Y.C. Ratnakaram

Investigations on luminescence performance of Sm3+ ions activated in multi-component fluoro-phosphate glasses.

Different metal oxide based fluoro-phosphate glasses doped with Sm(3+) ions are investigated using XRD, SEM with EDS, FTIR, Raman spectra, optical absorption and photo-luminescence techniques. These glass matrices have been prepared by conventional melt quenching technique. The glassy nature of the present glass matrices are confirmed by XRD profiles and SEM photographs. The composition of the glasses is checked by EDS. Based on FTIR and Raman spectra, the authors have analyzed functional groups that are present in the glass matrices. Judd-Ofelt intensity parameters, Ωλ (λ=2,4,6) have been evaluated from absorption spectra. Radiative parameters such as radiative transition probabilities (AR), radiative lifetimes (τR), integrated absorption cross sections (Σ) and branching ratios (βR) are calculated using Judd-Ofelt intensity parameters. From the photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) for all the observed emission transitions are calculated. To investigate luminescence potentiality of (4)G5/2→(6)H7/2 emission level of Sm(3+) doped different fluorophosphate glasses, experimental radiative lifetimes (τexp) are obtained from decay curve analysis for all glass matrices. Finally, these observed results are discussed and compared with the literature data.

Spectroscopic investigations on Pr3+ and Nd3+ doped strontium–lithium–bismuth borate glasses

Spectroscopic investigations on different concentrations (0.1, 0.5, 1.0, 1.5 and 2.0mol%) of Pr(3+) and Nd(3+) doped strontium lithium bismuth borate glasses have been done. X-ray diffraction, SEM with EDS, absorption and luminescence spectra were recorded for all the glass matrices and analyzed. X-ray diffraction profiles and SEM images conformed amorphous nature of investigated glass samples. EDS spectra of host glass and Pr(3+)doped glass matrices gave information about the chemical composition of glass samples. From the absorption spectra of Pr(3+) and Nd(3+) ions, Judd-Ofelt (J-O) intensity parameters (Ω(λ),λ=2, 4 and 6) have been calculated and compared with other glass matrices. The emission characteristics such as radiative lifetimes (τ(R)), measured and calculated branching ratios (β) and stimulated emission cross-sections (σ(P)) have been obtained for the observed emission transitions of Pr(3+) and Nd(3+) ions in the above glass matrix for all the concentrations. From the emission spectra of Pr(3+) and Nd(3+) doped glass matrices, the effect of concentration on the quenching of intensity of (1)D(2)→(3)H(4) transition of Pr(3+) ion and (4)F(3/2)→(4)I(9/2), (4)I(11/2) and (4)I(13/2) transitions of Nd(3+) have been studied and discussed.

Spectroscopic investigations of Er3+ in H3BO3Na2CO3RCl glasses

Abstract The optical properties of Er3+ doped 80H3BO310Na2CO310RCl (RNa, K, Li, Zn and Pb) glasses have been measured. From the optical absorption measurements and using Judd-Ofelt theory, the Judd-Ofelt parameters, Ω 2 , Ω 4 and Ω 6 , have been calculated. Measured oscillator strengths (fmeas) for various energy levels are compared with calculated values (fcal) and are in reasonable agreement. The position of the absorption edge and hence the values of optical band gaps are reported for five compositions. The predicted radiative transition probabilities (A), radiative lifetimes (τR), branching ratios (β) and integrated absorption cross sections (Σ) for the excited states 4G 11 2 , 4F 5 2 , 4F 7 2 , 4S 3 2 , 4F 9 2 , 4I 9 2 , 4I 11 2 and 4I 13 2 of Er3+ in different chloroborate glasses are reported.

Optical properties and spectroscopic study of different modifier based Pr3 +:LiFB glasses as optical amplifiers

In this paper, we report the preparation and optical characterization of Pr(3+) doped lithium fluoro borate (LiFB) glasses for six different chemical compositions of Li2B4O7-BaF2-NaF-MO (where M=Mg, Ca, Cd and Pb), Li2B4O7-BaF2-NaF-MgO-CaO and Li2B4O7-BaF2-NaF-CdO-PbO. The structural and optical properties of these glasses were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), optical absorption and photoluminescence techniques. The optical absorption spectra of Pr(3+) ions in LiFB glasses have been recorded in the UV-VIS-NIR region. The optical absorption data are used to calculate various spectroscopic parameters such as Racah (E(1), E(2), E(3)) and spin-orbit interaction (ξ4f) parameters. Judd-Ofelt (J-O) (Ωλ where λ=2, 4 and 6) intensity parameters were determined by applying J-O theory, which in turn used to calculate the radiative properties such as radiative transition probabilities (A), radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βr) for all emission levels of Pr(3+) ion in different LiFB glass matrices. By using the J-O theory and luminescence parameters, stimulated emission cross sections (σp) of prominent transitions, (3)P0→(3)H4 and (1)D2→(3)H4 of Pr(3+) ion in all LiFB glasses were calculated. (3)P0→(3)H4 possesses higher branching ratios and stimulated emission cross-sections for the Pr(3+):LiFB(Mg-Ca) glass, which can be used as a best laser excitation. The optical gain parameter (σpxτR) was noticed higher in Pr(3+):LiFB(Mg-Ca) and Pr(3+):LiFB(Cd-Pb) glasses for the transition (3)P0→(3)H4 transition, and these glasses have potential for optical amplification at 488 nm wavelength.

Luminescence performance of Eu3+-doped lead-free zinc phosphate glasses for red emission

In this study, the luminescence performance of zinc phosphate glasses containing Eu3+ ion with the chemical compositions (60–x)NH4H2PO4-20ZnO-10BaF2-10NaF–x Eu2O3 (where x = 0.2, 0.5, 1.0 and 1.5 mol%) has been studied. These glasses were characterized by several spectroscopic techniques at room temperature. All the glasses showed relatively broad fluorescence excitation and luminescence spectra. Luminescence spectra of these glasses exhibit characteristic emission of Eu3+ ion with an intense and most prominent red emission (614 nm), which is attributed to 5D0 → 7F2 transition. Judd-Ofelt (Ω2, Ω4) parameters have been evaluated from the luminescence intensity ratios of 5D0 → 7FJ (where J = 2 and 4) to 5D0 → 7F1 transition. Using J-O parameters and excitation spectra, the radiative parameters are calculated for different Eu3+-doped glasses. Effect of γ-irradiation at fixed dose has been studied for all the Eu3+-doped glass matrices. The lifetimes of the excited level, 5D0, have been measured experimentally through decay profiles. The colour chromaticity coordinates are calculated and represented in the chromaticity diagram for Eu3+-doped zinc phosphate glasses for all concentrations.

Bright green emission from f-MWCNT embedded co-doped Bi3+ + Tb3+:polyvinyl alcohol polymer nanocomposites for photonic applications

A bright, dazzling green emission has been obtained from functionalized multi walled carbon nanotube (f-MWCNTs)-embedded Bi3+ + Tb3+:PVA polymer nanocomposites under UV excitation. We successfully synthesized Tb3+:PVA, Bi3+ + Tb3+:PVA and Bi3+ + Tb3+ + f-MWCNTs:PVA polymer films by a solution casting method. For these polymer films, their XRD and FTIR spectral profiles were analyzed for structural details and ion–polymer interaction mechanism. Tb3+ doped at different concentrations in PVA polymer films displayed a green emission at 546 nm (5D4 → 7F5) under 370 nm (7F6 → 5L10) excitation. Upon co-doping with Bi3+ in the Tb3+:PVA polymer film, the film exhibits enriched green emission compared to single Tb3+:PVA under 320 nm excitation due to the energy transfer from Bi3+ to Tb3+. Surprisingly, a common excitation band was found at 320 nm for Tb3+, Bi3+ and f-MWCNTs. After dispersion of the f-MWCNTs in the co-doped Bi3++Tb3+:PVA polymer films, the photoluminescence properties were remarkably enhanced, and a prominent green emission was observed at 546 nm. The green emission of Tb3+ is significantly enhanced though an efficient energy transfer process from Bi3+ to Tb3+ and f-MWCNTs to Tb3+. The possible energy transfer mechanism was clearly demonstrated via several fluorescent methods. The energy transfer mechanism was substantiated with fluorescence lifetime decay dynamics. From these results, these f-MWCNTs-embedded Bi3++Tb3+:PVA polymer films could be suggested as promising candidates for green luminescent materials for photonic devices.

Impact of Bi2O3 on structural properties and lasing effects in Nd3 + doped bismuth phosphate glasses at 1.053 μm emission

Influence of addition of bismuth oxide (Bi2O3) on structural and optical properties of 0.5Nd3+doped different phosphate glasses prepared by melt quenching technique were reported. The structural properties were analysed by FT-IR and 31P MAS NMR techniques. 31P NMR results showed that, with the variation of Bi2O3 concentration in the prepared phosphate glass matrices there was no significant change in the structure. The optical properties have been analysed using Judd-Ofelt (J-O) theory. From absorption spectra, three phenomenological J-O intensity parameters (Ω2, Ω4, Ω6) have been calculated and these parameters were used to estimate the radiative properties. The J-O intensity parameters increased with increase in the concentration of Bi2O3, which confirmed the higher covalency, asymmetry and rigidity. The branching ratios (β) and emission cross-sections (σ) were calculated from the emission spectra of Nd3+ doped bismuth phosphate (BiP) glasses. Among different glass matrices 15mol% of Bi2O3 glass matrix has higher β and σ values which are useful for the laser applications. The improved emission cross-section value with the addition of Bi2O3 content results low threshold and high gain applications. The decay curves of all these BiP glasses showed single exponential behaviour.

NIR emission at 1.53 μm in Er3+ doped lead free zinc phosphate glasses for potential broadband optical amplifiers

Er3+ doped zinc phosphate glasses with chemical compositions (60-x) NH4H2PO4 + 20ZnO+10BaF2+10NaF+xRE (where RE=Er2O3, x = 0.1, 0.5, 1.0, 1.5 and 2.0 mol%) have been prepared by melt quenching technique. Amorphous structure was ascertained by XRD analysis. The functional bands have been assigned and clearly elucidated by FT-IR spectral profiles for host glass sample. Judd-Ofelt (J-O) intensity parameters (Ωλ: λ=2, 4, 6) have been obtained from the spectral intensities of different absorption bands of Er3+ ion through optical absorption spectra. NIR photoluminescence spectra exhibited one emission band (4I15/2→4I13/2) of Er3+ ions. These glasses were suggested as suitable hosts for efficient lasing action in NIR region at 1534 nm for Er3+ ion.

Structural, optical and luminescence properties of Dy3+ doped bismuth phosphate glasses: Insights from 31P MAS NMR, absorption and photoluminescence

An investigation was carried out to observe structural and optical properties of 0.5 mol% Dy3+ doped different compositions of bismuth phosphate glasses (5, 10, 15 and 20 mol% Bi2O3). The structural characterization was accomplished by X-ray diffraction (XRD), 31P magic angle spin nuclear magnetic resonance (MAS NMR) spectroscopy. The optical properties were studied using absorption and photo luminescence (PL) spectroscopy. Judd-Ofelt intensity parameters Ωλ (λ=2, 4 and 6) were evaluated from absorption spectra. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated. The decay profiles for 4F9/2 level were recorded and were fit exponential. The obtained results show the prepared Dy3+ doped bismuth phosphate glasses might be useful as good optical material for yellow emission.An investigation was carried out to observe structural and optical properties of 0.5 mol% Dy3+ doped different compositions of bismuth phosphate glasses (5, 10, 15 and 20 mol% Bi2O3). The structural characterization was accomplished by X-ray diffraction (XRD), 31P magic angle spin nuclear magnetic resonance (MAS NMR) spectroscopy. The optical properties were studied using absorption and photo luminescence (PL) spectroscopy. Judd-Ofelt intensity parameters Ωλ (λ=2, 4 and 6) were evaluated from absorption spectra. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated. The decay profiles for 4F9/2 level were recorded and were fit exponential. The obtained results show the prepared Dy3+ doped bismuth phosphate glasses might be useful as good optical material for yellow emission.

Luminescence performance of Eu3+ doped lead free zinc phosphate glasses for red emission

In this study, the luminescence performance of zinc phosphate glasses containing Eu3+ ion with the chemical compositions (60–x)NH4H2PO4-20ZnO-10BaF2-10NaF–x Eu2O3 (where x = 0.2, 0.5, 1.0 and 1.5 mol%) has been studied. These glasses were characterized by several spectroscopic techniques at room temperature. All the glasses showed relatively broad fluorescence excitation and luminescence spectra. Luminescence spectra of these glasses exhibit characteristic emission of Eu3+ ion with an intense and most prominent red emission (614 nm), which is attributed to 5D0 → 7F2 transition. Judd-Ofelt (Ω2, Ω4) parameters have been evaluated from the luminescence intensity ratios of 5D0 → 7FJ (where J = 2 and 4) to 5D0 → 7F1 transition. Using J-O parameters and excitation spectra, the radiative parameters are calculated for different Eu3+-doped glasses. Effect of γ-irradiation at fixed dose has been studied for all the Eu3+-doped glass matrices. The lifetimes of the excited level, 5D0, have been measured experimentally through decay profiles. The colour chromaticity coordinates are calculated and represented in the chromaticity diagram for Eu3+-doped zinc phosphate glasses for all concentrations.