasses were prepared by melt quenching technique.
Er3+ doped BiP glasses exhibited intense green emission at 379 nm excitation (4S3/2→4I15/2).

RI PT


Lasing transition in this Er3+ doped BiP glasses is 4I13/2→4I15/2 (1.53 μm).
Absorption and emission cross-sections were estimated by Mc-Cumber theory.


Gain properties have been studied for 1.53 μm for developing solid-state optical

AC C

EP

TE D

M AN U

SC

amplifiers.