K Annapurna

Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3-GeO2-ZnO glasses.

In this work, a new and non-conventional oxide glass composition based on Bi2O3-GeO2-ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho(3+)/Yb(3+) for the energy transfer based NIR emission at 2 μm from Ho(3+) ions under Yb(3+) excitation. The glass with 1.0 mol% Ho2O3 and 0.5 mol% Yb2O3 has exhibited maximum energy transfer rate (3602 s(-1)) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho(3+) ions using intensity parameters derived from measured absorption spectra using standard Judd-Ofelt theory. At lower acceptor ion concentration (0.1 mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho(3+) concentrations with simultaneous enhancement in 2 μm emission. Hence, this newly developed glass codoped with Yb(3+)/Ho(3+) is promising glass for sensitized 2 μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707 cm(-1)), high energy transfer efficiency, moderately high emission cross-section (5.33×10(-21) cm(2)) and larger effective half-width of the emission band value of 169 nm.

Temperature dependent luminescence characteristics of Sm3+-doped silicate glass

Abstract We report here on the optical characterisation of Sm 3+ (5 wt%): SiO 2 +Al 2 O 3 +Li 2 O+Na 2 O+MgO glass from the measurements of optical absorption spectra (at 300 K), total luminescence spectra (10–300 K) and fluorescence lifetimes (10–300 K) of the prominent emission transitions of the Sm 3+ ions. Besides its spectral properties, physical and nonlinearity characterising property parameters have also been computed to understand the optical dispersive power of this glass. By the application of Judd–Ofelt parameters ( Ω λ ) of the measured absorption spectrum, the radiative transition probability factors ( A ) and stimulated emission cross-section ( σ E p ) of the observed fluorescent levels have been analysed. Both emission intensity and measured lifetimes of the prominent luminescent transition ( 4 G 5/2 → 6 H 7/2 ) concerning Sm 3+ -glass has been showing a descending trend with the rise in temperature with N 2 -laser (337.1 nm) as the source of excitation.

Spectral analysis of Ho3+: TeO2–B2O3–Li2O glass

Abstract A highly transparent and little yellow-coloured Ho 3+ doped TeO 2 –B 2 O 3 –Li 2 O glass was prepared in order to study its optical properties from the measured UV–VIS–NIR absorption, emission and up-conversion emission spectra. We observed a prominent and bright red colour when this optical glass was brought under a UV lamp. The recorded up-conversion emissions revealed a strong green colour along with blue and violet colours upon excitation with λ exc =643 nm, and the mechanism was explained by an energy level diagram as a three photon absorption process.

Study on Tb3+ containing high silica and low silica calcium aluminate glasses: Impact of optical basicity

Two series of glasses based on high silica (CAS) and low silica calcium aluminates (LSCA) have been investigated for their structural, optical and Tb(3+) luminescence properties. The compositional modification reduces host phonon energy in LSCA glasses. Still, LSCA glasses exhibit Tb(3+) green luminescence quenching, whereas no quenching observed in CAS glasses. Material property influence on this behaviour has been discussed with an insight into the redox state of active ions.

Broadband Er 3+ emission in highly nonlinear Bismuth modified Zinc-Borate glasses

Broadband NIR emission from Er3+ in highly nonlinear zinc-bismuth-borate glasses with full width at half maximum reaching up to 106 nm is reported. The glass compositional effects on thermal, structural, optical and spectroscopic properties have been explored in view of all-optical communication applications. The Zero Dispersion Wavelength of these glasses is found to be varying from 1.46 to 2.26μm. The observed enhancement in fluorescence intensity, lifetime and quantum efficiency of 4I13/2 → 4I15/2 transition with bismuth addition is attributed to reduced multiphonon relaxations with decreased host phonon energy. The gain profile covering C and L-bands of communication windows suggests their potentiality in broad-band amplification.

Fluorescence spectra of Cu+: ZnO-B2O3-SiO2 glass

Abstract This short paper brings out an analysis on the fluorescence spectral properties of Cu + ions in a zinc borosilicate glass. A strong emission peak at 500 nm has been observed upon excitation with 296, 310 and 360 nm based on the measured excitation spectrum of this phosphorescent copper glass. This greenish blue broader luminescent transition has been due to a spin forbidden transition ( 3 E g → 1 A g ) showing significant changes in its lifetime (ms) values depending upon the excitation wavelength used.

Yb 3+ ion concentration effects on ∼1 μm emission in tellurite glass

The effects of Yb3+ ion concentration on physical, optical, and spectroscopic properties have been studied in a low phonon (∼590  cm−1) barium-lanthanum-tellurite glass. Due to the unfeasibility of Judd-Ofelt theory Yb3+-doped systems, the oscillator strength of absorption transition, F27/2→F5/22 has been evaluated by using the Smakula equation. The nature of emission from F25/2→F7/22 transition of Yb3+ ions is described theoretically by using a rate equation in comparison with experimental results. By applying reciprocity (RM) and Fuchtbauer-Ladenburg methods on emission spectra as well as the excitation random walk model on measured fluorescence lifetimes, the radiation trapping and concentration quenching effects have been discussed. Considering all the spectroscopic and laser performance parameters, an optimum Yb-ion doping concentration (YT1) has been determined, and the gain measurements performed on the sample revealed a flat gain over a broad wavelength range could be achieved even with a low (∼20%) excitation population density. A comparative study with other hosts revealed the potentiality of the present glass for ∼1 micron emission.

NIR emission and upconversion luminescence spectra of Nd3+:ZnO–SiO2–B2O3 glass

Abstract Zinc-borosilicate glass containing Nd 3+ ions has been prepared to study the NIR fluorescence and the violet upconversion emission properties. NIR photoluminescence spectrum has been recorded with the 514-nm line of Ar + laser and observed three emission transitions of 4 F 3/2 → 4 I 13/2,11/2, 9/2 . The decay curve of the prominent lasing transition 4 F 3/2 → 4 I 11/2 has been measured both at 514-nm line of an Ar + laser and at 808 nm of a pulsed laser diode. A bright violet color upconversion emission has been measured from a yellow light ( 4 I 15/2 → 4 G 5/2 at 576 nm) of a xenon arc lamp.

Energy transfer kinetics in oxy-fluoride glass and glass-ceramics doped with rare-earth ions

An investigation of donor-acceptor energy transfer kinetics in dual rare earths doped precursor oxy-fluoride glass and its glass-ceramics containing NaYF4 nano-crystals is reported here, using three different donor-acceptor ion combinations such as Nd-Yb, Yb-Dy, and Nd-Dy. The precipitation of NaYF4 nano-crystals in host glass matrix under controlled post heat treatment of precursor oxy-fluoride glasses has been confirmed from XRD, FESEM, and transmission electron microscope (TEM) analysis. Further, the incorporation of dopant ions inside fluoride nano-crystals has been established through optical absorption and TEM-EDX analysis. The noticed decreasing trend in donor to acceptor energy transfer efficiency from precursor glass to glass-ceramics in all three combinations have been explained based on the structural rearrangements that occurred during the heat treatment process. The reduced coupling phonon energy for the dopant ions due to fluoride environment and its influence on the overall phonon assisted ...

Emission properties of Eu3+ ions in ZnCl2-BaCl2-KCl glass

Abstract In this short communication, we present the results concerning the excitation and emission spectra of 1 mol% Eu 3+ -doped 50ZnCl 2 +20BaCl 2 +29KCl glass. A bright red color emission was observed under an UV source from this glass. The photoluminescence spectra have shown prominent red emission transition ( 5 D 0 → 7 F 2 ) at 610 nm along with three other weak emission transitions of 5 D 0 → 7 F 0, 1 and 3 at 580, 598 and 650 nm upon excitation with six identified excitation bands. Dependence of the emission intensities and lifetimes based on the excitation wavelengths employed has been investigated.