Spontaneous Radiative Transition Probabilities Research Articles

Effect of ZnO on spectroscopic properties of Sm3+ doped zinc phosphate glasses

Spectroscopic properties of Sm3+ containing zinc oxide based phosphate glasses in the chemical composition (50−x)P2O5+20Na2HPO4+9AlF3+xZnO+1Sm2O3 (where x=5, 10, 15, 20 and 25) have been studied. Raman, optical absorption, emission spectra and luminescence decay profiles were recorded and systematically analyzed. Using Judd–Ofelt theory, Judd–Ofelt intensity parameters Ωλ (λ=2, 4 and 6), spontaneous radiative transition probabilities (Arad), radiative lifetimes (τR), branching ratios (β) were calculated and discussed. With 400nm wavelength excitation, the emission spectra and decay lifetime of 4G52 level of Sm3+ doped zinc-phosphate glasses were studied. The branching ratios and emission cross-sections for the transition, 4G5/2→6H7/2 are found to be higher for x=25mol% of zinc-phosphate glass matrix. The observed decay profiles were found to be exhibiting non-exponential behavior for all zinc-phosphate glasses, due to non-radiative energy transfer among the excited Sm3+ ions.

Optical spectroscopy and population behavior between ^4I_11/2 and ^4I_13/2 levels of erbium doped germanate glass

In this paper, mid-infrared emission properties and energy transfer mechanism were investigated in Er3+ doped germanate glass pumped by 980 nm diode laser. Spontaneous radiative transition probability and emission cross section at 2.7 μm were calculated to be as high as 36.45 s−1 and 1.61 × 10−20 cm2, respectively. Corresponding upconversion emission spectra and radiative lifetimes of 4I13/2 level were determined to elucidate the mid-infrared luminescent characteristics. Moreover, population behaviors of Er3+: 4I11/2 and 4I13/2 level were analyzed numerically via Inokuti-Hirayama model, rate equations and Dexter’s theory. In addition, DSC curves of developed samples were measured and thermal stabilities were studied to evaluate the ability of resisting thermal damage and crystallization. The results indicate that erbium activated germanate glass is a promising candidate for mid-infrared applications. This work may provide beneficial guide for investigation of population behaviors of Er3+ ions at 2.7 μm emissions.

Enhancement of 1.53 μm emission in erbium/cerium-doped germanosilicate glass pumped by common 808 nm laser diode.

Erbium-doped germanosilicate glasses with various cerium ions contents have been prepared. Optical absorption and 1.53 μm emission spectra were measured to characterize the spectroscopic performances of prepared samples. A detailed study of 1.53 μm spectroscopic properties was carried out when pumped by an 808 nm laser diode. Moreover, an energy level diagram and an energy transfer mechanism between Er3+ and Ce3+ were proposed to elucidate the enhanced 1.53 μm fluorescence. It is found that the prepared samples have optimal spectroscopic properties when the Ce3+ concentration is fixed to 0.5 mol. %. High spontaneous radiative transition probability (172.66 s(-1)), large effective emission bandwidth (74 nm), and emission cross section (9.49×10(-21) cm(2) indicate that 808 nm pumped Er3+/Ce3+ codoped germanosilicate glass might be a suitable material for a broadband optical amplifier.

1.53 μm emission properties in Er3+ doped Y2O3 and Nb2O5 modified germanate glasses for an optical amplifier

Er3+ doped Y2O3 and Nb2O5 modified germanate glasses have been reported which possesses excellent thermal stability. Near infrared emission characteristics upon excitation of a conventional 980nm laser diode have been investigated. According to absorption spectra and refractive index, Judd–Ofelt intensity parameters, spontaneous radiative transition probabilities, radiative lifetimes and stimulated emission cross sections have been calculated and discussed. These results indicate that the predicted spontaneous transition probability and emission cross section of Er3+:4I13/2→4I15/2 transition in developed glasses can reach as large as 192.39s−1 and 7.14×10−21cm2, respectively. Hence, germanate glasses with superior performances might be a useful material for applications in optical amplifiers around 1.53μm.

OPTICAL ABSORPTION AND STRUCTURAL STUDIES OF Pr3+ DOPED CADMIUM BISMUTH BORATE GLASSES IN VISIBLE AND NEAR INFRARED REGIONS

Glasses having composition 20CdOxBi2O3(79.5-x)B2O30.5Pr6O11 with x varying from 15 to 35 mol% have been synthesized. Optical absorption and fluorescence spectra were measured at ambient temperature. A close correlation is observed between the Bi2O3 content and the spectroscopic properties such as Judd-Ofelt intensity parameters Ωλ = (λ = 2, 4, 6) , radiative and structural properties of prepared glasses doped with Pr3+ ion. The variation of Ω2 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth (RE) ion site (due to structural change) and to changes in RE-O covalency, whereas the variation of Ω6 has been related to the variation in RE-O covalency. Following the luminescence spectra, various radiative properties like transition probability (Arad), radiative lifetime (τr), branching ratio (βr) and stimulated emission cross section (σ) have been calculated. The branching ratio for 3P0 → 3F2 transition of Pr3+ glass system arrive at 41 to 40%, respectively, and the predicted spontaneous radiative transition probability rates are high and varies from 14032 to 14864 s−1. In addition, the glass stability is improved in which the substitution of B2O3 for Bi2O3 strengthens the glass network structure. The bismuth based glass as a host for Pr3+ ion doped suggesting their suitability for laser applications.

PHYSICAL, ABSORPTION AND FLUORESCENCE SPECTRAL STUDIES OF Pr3+ IONS DOPED LITHIUM BISMUTH BORATE GLASSES

Glasses of the system: xB2O3-10Bi2O3-30Li2O-xPr6O11 where x =1, 1.5 and 2 were prepared by melt quenching technique. Optical absorption and emission spectra have been recorded. The intensities of f-f transition are calculated in term of Judd-Ofelt (JO) intensity parameters Ωλ (λ = 2, 4 and 6). Using the fluorescence data and these Ωλ parameters, various radiative properties like transition probability (Arad), branching ratio (βR), radiative lifetime (τR), and stimulated emission cross section (σp), of various emission lines have been evaluated. The branching ratio for 3P0→3H4 transition is 56% and the predicted spontaneous radiative transition probability rates are fairly high 16411 s−1. This is beneficial for lasing emission.

Structural, absorption and fluorescence spectral analysis of Pr 3+ ions doped zinc bismuth borate glasses

Glasses having composition 20ZnO· xBi 2O 3·(79.5 − x)B 2O 3·0.5Pr 6O 11 were prepared by melt quench technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. The spectroscopic properties of these glasses were investigated by recording optical absorption and fluorescence spectra. The structural investigations of the glasses were carried out by recording the IR spectra. The optical properties of Pr 3+ ions doped zinc borate glasses with varying concentration of bismuth oxide have been studied. The Judd–Ofelt intensity parameters Ω λ ( λ = 2, 4, 6) and other radiative properties like radiative transition probability, radiative life time, branching ratio and stimulated emission cross-section of the prepared glasses have been calculated. The variation of Ω 2 with Bi 2O 3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth oxygen ( RE-O) covalency. The branching ratio for 3P 0 → 3F 2 transition is 42% and the predicted spontaneous radiative transition probability rates are fairly high (14,347–14,607 s −1). This is beneficial for lasing emission. The stimulated emission cross-section for all the emission bands has been calculated.

Spectroscopy of the Bi 4Si 3O 12:Er 3+ glass for optical amplification and laser application

Spectroscopic characterization for optical amplification and laser application of the Er 3+-doped Bi 4Si 3O 12 glass is performed through its absorption and luminescence spectra. The spontaneous radiative transition probabilities from the first seven excited states to the ending states are calculated to obtain the luminescence branching ratios and radiative lifetimes. Intense infrared to visible luminescence of the Er 3+ ion is observed with 4I 9/2 state excitation (800 nm) under a 200 mW laser excitation power. The value obtained for the ratio of the 4I 11/2 → 4F 7/2 excited-state absorption oscillator strength to the 4I 15/2 → 4I 11/2 ground state absorption oscillator strength is in accordance with those reported for Er 3+-doped materials pumped efficiently at 4I 11/2 level excitation wavelengths. Gain cross-section spectra as a function of the inverted population rate and the stimulated emission cross-section spectrum were determined for the 4I 13/2 → 4I 15/2 infrared (IR) laser transition. The large gain bandwidth of the 4I 13/2 → 4I 15/2 IR emission has resulted in being close to those reported for Er 3+-doped oxide glasses suitable for broadband amplifiers.

Tm 3+ doped Bi 2O 3–GeO 2–Na 2O glasses for 1.8 μm fluorescence

53.3BiO 1.5–33.3GeO 2–13.4NaO 0.5 (cation%) glasses with various Tm 3+ concentration were prepared by melt-quenching method. These glasses show high density, high refractive index, low phonon energy and good stability against crystallization. Absorption spectra of Tm 3+-doped bismuthate glass were measured to obtain the radiative lifetimes by Judd-Ofelt theory. The absorption (4.5 × 10 −21 cm 2) and emission (6.7 × 10 −21 cm 2) cross-sections were calculated by Beer–Lambert and McCumber theory. The results show that the Tm 3+ ( 3F 4 → 3H 6) in these glasses have high spontaneous radiative transition probabilities and large stimulated emission cross-section. Then the fluorescence emission spectra were measured under 808 nm excitation and the maximum emission intensity at 1.8 μm is obtained at 0.9 mol% Tm 2O 3 in the glasses.

Investigation of 2.0 μm emission in Tm 3+ and Ho 3+ co-doped TeO 2–ZnO–Bi 2O 3 glasses

Tm 3+ and Ho 3+ co-doped TeO 2–ZnO–Bi 2O 3 (TZB) glasses were prepared by the conventional melt-quenching method. Two micrometre emission properties of the TZB glasses exited by 808 nm Laser Diode (LD) were analyzed and discussed. The Judd–Ofelt parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho 3+ were calculated based on the absorption spectra by using Judd–Ofelt theory. The absorption spectra and fluorescence spectra were measured. The predicted spontaneous radiative transition rate of 5I 7 → 5I 8 of Ho 3+ is as high as 466.8 s −1. The result of fluorescence spectra indicates that the maximum emission intensity of Ho 3+ 2.0 μm and of Tm 3+ 1.47 μm emission can be achieved at the concentration of 1 mol% Tm 2O 3 and 1 mol% Ho 2O 3 in TZB glasses. The maximum absorption and emission cross-section of Ho 3+ near 2.0 μm are 0.87 × 10 −20 cm 2 at 1951 nm and 1.07 × 10 −20 cm 2 at 2047 nm, respectively.

Investigation of 2.0 μm emission in Tm 3+ and Ho 3+ co-doped oxyfluoride tellurite glass

This paper reports 2.0 μm emission properties of Tm 3+/Ho 3+ co-doped oxyfluoride tellurite glass exited by 808 nm laser diode (LD). Mid-infrared transmittance property of glass was investigated by Fourier transform infrared (FTIR) spectrometer. The real chemical composition of investigated glass was identified by X-ray photoelectric spectroscopy (XPS). Thermal stability of the glass was determined by differential thermal analysis (DTA) measurement. The Judd–Ofelt parameters, spontaneous radiative transition probabilities, branching ratios and radiative lifetime of Ho 3+ were calculated based on the absorption spectra by using Judd–Ofelt theory. Results indicate that the maximum 2.0 μm emission intensity attributed to the 5I 7→ 5I 8 transition of Ho 3+ was achieved at 1.5 mol% Tm 2O 3 and 1 mol% Ho 2O 3 concentrations in oxyfluoride tellurite glass. OH − absorption at 3000 cm −1 was greatly depressed by introduction of 10 mol% F −. The maximum absorption and stimulated emission cross-section of Ho 3+ near 2.0 μm are 7.0×10 −21 cm 2 at 1950 nm and 8.8×10 −21 cm 2 at 2048 nm, respectively. The calculated radiative lifetime of 4.4 ms for 5I 7→ 5I 8 transition and large stimulated emission cross-section of the Tm 3+/Ho 3+ co-doped oxyfluoride tellurite glass indicate that the glass has a potential application in efficient 2.0 μm laser.

Comparison of optical parameters and luminescence between Er3+/Yb3+ codoped phosphate glass ceramics and precursor glasses

Er 3 + / Yb 3 + codoped transparent phosphate precursor glasses and glass ceramics have been fabricated and characterized. The formation of ErPO4 and YbPO4 nanocrystals was studied using x-ray diffraction. The intensity parameters, the spontaneous radiative transition probabilities, the branching ratios, and the radiative lifetimes of Er3+ in both glass ceramics and precursor glasses were calculated based on the Judd–Ofelt theory, and the crystallization process in the glass ceramics is confirmed by the optical parameters obtained. Under 975 nm wavelength excitation intense 1.54 μm fluorescence and upconversion luminescence were observed in the glass ceramics, the quantum efficiency of the Er3+ I413/2→I415/2 transition is 95%, and the transition mechanisms of the upconversion luminescence are due to a two-photon process.

Mid-Infrared Emission Characteristic and Energy Transfer of Ho3+-Doped Tellurite Glass Sensitized by Tm3+

We report on 2.0-microm emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+ upon excitation of a conventional 808 nm laser diode. The Judd-Ofelt strength parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho3+ have been calculated from the absorption spectra by using the Judd-Ofelt theory. Significant enhancement of 2.0-microm emission of Ho3+ has been observed with increasing Tm3+ doping up to 0.7 mol%. The energy transfer coefficient of the forward Tm3+-->Ho3+ is approximately 17 times larger than that of the backward Tm3+<--Ho3+ energy transfer. Our result indicates that the maximum gain of 2.0-microm emission, assigned to the transition of (5)I7-->(5)I8 of Ho3+, might be achieved from the tellurite glass at the concentration of 0.5 mol% of Tm2O3 and 0.15 mol% of Ho2O3. The high gain coefficient and quantum efficiency (1.16) along with the large value of the product of the stimulated emission cross-section and the measured radiative lifetime (4.12 x 10(-27) m(2)s) of the Ho3+/Tm3+-codoped tellurite glasses might find potential applications in efficient 2.0-microm laser.

Thermal stability and optical transitions of Er3+/Yb3+-codoped barium gallogermanate glass

Er3+/Yb3+-codoped barium gallogermanate glass that is suitable for use in fiber lasers and optical waveguide devices has been fabricated and characterized. The differential scanning calorimetry, absorption spectra, infrared fluorescence and upconversion luminescence spectra of the glass have been measured. The spontaneous radiative transition probability, branching ratio, and radiative lifetime of the optical transitions have been calculated by using the Judd–ofelt theory. Differential scanning calorimetry result suggests that it is suitable to be a potential candidate for fiber drawing. Intense infrared fluorescence at 1531nm and bright visible upconversion luminescence have been observed under 980nm laser diode excitation at room temperature. The quadratic dependence of the upconversion emission on the excitation power indicates that two-photon steps are involved for the three visible emission bands. The possible upconversion mechanisms have also been discussed. All the results reveal that the Er3+/Yb3+-codoped barium gallogermanate glass fabricated in our work could be a suitable candidate for upconversion and infrared applications.

희토류 첨가 광소재의 나노구조 : Dy 첨가 Ge-As-S 유리의 X-선 흡수 스펙트럼 분석

Dy L₃-edge XANES and EXAFS spectra of chalcogenide Ge-As-S glass doped with ca. 0.2 wt% dysprosium have been investigated along with some reference Dy-containing crystals. Amplitude of the white-line peak in XANES spectrum of the glass sample turns out to be stronger than that of other reference crystals, i.e., Dy₂S₃, Dy₂O₃, and DyBr₃. It has been verified from the Dy L₃-edge EXAFS spectra that a central Dy atom is surrounded by 6.7±0.5 sulfur atoms in its first coordination shell in the Ge-As-S glass, which is relatively smaller than 7.5 of the Dy₂S₃ crystal. Averaged Dy-S inter-atomic-distance of the glass (2.78±0.01 A) also turns out to be somewhat shorter than that of the Dy₂S₃ crystal (2.82±0.01 A). Such nanostructural changes occurring at Dy atoms imply there being stronger covalency of Dy-S chemical bonds in the Ge-As-S glass than in the crystal counterpart. The enhanced covalency in the nanostructural environment of Dy 3+ ions inside the glass would then be responsible for optical characteristics of the 4f ↔ 4f transitions of the dopants, i.e., increase of oscillator strengths and spontaneous radiative transition probabilities.

Optical spectroscopy of Er3+ ions in poly(acrylic acid)

Abstract Er 3+ -doped poly(acrylic acid) was synthesized by polymerization in aqueous solution of the monomer partially neutralised with erbium hydroxide. 13 C NMR spectra confirmed the monomer modification. Absorption intensity data of the Er 3+ lanthanide ion in poly(acrylic acid) (PAA) are analysed using the Judd and Ofelt (JO) phenomenological treatment in order to understand its optical properties for laser application. The intrinsic emission of PAA gives rise radiative energy transfer between the host and Er 3+ ions. The measured and calculated oscillator strengths for transitions from the ground state to excited multiplets compare favourably within the typical uncertainties associated with the JO formalism. Then, the spontaneous radiative transition probabilities from the former 11 excited states to diverse ending states were computed to obtain the luminescence branching ratios as well as the radiative lifetimes.

Rovibrational distribution determination of H2 in low temperature plasmas by Fulcher-α band spectroscopy

It is proposed that the rotational and vibrational temperatures of H2 can be derived from the fitting to the H2 Fulcher band line emissions. However, the fitting relies on the employed spontaneous radiative transition probabilities and the excitation rate coefficients, which are dependent on the vibrational and rotational quanta in each electronic state. From our study, it is found that, in low temperature plasmas both the Fulcher-α radiative transition and the electron impact excitation to the d 3 Πu state from the ground electronic state deviate significantly from the Franck–Condon approximation. The vibrationally resolved complete sets of the cross sections are calculated based on the semi-classical Gryzinski theory, and the Fulcher band transition probabilities are obtained based on the newest published data on the electronic transition moment and the solution to the radial Schrödinger equation. The fitting to experimental line emissions shows that Boltzmann's Law can be employed for the distribution of vibrational (in lower level), and particularly for the rotational, populations in the ground electronic state of H2 in low temperature plasmas.

New measurements of spontaneous transition probabilities for beryllium-like ions

The authors describe measurements of spectral line intensities for pairs of transitions having common upper levels and thus derive the branching ratios of their spontaneous radiative transition probabilities. These are then combined with the results of measurements of the radiative lifetimes of the upper levels by other authors to obtain values of the individual probabilities. Care was taken to avoid the effects of the trapping of resonance radiation, which could have invalidated the results. A particular feature of their measurements was the use of two spectrometers, spanning between them the wavelength range from less than 100 AA to over 7000 AA. The results are for transitions in N IV, O V and Ne VII and are given with a claimed accuracy of between 7 and 38%. These are compared with theoretically calculated values. Good agreement is found for some of the simpler electric dipole transitions. On the other hand, for some of the other transitions, which in certain cases are only possible because o configuration interaction, disparities between their measurements and theory are as large as a factor of five.

The Measurement of Branching Ratios of Spontaneous Radiative Transition Probabilities for Be-Like Ions N IV and O V

In an experiment to measure emission line intensities from the Belike ion Ne VII (Lang 1983), the intensity ratio I(2s3s3S−2s3p3P)/I(2p23P−2s3p3P) was found to be a factor six larger than predicted from the ratio of the theoretical spontaneous radiative transition probabilities (A values). Indeed, to reconcile the Ne VII experiment and theory in several respects it was suggested also that in Be-like C III the theoretical ratios I(2s3s1 S−2s3p1P)/I(2p21D−2s3p1P) was about a factor three too low.The same apparatus was used to measure A value ratios in Be-like N IV and 0 V. Briefly the 40 kJ θ-pinch plasma source was viewed radially using a m Ebert and a l m grazing incidence photoelectric spectrometer. The m Ebert was intensity calibrated from 7300 Å to 3600 Å using a tungsten filament lamp, and from 3800 Å to 2500 Å using a deuterium lamp, both lamps having been calibrated by NPL. As described fully by Lang (1983), the branching-ratios method was used to calibrate the front exit slit of the grazing incidence instrument in the wavelength range 88 Å to 500 Å. Only Li-like line pairs of those listed in that paper were used with the addition of the C IV doublets 2s2S−3p2P (312.4 Å) and 3s2S−3p2P (5801.33 Å, 5811.98 Å). The H-like ion He II 1–4 transition (243.0 Å) and 3–4 transition (4685.7 Å) were used to cross-check the calibration. As shown in the figure, the He II result agrees excellently with the calibration as defined from the Li-like lines.

Experimental Determination of the Oscillator Strength of the Violet System of OH

The radiative lifetime of the A 2Σ→X 2Π transition of OH has been measured. The apparent lifetime is dependent upon the pressure of the parent molecule from which OH* is produced by electron bombardment. Extrapolation to zero pressure yields a spontaneous radiative transition probability of 0.99×106 sec—1 corresponding to an oscillator strength f= (7.25±0.5) 10—4. This value assumes that the electronic transition moment is constant over the (0, 0) vibrational transition. Utilizing Learner's values of rotation—vibration interaction an f value for the rotationless molecule and the (0, 0) band is f= (8.0±0.8) 10—4. The collisional quenching cross sections between OH* and water or methanol are 70×10—16 cm2 and 110×10—16 cm2, respectively.