Effect of Vanadium on Structural and Optical Properties of Bo- rate Glasses Containing Er3+ and Silver Nanoparticles

Glass samples (59.5 – x) B2O3 – 20Na2O – 20CaO – xV2O5 – Er2O3 – 0.5AgCl (x = 0 – 2.5 mol%) were prepared using melt – quenching method to investigate the structural and optical properties of the glass. The structural of the glass were characterized by using XRD, TEM and FTIR, meanwhile the optical properties were characterized by UV – VIS absorption. The XRD patterns confirmed the amorphous nature of the prepared glass samples. FTIR confirmed the presence of VO4, VO5, BO3, and BO4 vibration, and this result showed NBO increased with increasing vanadium concentration. The UV – Vis – NIR spectra exhibits six absorption band centered at 490, 520, 540, 660, 800, and 980 nm. The optical band gap (Eopt), Urbach energy and refractive index shown decrease, increase and increase, respectively. The Judd – Ofelt intensity parameter reveal the trends was Ω2 > Ω4 > Ω6. There are three emission bands at 516 nm, 580 nm, and 673 nm which are represented by 2H11/2 – 4I15/2, 4S3/2 – 4I15/2, and 4F15/2 – 4I15/2, respectively under 800 nm excitation was obtained.

former glass while low concentration vanadium can be considered as modifier [7,10]. In this mixed glass former effect composition has attracted interest because of their interesting structural and physical properties.
Besides, vanadium is one of the approaches to overcome clustering due to high concentration of erbium. Normally, to achieve strong emission ,high concentration of erbium is required [9], but when high doping level of erbium may cause clustering, which leads to luminescence quenching and large non-radiative losses [10]. Thus, there are several approaches to overcome this issue which are heat-treated to produce glass -ceramic, introduce metallic nanoparticle [9] and co -doped with various rare -earth ions or transition metal [13,14]. Previous reports confirmed that the emission intensity is stronger for system erbium ion -doped glasses co -doped with other rare earth such as Tm 3+ , Nd 3+ , and Yb 3+ compared with single erbium ion doped glass. Thus, the emission could be achieved through the introduction of both co -doping rare -earth with transition and metallic nanoparticles (NPS).
The participation of vanadium ion in radiative transitions within the glass network has been studying in the emission spectra of 40Na2O -54SiO2 -(5 -x) ZrO2 -Ho2O3 -xV2O5 [11] and 40Na2O -54SiO2 -(5 -x) ZrO2 -Sm2O3 -xV2O5 glasses [13]. An additional band appeared at 636 nm and 1095 nm due to the transition 2 B2 → 2 Bg and 2 B2 → 2 Eg when V2O5 was added. The addition of V2O5 in a host matrix has been suggested to improve luminescence efficiency and lower phonon energies. Hence, the concentration V2O5 was believed to be the local environment of rare-earth ions in the oxides glass not only dependent on the composition of the host matrix. Thus, the concentration of vanadium may contribute to different crystal field strength. There are several studies regarding the emission properties of V2O5 doped rare -earth glass, but further research is required to facilitate a better understanding of the role V2O5 in modifying of glasses.
In this paper, the effect of vanadium on the structural and optical properties in the (59.5 -x) B2O3 -20Na2O -20CaO -xV2O5 -Er2O3 -0.5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) glasses were studied. The structural properties were studied by X -ray diffraction (XRD), the fourier transformed infrared (FTIR) and transmission electron microscopy (TEM). The Uv -Vis spectrometer and photoluminescence spectrometer (pL) were used to study the absorption and luminesce spectra of the glass samples. Judd -Ofelt intensity parameter were calculated based on absorption spectra. Additionally, the radiative properties including effective band width, radiative transition probability, radiative lifetime and branching ratio were measured and analyzed.

Preparation of Glasses
Glass samples with the composition of (59.5 -x) B2O3 -20Na2O -20CaO -xV2O5 -Er2O3 -0.5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) was prepared the by conventional melt quenching method. This composition enables the formation of transparent glass suitable for optical applications [7]. The appropriate amount of analytical grade commercial powder boron oxide (B2O3), sodium carbonate (Na2CO3), calcium carbonate (CaCO3), vanadium oxide (V2O5), erbium oxide (Er2O3), silver chloride (AgCl) (purity ≥ 99 %) was mixed and weighed homogeneously. At 1200 ˚C, the homogeneous mixture melted in alumina crucibles for one hour. Then, the samples were quenched into a stainless plate and mould. The samples were annealed at 300˚C for three hours in another furnace. After three hours, the furnace will automatically stop the process and reduced the temperature by itself gradually until room temperature. This process allowed the samples to cool down. The glass samples were polished using sandpapers to get a parallel opposite surface with thickness approximately five mm for optical absorption and photoluminescent spectroscopy. The glass samples were powderized for X-ray diffraction (XRD), transmission electron microscopy (TEM) and infrared (IR) absorption characterization.

Characterization of Glasses
The glasses were examined by X -Ray Diffraction analysis using X'Pert Pro Panalytical diffrection to confirm the amorphous present in the samples. The formation crystalline plane in silver nanoparticles confirmed using Transmission electron microscopic (TEM). A small amount of powder samples dispersed into acetone liquid using ultrasonic bath. The solution was placed onto copper grid and allowed to dry before it was ready to characterization. Archimedes principle used to determine the density of the glass samples. The immersion medium was toluene [14,15] at room temperature. The density of the glass samples was calculated standard relation 1: (1) Where wa and wb are the glass samples weight in the air and the toluene respectively while ρ and ρo are a density of the glass samples and density of toluene (0.8669 gcm -3 ) [16,17]. The values of molar volume (Va) were calculated using equation 2; (2) Where Mv is the molar mass of the samples [17]. A Perkin Elmer UV-Vis-NIR Spectrophotometer in the range 200 nm -1000 nm was used to record the optical absorption spectra at room temperature. The functional group within the range 400 cm -1 -1600 cm -1 with 4 cm -1 at room temperature were investigated by the IR absorption spectra of the glass samples. The Perkin Elmer model Spectrum One FTIR spectrometer was used to record the glass powder sample's IR absorption spectra. The powder glass samples were mixed with KBr at a fixed ratio 1:80. The mixed powder was pressed into pallet through hand press. The visible up-conversion emission measurement was carried out in the wavelength region 200 -900 nm at room temperature by Perkin LS-55 luminesce spectrometer in which a pulsed Xenon lamp operates as source of excitation.

Samples (mol%)
Density (  The changes of molar mass and molar volume impact the density of the glass, and usually density and molar volume show contracting behavior. However, in the cases of study, the density and molar volume display same behavior, where both values increased with addition of vanadium. Others borate glass system also reported this behavior [5,23]. The mass of B2O3 (M = 69.63 g mol -1 ) is lighter compared with V2O5 (M = 181.88 g mol -1 ). It can be concluded, the increase in density was due to replacement of lighter molecular (B2O3) with a heavier molecular (V2O5). Thus, the non -bridging oxygen increased with increasing V2O5 content.
The borate group consist of many B -O bonds and Vanadate groups contain various of V -O bonds. The bond length of BO3 and BO4 were 1.36Å and 1.47Å [19], respectively. While the previous classical molecular (MD) stimulation research reported that, the bond length of V 5+ -O (1.81 -1.92 Å) was slightly longer than the bond length of V 4+ -O (1.74 -1.85 Å) [20]. The bonds in borate group are shorter than bonds in vanadate group. Thus, replacement of shorter B -O bond length with longer V -O bond length increase the molar volume and open the network structure of the glass samples.

IR Spectra
There are three mainly active infrared region for B2O3 -V2O5 [26,27]. The group of bands that occur around 500-750 cm -1 is due to bending of B -O -B linkages in the borate network. The bands lie between 800 -1200 cm -1 is due to asymmetric vibration of BO4 units. The third group is due to the asymmetric stretching relaxation of the B -O band of triagonal BO3 units, and the band lies between 1200 -1450 cm -1 . Other studies also reported the same results [21,23].
IR absorption spectra for (59 5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%), were recorded in 400 -1600 cm -1 region at room temperature is shown in the figure 4(a). Figure 4(b) show the deconvolution of spectrum at x = 1.0 mol% glass sample. Based on the figure 4, the vibrational modes of the borate network seen like to previous research [5]. The first region, the band at 1391 -1407 cm -1 was attributed to the stretching vibration of NBO bond from metaborate, orthoborate and pyroborate of BO3 unit. The band correlated to stretching vibration of B -O bonds in pentaborate, triborate, and tetraborate group of BO4 units is located at about 927 -1205 cm -1 . Mohamed et al [5] report that, region at 990 -1024 cm -1 is overlapping with the vibration from VO5 trigonal bipyramids unit of the V = O. They assumed that the band of vibration for isolated group B -O -V bridging bonds or V = O was located at 1000 cm -1 . The region from 511 -536 cm -1 was assigned to the in -plane bending of B -O and the IR band at around 740 -751 cm -1 was referred to the B -O -B bending vibration of BO4 and BO3 [5].
To evaluate the impact of vanadium on borate structure, the relative area of BO4 / V = O bands have been normalized by area of BO4 at x = 0 mol%. Addition of 0.5 mol% vanadium increased the relative area of BO3 functional group. However further addition of vanadium x > 0.5 mol% showed decreasing trend relative area BO3 functional group. The addition of 0.5 mol% V2O5 contents, decreased the normalized plot of BO4 / V = O but increased as increased the vanadium concentration into the glass samples. Increasing BO4 / V = O and decreasing BO3 indicates formation of NBO, whereas increasing BO3 and decreasing in normalize BO4 / V = O remarked increasing BO [19]. In this study, the NBO increased when the concentration of the vanadium x > 1.0 mol%. Figure 5 shows the absorption spectra for (59

UV-VIS Properties
5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%). The absorption spectra contain six bands placed at 490, 520, 540, 660, 800, and 980 nm. Comparing with other findings, all the peaks are referring the erbium absorption from the ground state 4 I15/2 to the excited states 4 F7/2, 2 H11/2, 4 S3/2, 4 F9/2, 4 19/2, and 4 111/2 respectively [24]. In comparison of peaks, the transition 4 I15/2 → 2 H11/2 with wavelength 520 nm has the highest peak. There are no new band was observed with addition of vanadium in the samples. It can be concluded, the bands due to vanadyl ion was not observed in recorded spectra or maybe overlap with erbium band. This is because to the dominance of erbium ion band intensity. The erbium ion intensity dominance, the SPR band contributed by silver nanoparticles also is not observed. There are many previous studies reported that the SPR band is expected to be around 400 -500 nm [25,26]. The SPR frequency is depending on the refractive index (n ̴ 2 for borate glass) and dielectric function of silver [27].

Optical Properties
The optical properties of amorphous material can be studied mainly regarding electronic band structure and optical transition. An electron in the valence band interacts with an electromagnetic wave, it has enough energy to rise across the bandgap to the conduction band. The energy required to cross the band gap closely related to the optical energy bandgap (Eopt).
The optical absorption edge is used to investigate the electronic transition during absorption. The absorption coefficient (α) can be calculated at various wavelength using the Beer-Lambert Law [5] Where I0, it is the incident and transmitted photon intensities. The samples thickness is t. By drawing a Tauc plot (figure 6) according Davis and Mott relation with α as follow [5]: Where h is plank constant v is the photon frequency, A is a constant, and n is a constant determining the types of transition. The n constant has different values of 2, 3, 1/2, or 1/3, which referring to indirect allowed, indirect forbidden, direct allowed, and direct forbidden transition, respectively [28]. The value of n for the oxide glass is 2 [5]. In this study, the graph hv against (αhv) 2 has been plotted ( Figure 6) and used to measure the optical band gap. The optical band gap is the intersection of the straight line of the curve at x-axis when the (αhv) 2 = 0 [24] hv (ev) The changes of band gap energy can be explained by the increase of decrease of disorder in the material. Using Urbach's equation, the disorder can be calculated [5].

(5)
Where α is a constant, and Eu is the urbach energy. The graph of ln (α) versus hv were plotted in Figure 7. The reciprocal of the slope of the linear to the curve referring to the urbach energy [5]. Urbach energy depended on several factors: temperature, average photon energy, induced disorder, static disorder, thermal vibration in the lattice, and strong ionic bond.  Table 2 shows the values of indirect energy band gap, Urbach energy, and refractive index of for all the samples. The energy band gap (Eopt) values in the range 3.143024 -1.752474 eV. Eopt decreased with increased vanadium concentration. The variation in Eopt and n against V2O5 concentration show contrasting behavior in figure 8, whereby n increased with increased vanadium concentration. This behavior has been showed for previous research [5]. The n values that lie in the range of 2.359592 -2.852138. In the studied glass samples, the reduction of band gap with increased V2O5 is due to structural evolution. For x < 1.0 mol%, the band gap decreases because increasing of NBO on borate triangular BO3 at low concentration of vanadium. The creation of NBO opened the glass structure and the electron easier to excited compared with the case in BO because the electron was loosely bond in NBO. The band gap most likely constant for x =1.5 mol% may be assumed to be due to the new role of V2O5 as former oxide. At low concentration, vanadium acts as network modifiers, while at high concentration, vanadium acts as network forming [11]. The structural revolution that happened with increasing vanadium concentration caused the contrasting behavior of n. Table 2. This is a table for indirect optical energy band gap (Eopt), Urbach energy (EU), and refractive index (n) of (59.5 -x) B2O3 -20Na2O -20CaO -xV2O5 -Er2O3 -0.5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%).  Figure 8. This is a figure for optical band gap (Eopt) and refractive index of (59.5 -x) B2O3 -20Na2O -20CaO -xV2O5 -Er2O3 -0.5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%).
The EU values of the glass increased sharply from 0.298338 -0.481603 eV (x = 0 -0.5 mol%), followed by a sharply decreased when 1.0 -1.5 mol% of vanadium added into the glass samples. The EU values gradual increased to 0.762137 (x = 2.5 mol%) with further increase in V2O5 content in Figure 9. The addition of vanadium x = 0.5 mol%, increase the Urbach energy value, which indicates the tendency of week bonds convert to defect increased. For x = 0.5 mol% the concentration of defect increased in the glass network with increased NBO. The Urbach energy value decreased for x = 1.0 and 1.5 mol%. This decrement suggests that, the degree of the disorder of the present glass decreased. However, for x > 1.5 mol% the Urbach energy increasing. The increase of Urbach energy impacted the decrease of energy band gap or decrease of Urbach energy, increase energy band gap.

Judd -Ofelt Analysis
Judd-Ofelt theory provides the information of transition behavior between 4f -4f electronic configuration and calculation of oscillation strength, intensity parameter (Ω2, Ω4, Ω6), transition probabilities, and branching ration [29,30]. The Judd -Ofelt theory is the best method to investigate and analyze the spectral properties of borate glass system containing rare earth ion (erbium ion). Absorption spectral data of all samples containing different concentration vanadium was used to calculate the Judd -Ofelt parameters. The precise integrated absorption cross section measurement over the range of wavelength and transition state of excitation is needed to analysis the Judd -Ofelt theory.
The area under the absorption band were used to determine the experimental oscillator strength. The experimental oscillator strength can be calculated via the relation: Where m is the electron mass, c is the velocity of light in vacuum, N0 is the Avogadro's number, and is the molar extinction coefficient. The molar extinction coefficient obtained from the measured absorbance of the samples which was calculated from the Beer-Lambert law as follow: Where is the concentration of the rare earth ion (erbium) (mol/1000 cm 3 ), t is the thickness of the samples in cm and last but not least is the calculated from absorbance at the wave-number v (cm -1 ).
The estimation of theoretical oscillator strength for a transition from the ground state to an excitation state of erbium ion within 4f configuration according to Judd-Ofelt theory as follow: Where v is the wavenumber of the transition in cm -1 , h is a plank constant, and J is the total angular momentum of the lowest state. The factor of (n 2 + 2)/9n represents for the electric field correction of Lorentz, and n is the refractive index of the samples. Ωλ is Judd -Ofelt intensity parameter where are 2,4, and 6.
represents the double-reduced square matrix elements of the unit tensor operator of rank = 2,4, and 6 are calculated using the intermediate coupling approximation method for transition lowest state to highest states. The reduce matrix elements are calculated following Carnall et al [31].
To evaluate the accuracy of the Judd -Ofelt parameter, the quality of the fit was identified by the root-mean-square (rms) deviation relation: (10) Where is three, the number of spectral bands analyzed. The values of rms indicates the quality of the fit between experimental oscillator strength and calculated oscillator strength. These values also show the accuracy of the Judd -Ofelt parameter. Table 3 shows the rms and oscillator strength for calculated and experimental of all the glass samples. Indirect data on the symmetry and bonding of rare earth ions within the matrix was provided by oscillator strength. The highest oscillator force attributed to the hyper-sensitive transition was shown by the transition band at 4 I15/2 → 2 H11/2. Such hyper-sensitive transitions are sensitive to changes in the local structure of the glass network. These hyper -sensitive transition comply with the ∆S = 0, |∆J| 2 and |∆L| 2 selection rules and reflects the interaction strength of erbium ions in the local network with host glass. In the present glass samples, with the increase in vanadium content, increases in the oscillator strength of hyper -sensitive transition. These changes reveal strong covalency with the presence of lower symmetry around erbium ions. These values are found have highest oscillator strength comparing with phosphate glass [14,32], boroaluminosilicate glass [10] and tellurite glass [16,26]. In addition, the values of rms are in the range 1 -2 × 10. These very small rms value confirmed the accuracy of the data [33].
The rms values of all the glass samples are good agreement when compared with previous study [34]. Table 3. This is a table for calculated oscillator strength (fcal, 10 -6 ), the experimental oscillator strength (fexp, 10 -6 ) and rms of the erbium absorption transition from the ground state 4 I15/2 to the excited states.

Transition 4 I15/2→
Glass samples x = 0 mol% x = 0.5 mol% x = 1.0 mol% x = 1.5 mol%  Table 4 shows the values of Judd -Ofelt intensity parameters (Ω2, 4,6) and their spectroscopic properties (χ) along with trend of Judd -Oflet parameter for all the glass samples. The data of Judd -Ofelt parameter from previous reported literature will be utilized for comparison with current glass samples [34]. The composition of the glass determines the values of Judd -Ofelt parametes. The increasing in vanadium ions concentration from 0 to 1.0 mol% impact to decrease Ω2 and Ω6 values from 3.19×10 -20 to 2.43×10 -20 and 8.45×10 -21 to 6.53×10 -21 , respectively. In addition, it can be seen the trend of Ω was found to Ω2 > Ω4 > Ω6 for all the glass prepared samples. The samples with Ω2 and Ω4 higher intensity parameters compared with Ω6 can be regarded as the good glass host because have high luminescence intensity ratio and high covalent bond between erbium ion and local environment ligand [34,35]. The values of Ω2 and Ω4 was smaller for borate glass containing erbium ion co -doped vanadium compared to borate glass containing erbium ion only [34]. The parameters Ω2 and Ω4 are highly sensitive to the rare earth ion's local environment symmetry. The small values of Ω2 and Ω4 indicates the lower asymmetric nature of the local environment around erbium ion exists in the glass system [37].
The Ω6 contradict to the Ω2 and Ω4, where Ω6 does not depend on the local structure [38] and normally the rigidity of the glass correlated to these parameter [34]. The glass without vanadium concentration (x = 0) more rigid compare to others glass samples (x = 0.5 -2.5 mol%). Since the value of Ω6 for glass without vanadium is bigger than other samples (with vanadium). The addition of vanadium ions concentration from 0 to 1.0 mol% leads to decrease Ω6 values from 8.45×10 -21 to 6.53×10 -21 . This is because of NBO was created around the host matric. The creation of NBO causes high number of covalency and lead to produce high number of electron density of the ligand ions.
The values of Ω4 and Ω6 parameters was used to determine the spectroscopic quality factor (χ) [39]. The χ will define the efficiency of laser transition. Therefore, it can be used to predict the stimulated emission of the laser. The values of χ for all the glass samples in the range of 1.70781 -1.95143. These values were bigger than erbium in tellurite glass system [24]. The bigger the value of χ reveals the higher efficiency of laser transition because according to [40] report that, the higher the value of χ, the more intense of the laser transition. In this study, the glass with 1.0 mol% of vanadium shows to be optically better compared to others glass samples. The values of Ωλ were used to calculate the radiative properties such as spontaneous emission rate (AR), branching ratio (βR), and lifetime of the radiative transition (τrad). The emission probabilities probabilities and called as Einstein coefficient for radiative transition AR (aJ, bJ') of the different transition are calculated by, Where Aed and Amd stand for electric dipole and magnetic dipole respectively and both are calculated using equation (9) and (10) respectively: and is for the local -field correction for electric dipole and magnetic dipole transition, respectively. Both are obtained by using the ralations: The line-strength for magnetic dipole and electric dipole transition represented by , , respectively. Both are given by the relations: From the table 5, the 4 I15/2 → 2 H11/2 and 4 I15/2 → 4 F7/2 transition have high values for AR. In addition, these 2 H11/2 and 4 F7/2 increase in AR values when concentration of vanadium increase in the glass samples. It indicates the transition of 2 H11/2 and 4 F7/2 are beneficial to green and blue emission suitable for laser, respectively [38].
In addition, the radiative lifetime is very important data for laser and optical amplifier. The radiative lifetime (τrad) of prepared glass is a reciprocal of the total transition probabilities of an emission state (sum of transition probabilities of all the transition from highest state to various lower states): (18) Lastly, the emission branching ratio are given by relations, The obtained values of τ and R are listed in table  5. The probability of simulated emission acquisition can be determined by the values of branching ratio for a specific transition [42]42]. The values or branching ration for transition of 4 I15/2 → 2 H11/2 and 4 I15/2 → 4 F7/2 is 99 % and the value of radiative ratio in the range 0.007151 -0.004662. the value of the present glass is shorter compared to other glass system. The shorter radiative lifetime of this transition was beneficial for the control of the strong emission of erbium ion within the prepared glass system and the suppression of the non-radiative process. Table 5. This is a table for values of AR (s -1 ), βR (%), and τ (ms) of all prepared glass samples.

Trans.
Para. x = 0 mol% x = 0.5 mol% x = 1.0 mol% x = 1. 5 Figure 10 reveals the photoluminescence (PL) emission spectra of the (59.5 -x) B2O3-20Na2O-20CaO -xV2O5 -Er2O3 -0.5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) glass samples in the wavelength range 400 -800 nm. The excitation wavelength was 800 nm. The emission spectra of Er 3+ ions exhibited three dominant peaks at 516 nm, 580 nm, and 673 nm. These peaks were assigned to 2 H11/2 -4 I15/2, 4 S3/2 -4 I15/2, and 4 F15/2 -4 I15/2. The band at 516 nm, 580 nm, and 673 nm due to stark splitting effects. The stark splitting effect because of low symmetry of the local environment around erbium ion [44]. The intensity increases when the concentration of V2O5 increases from 0 mol% to 1.5 mol%. However, when the concentration of vanadium more than 1.5 mol%, the intensity decreases. Thus, the decrement was due to a concentration quenching [44,45]. It is suggested that, at a higher amount of vanadium, the excess vanadium ions produce structural defects that cause non-radiative recombination process. The transition from excited state to the visible wavelength can be ascribed by the emission of peaks at 516nm, 580nm, and 673nm [44].   Figure 10. This is a figure of emission spectra of all the glass samples with excitation wavelength at 800 nm.

Conclusions
The effect of V2O5 substitution on structural and optical properties (59.5 -x) B2O3 -20Na2O -20CaO -xV2O5 -Er2O3 -0.5AgCl (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) glasses were investigated. The glass had been successfully prepared via the melt-quenching method. The structural of the samples by XRD has indicated the glasses have amorphous nature without any crystalline phase when addition of vanadium. Meanwhile, the FTIR revealed the structural units in the glasses network. Thus, the FTIR confirmed the presence of B-O-B starching in borate network, bending vibration from the V -O -V of the VO4 tetrahedral group, vibration of the B -O -V bridging bond, and stretching vibration B -O bond belong to BO3. Addition of vanadium more or equal to 1.0 mol% create more NBO in the glass structural. Vis-NIR spectra exhibit eight absorption band which are 490, 520, 540, 660, 800, and 980 nm. All the peaks are referring the erbium absorption from the ground state 4 I15/2 to the excited states 4 F7/2, 2 H11/2, 4 S3/2, 4 F9/2, 4 19/2, and 4 111/2 respectively and the most intense peak centered at 540 nm and called as hypersensitive transition. The SPR band and vanadium band does not observe in the recorded spectra due to low concentration of silver nanoparticle and dominance of erbium band. The increase in vanadium is found to reduce band gap energy and increase the refractive index and Urbach energy from 2.359592 to 2.852138 and 0.298338 eV to 0.762137 eV. According to Judd -Ofelt principle, the spectroscopic parameter was calculated such as Judd -Ofelt parameter, quality factor, radiative lifetime, and branching ratio. The Judd -Oflet parameter was revealed to follow the trend Ω2 > Ω4 > Ω6. The photoluminescence spectra exhibit three band at 516 nm, 580 nm, and 673 nm which are represented by 2 H11/2 -4 I15/2, 4 S3/2 -4 I15/2, and 4 F15/2 -4 I15/2, respectively. The obtained results of Judd -Ofelt and photoluminescence shows the glass samples with 1.0 mol% of vanadium is very useful in green laser application since have high values of lifetime, branching ratio and strong spectral intensity compare to other samples.

Patents
Author Contributions: N.A.Z and S.N.M completed the data collection. N.A.Z as a first author drafted the first manuscript. Z.M revised the manuscript and have approved the final of the manuscript for publication.