Doped Fluorophosphate Glasses Research Articles

Spectral and laser properties of Yb3+ doped aluminium fluorophosphate glasses

Spectral and laser properties of Yb3+ doped aluminium fluorophosphate glasses

Optical spectroscopy and frequency upconversion properties of Tm3+ doped tungstate fluorophosphate glasses

Tungstate fluorophosphate glasses of good optical quality were synthesized by fusion of the components and casting under air atmosphere. The absorption spectra from near-infrared to visible were obtained and the Judd–Ofelt parameters determined from the absorption bands. Transition probabilities, excited state lifetimes and transition branching ratios were determined from the measurements. Pumping with a 354.7 nm beam from a pulsed laser resulted in emission at 450 nm due to transition D21→F43 in Tm3+ ions and a broadband emission centered at ≈550 nm attributed to the glass matrix. When pumping at 650 nm, two emission bands at 450 nm (1D2→3F4) and at 790 nm (3H4→3H6) were observed. Excitation spectra were also obtained in order to understand the origin of both emissions. Theoretical and experimental lifetimes were determined and the results were explained in terms of multiphonon relaxation.

Enhancement of optical properties of Nd3+ doped fluorophosphate glasses by alkali and alkaline earth metal co-doping

Fluorophosphate glasses doped with trivalent Nd and using Li and Ba as network modifier cations are spectroscopically analyzed to understand the effects of these cations on the radiative and non-radiative process. The radiative properties of Nd3+ such as radiative transition probabilities, radiative decay times and stimulated emission cross-sections of the transitions from the 4F3/2 level, and their dependence on network modifiers and active ion concentration are analyzed using the Judd–Ofelt theory. Results show that, eventhough stimulated emission cross-section is maximum in Li based glass, fluorescence quenching is higher, however it is considerably reduced by the presence of Ba. It is found that, Ba and LiBa based glasses yield higher quantum efficiency showing that Ba reduces the fluorescence quenching properties of the matrix. The stimulated emission cross-section of the emission band at 1.055 μm is higher than that of commercial laser glasses. On the other hand, quantitative estimation of the non-radiative processes such as multiphonon relaxation and quenching by water content shows that water content is far below the critical level of optimum laser performance. All these factors pertain to the fact that these Nd3+ doped fluorophosphate glasses can be effectively used for high power lasers in the 0.8 and 1.055 μm regions.

Energy transfer and frequency upconversion in Pr 3+-doped fluorophosphate glass

We have investigated the process of fluorescence quenching from the 1D 2 state of Pr 3+ ions in fluorophosphate glasses of composition 60NaPO 3–15BaF 2–(25 − x)GdF 3– xPrF 3 ( x=0.1, 0.2, 0.5, 1, 2, 5, and 10) (in mol%) due to energy transfer among Pr 3+ ions. The fluorescence of the 1D 2 level is concentration quenched for Pr 3+ concentrations >0.1 mol% even at 4.2 K. The non-exponential dependence of the decay from the 1D 2 level with increasing concentration, together with the dependence of the effective decay rates on Pr 3+ concentration, indicates the presence of a dipole–dipole quenching process in the framework of a limited diffusion regime. Anti-Stokes emission from the 3P 0 level following excitation of the 1D 2 state is also observed. This anti-Stokes emission is attributed to upconversion by energy transfer.

Spectroscopic properties of Pr3+ ions in fluorophosphate glass

The visible luminescence of Pr3+-doped fluorophosphate glasses of composition (in mol%) 60NaPO3–15BaF2–(25 − x)GdF3–xPrF3 (x=0.1, 0.2, 0.5, 1, 2, 5, and 10) has been investigated as a function of concentration at different temperatures by using steady-state and time-resolved laser spectroscopy. The fluorescence of the 1D2 level shows a strong concentration quenching for Pr3+ concentrations higher than x=0.1 mol% even at 4.2 K. The non-exponential character of the decays of the 1D2 level when increasing concentration, together with the behaviour of the effective decay rates as a function of Pr3+ concentration, indicate the presence of a dipole–dipole quenching process in the framework of a limited diffusion regime.

Optical properties of -doped fluorophosphate glasses

Optical absorption spectra of the -doped fluorophosphate glasses 75 (A = Mg, Ca, Ba, Zn), 75 and 58 have been recorded. The dipole strengths are parametrized in terms of three phenomenological Judd-Ofelt intensity parameters (, 4 and 6). With the knowledge of these intensity parameters, the probability for spontaneous emission, the branching ratios and the radiative lifetime are calculated. The relation between the spectral intensities and the glass composition is discussed.

Optical properties of Nd3+-doped fluorophosphate glasses

Optical absorption spectra of Nd3+-doped fluorophosphate glasses of the type 75NaPO3–24AF–1NdF3 (A=Li, Na, K) and of the type 75NaPO3–24AF2–1NdF3 (A=Ca, Sr, Ba, Zn, Cd) have been recorded. The dipole strengths are parameterised in terms of three phenomenological Judd–Ofelt intensity parameters Ωλ (λ=2, 4 and 6). With the knowledge of these intensity parameters, the probability for spontaneous emission, the branching ratios and the radiative lifetime are calculated. The relation between the spectral intensities and the glass composition is discussed. The optical properties of the fluorophosphate glasses are compared with those of phosphate and fluoride glasses. It is shown that the choice of the cation only has a minor influence on the spectral intensities. The spectral behaviour of the fluorophosphate glasses is intermediate between the spectral behaviour of pure phosphate and fluoride glasses.

Er3+-doped fluorophosphate glass fibre amplifier for WDM systems

An Er/sup 3+/-doped fluorophosphate glass fibre amplifier has been constructed for the first time. Its fundamental gain and noise characteristics have been characterised. This amplifier can amplify an 8 channel WDM signal in the 1532-1560 nm wavelength region with a gain non-uniformity of 1.1 dB. In this case, the average signal gain and the noise figure of the fibre are 8.2 dB and <6 dB, respectively.

Excited state absorption mechanisms of red to UV and blue conversion luminescence in Tm 3+ doped fluorophosphate glass

Characteristics and ion-ion interaction processes important in the optical dynamics of UV and blue upconversion luminescence in Tm 3+ doped fluorophosphate glass have been investigated by exciting Tm 3+ ions into the 3F 2 level with a DCM dye laser tuned at 657 nm. Two emission bands centered at 363, 451 nm from the 1D 2 level and one emission band centered at 478 nm from the 1G 4 level were observed. The 451 nm emission was stronger than the 478 nm emission. The excitation power dependence of all the upconverted emissions were found to be quadratic, conforming the two photon nature of these transitions. The mechanism leading to these emissions was attributed to the excited state absorption (ESA) from the 3F 4 and 3H 4 levels for the emissions of the 1D 2 and 1G 4 levels, respectively. The loss mechanism due to ion-ion interaction in the 3F 4 level therefore was studied as function of temperature by measuring the spectral overlap between emission and absorption spectra of this level. From this data relevant microscopic interaction parameters that give a measure of Tm-Tm coupling have been calculated. Optical properties of the intermediate and the final levels involved in the upconversion processes were studied using the Judd-Ofelt theory. This theory was also used to determine radiative transition rates and the fluorescence quantum efficiencies of the excited levels, and the excited state absorption coefficient for the 3F 4 → 1D 2 and 3H 4 → 1G 4 transitions when the excitation was fixed at 657 nm. Lower excited state absorption coefficient of the former transition explains why the 478 nm emission intensity is weaker than 451 nm emission intensity in this glass. According to the rate equation model temperature dependence of the upconverted emission intensities from the 1D 2 level was controlled by the temperature dependence of the excited state absorption coefficient corresponding to the 3F 4 → 1D 2 transition.

Upconversion luminescence of Tm 3+ in Yb 3+-doped fluorophosphate glasses under 683 nm excitation

The upconversion properties of Tm 3+ ions have been studied in fluorophosphate glasses having the composition: 2.67AlPO 4·37.33AlF 3·27PbF 2·(33− x− y) CaF 2· xTmF 3· yYbF 3 under 683 nm light which corresponds to the ground state absorption of the (Tm) 3F 3 level. The absorption, luminescence, excitation and time-resolved spectra and the decay patterns were measured as function of TmF 3 and YbF 3 concentrations at room temperature. Three upconverted emissions centered at 363 ( 1 D 2 → 3 H 6 transition), 451 ( 1 D 2 → 3 H 4 transition) and 478 ( 1 G 4 → 3 H 6 transition ) nm were observed. The emission centered at 478 nm was enhanced in the codoped sample. Two-photon absorption processes are responsible for the upconverted emissions originating from the 1D 2 and 1D 4 levels in both singly and codoped samples, respectively. The upconversion mechanism governing the stepwise excitation of 683 nm light was attributed to the ( Tm) 3 F 4 → ( Yb) 2 F 5 2 and ( Yb) 2 F 5 2 → ( Tm) 1 G 4 energy transfer processes between Tm 3+ and Yb 3+ ions in the codoped sample. According to the time-resolved spectra of the blue emissions, the time at which the upconverted emission reaches its maximum value depends on the Tm concentration. However the ( Tm) 3 F 4 → ( Yb) 2 F 5 2 transfer rate is independent of the Tm 3+ concentration and is equal to 8.8 × 10 3 s −1.

Optical properties and upconverted emissions of Tm 3+ in Yb 3+ doped fluorophosphate glasses

Optical properties of Tm 3+ ions in Yb 3+ doped fluorophosphate glasses containing 27mole% PbF 2 have been studied. The absorption, luminescence and excitation spectra, and the decay patterns were obtained as function of temperature, TmF 3 and YbF 3 concentrations. For the blue emission centered at 479 nm ( 1G 4→ 3H 6 transition) the critical concentration ofTm 3+ is 0.2mole% when the concentration of Yb 3+ is kept constant at 20 mole%. The oscillator strengths of the transitions between J manifolds are calculated by using Judd-Ofelt theory at room temperature and were compared with the ones obtained experimentally. Radiative lifetimes of the excited states are determined and used to obtain nonradiative transition rates and the quantum yields. Unconverted emissions from the 1D 2 , 1G 4 and 3F 4 levels were observed when the Yb 3+ ions were excited with 966 nm light. An absolute upconversion efficiency for the blue (479 nm) and red (791 nm) emissions was obtained using a comparative method at room temperature. The efficiency of the 479 and 791 nm emissions was measured to be 5 × 10 −8 and 7 × 10 −4, respectively, for the sample containing 0.2 mole% TmF 3 and 20 mole% YbF 3 upon 966 nm excitation with an absorbed intensity of 20 mW cm −2. The emission intensity and the decay time of the 1G 4 level were found to be independent of temperature although the emission intensity and the decay time of 3F 4 level show small temperature dependence when the desired level was directly excited. However, the upconverted emission intensity of these levels depends on temperature. This behaviour may be due to a phonon-assisted energy transfer mechanism from Yb 3+ to Tm 3+.

Fluorescence properties of Ho3+doped fluorophosphate glasses

Abstract This paper reports the formation of a new series of Ho3+ -doped fluorophosphate optical glasses in the chemical formulae: 50 (NaPO3)6 + 18 BaF2 + 10 ZnF2 + 20 RF + 2 HoF3 where RF = LiF, NaF, KF, (LiF-NaF), (NaF-KF) and (KF-LiF). The physical properties, absorption and photoluminescene spectra have been measured to understand the optical behaviours of these Ho3+ -glasses as a function of the alkali content changes in the host glass matrices.

Optical properties of a Cr3+-doped fluorophosphate glass investigated by steady state and time-resolved laser spectroscopy

The optical properties of trivalent-chromium-doped fluorophosphate glass (21.74 Al(PO3)3-57.8 BaF2-19.96 AlF3 (wt.%)) have been investigated in the 4.2-300 K temperature range using steady state and time-resolved laser spectroscopy. The luminescence of Cr3+ shows a strong thermal quenching which can be analysed in terms of the quantum mechanical single-configurational coordinate model. In order to establish a correlation between the glass matrix composition and the spectral and temperature behaviour of the Cr3+ photoluminescence, detailed time-resolved measurements have been performed. When compared with fluoride glasses, the results attained for the emission wavelength dependence of the lifetimes and excitation spectra show an enhancement of the site-dependent effects.

Absorption and photoluminescence spectra of Tm3+-doped fluorophosphate glasses

Abstract We have carried out absorption and photoluminescence spectra of six newly prepared TmF3 (2 M%) doped fluorophosphate glasses of composition: (NaPO3)6BaF2ZnF2RF where R = Li, Na, K, (LiNa), (NaK) and (KLi). By evaluating the Judd—Ofelt intensity parameters for the measured absorption levels, the recorded photoluminescence spectra have been analysed to estimate the fluorescent radiative properties (A, AT, βR) and the stimulated emission cross-sections (σEP) of the following luminescence transitions: 1G4→3H6 (λ=451 nm) 1D2→3H4 (λ=468 nm) 3P0→3F2 (λ=482 nm) 1D2→3H5 (λ=492 nm) These have been determined in order to understand the alkali effects on the Tm3+-optical glasses studied.

Photoluminescence spectra of Er3+-doped fluorophosphate glasses

Abstract This short paper reports various physical, absorption and emission properties of the Er3+-doped glasses based on the (NaPO3)6 as the major constituent by changing the cations (Li, Na & K) both in mixed and unmixed forms. The obtained results show that the optical properties are found interesting in glass-B which contains, 20M% NRF as the network modifier.

Time-resolved fluorescence and energy transfer of Cu +- doped fluorophosphate glass

Time-resolved fluorescence of Cu + in fluorophosphate glass by excitation at different wavelengths have been conducted at room or low temperatures. The fluorescence lifetimes at different emission wavelengths have also been determined. The peak position of fluorescence spectra shifts to longer wavelength with increasing delay time. Meanwhile, by excitation at longer wavelength, some additional peaks rise on each side of the original one, which shows the energy transfer among activated ions.

Gain saturation in Nd:doped laser materials

Saturation of gain in Nd:doped silicate, phosphate, and fluorophosphate glasses, and in doped crystals of YAG and YLF was observed during amplification of 1064 and 1053 nm pulses with durations of 1.0, 9.0, and 50 ns. Saturation fluences were computed from measured external parameters by means of the Frantz-Nodvik model for a homogeneous amplifier. The resulting values of saturation fluence increase with increasing output fluence and were only slightly greater at 50 ns than at 1 ns, suggesting that the lower level lifetime is less than 1 ns.

SELECTIVE EXCITATION OF NARROW LINES IN Nd3+ DOPED LASER GLASSES

Using a narrow line output of tunable pulsed dye laser, the inhomogeneously broadened absorption band of 4I9/2→4G5/2 in Nd3+ doped germate, silicate, phosphate, fluo-rophosphate and fluoroberyllate glasses were selectively excited at low and room temperatures. Wavelength dependence of fluorescence decay were observed to investigate the decay nature and interaction of Nd3+ ions at different site in different glass hosts.