Kelly L. Nash

Absorption intensities and emission cross sections of Tb3+ (4f8) in TbAlO3

Trivalent terbium absorption intensities in single-crystal TbAlO3 are analyzed using the Judd-Ofelt model to assess the crystal’s potential as a solid state laser system. The standard Judd-Ofelt model was applied to the room temperature absorption intensities of Tb3+ (4f8) to determine the phenomenological intensity parameters Ω2, Ω4, and Ω6. Seven multiplet manifolds are identified and the absorption intensities of these manifolds are least-squares fitted to the calculated intensities to obtain the intensity parameters: Ω2=40.52×10−20cm2, Ω4=8.74×10−20cm2, and Ω6=2.26×10−20cm2 in TbAlO3. These intensity parameters are then applied to determine the radiative decay rates and branching ratios of Tb3+ transitions from the D45 to the FJ′7 multiplet manifolds. Based on the results, the radiative lifetime of the excited state manifold D45 is determined from the radiative decay rates and found to be 3.5ms. The calculated lifetime is longer than the measured lifetime, reflecting the nonradiative interactions betw...

Modeling optical transitions of Er3+(4f11) in C2 and C3i sites in polycrystalline Y2O3

The optical properties of Er3+ in polycrystalline (ceramic), and nanocrystalline forms of cubic (bixbyite) yttrium oxide are modeled based on the absorption spectra obtained between 400 and 1700 nm and the fluorescence spectra observed between 1500 and 1670 nm. Both spectra were obtained at 8 K. The observed crystal-field splitting and the measured intensities of transitions between Stark levels of the L2S+1J multiplet manifolds of Er3+(4f11) in both the C2 and C3i sites of Y2O3 are analyzed in terms of established models. The inversion symmetry of C3i sites limits the observed electronic transitions to magnetic dipole transitions between the I413/2 and I415/2 manifolds. There is no spectroscopic evidence for transitions involving other multiplet manifolds of Er3+ ions in C3i sites. For Er3+ ions in C2 sites, forced electric dipole transitions are allowed between the J+12 Stark levels associated with each manifold. With few exceptions, the crystal-field splitting and the intensities of the transitions bet...

Absorption intensities and emission cross section of intermanifold transition of Er3+ in Er3+:Y2O3 nanocrystals

The room temperature absorption intensities of Er3+(4f11) transitions in synthesized Er3+:Y2O3 nanocrystals have been analyzed using the Judd-Ofelt (J-O) model in order to obtain the phenomenological intensity parameters. The J-O intensity parameters are subsequently used to determine the radiative decay rates, radiative lifetimes, and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds LJ2S+1 of Er3+(4f11). The emission cross section of the important intermanifold Er3+ I13∕24→I15∕24 (1.5μm) transition has been determined. The room temperature fluorescence lifetime of this transition in Er3+:Y2O3 nanocrystals was measured. From the radiative lifetime determined from the J-O model and measured fluorescence lifetime, the quantum efficiency of this material was determined. The comparative study of Er3+(4f11) ions suggests that synthesized Er3+:Y2O3 nanocrystals could be an excellent alternative to single crystal Er3+:Y2O3 for certai...

Optical intensity analyses of Er3+:YAlO3

Analyses of the optical absorption and emission intensities are performed on Er3+ ions doped into yttrium orthoaluminate YAlO3 to assess this material as a laser source. The Judd–Ofelt model is applied to the room temperature absorption intensities of Er3+ in YAlO3 to obtain the phenomenological intensity parameters: Ω2=1.06×10−20 cm2, Ω4=1.96×10−20 cm2, and Ω6=1.40×10−20 cm2. The intensity parameters are used to determine the radiative decay rates and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Er3+ in YAlO3. Using the radiative decay rates, radiative lifetimes of 13 excited states have been determined. The room temperature fluorescence lifetime of the Er3+ S43/2→I415/2 transition is measured to be 0.43 ms. Values of emission cross section and peak emission cross section have been obtained for the Er3+ I413/2→I415/2 and S43/2→I415/2 intermanifold transitions. The detailed structure observed in the manifold-to-m...

Optical absorption intensity analysis and emission cross sections for the intermanifold and the inter-Stark transitions of Nd3+(4f3) in polycrystalline ceramic Y2O3

Spectroscopic properties have been characterized for trivalent neodymium doped polycrystalline ceramic ytttria, Nd3+:Y2O3. The Judd-Ofelt [Phys. Rev. 127, 750 (1962); J. Chem. Phys. 37, 511 (1962)] analysis has been applied to the room temperature absorption spectrum to determine the radiative decay rates and branching ratios of Nd3+ transitions from the F3∕24 metastable manifold to the IJ4 lower-lying multiplet manifolds. The quantum efficiency is determined from the measured fluorescence lifetime and the radiative lifetime of the F3∕24 manifold state. In addition, a detailed characterization of the Stark energy levels of the I9∕24 and I11∕24 manifolds has been performed using the room temperature fluorescence spectra for the F3∕24→I9∕24 and F3∕24→I11∕24 transitions of Nd3+(4f3) in ceramic Y2O3. The emission cross sections of the F3∕24→I9∕24 and F3∕24→I11∕24 intermanifold transitions have been determined. Also, the peak emission cross sections of the principal inter-Stark peak transitions R1→X5 and R1→Y2...

Analyses of 4f11 Energy Levels and Transition Intensities Between Stark Levels of Er3+ in Y3Al5O12

ABSTRACT Absorption and fluorescence spectra obtained at temperatures as low as 4 K were investigated between 200 and 1550 nm on samples containing approximately 1.2 at. wt. % Er in Y3Al5O12 (YAG). Within this wavelength range 125 experimental energy (Stark) levels were analyzed, representing data that span 29 2S+1 L J multiplet manifolds of Er3+(4f11) in D2 sites up to an energy of 44,000 cm−1. Agreement between calculated and observed Stark levels was achieved with an r.m.s. deviation of 11.2 cm−1. These transitions originate from the ground-state Stark level in the 4I15/2 manifold to J + 1/2 Stark levels associated with each of the 28 excited-state manifolds. A total of 88 ground-state absorption transition line strengths were measured for 19 2S+1 L J multiplet manifolds between 280 and 1550 nm. For line strength measurements, the Er3+ ion is assumed to be distributed homogeneously throughout the D2 cation sites of Y3+ in the lattice. The line strengths were analyzed with a weighted (E i − C i )/E i , with an r.m.s. error of 0.25. Use of a “vector crystal field” parametrization resolves ambiguities in the transition intensity parameters and allows for the definition of polarization-resolved Judd-Ofelt parameters, which may have wide-ranging applicability for future Judd-Ofelt-type intensity calculations.

Comparative study of the crystal-field splitting of trivalent neodymium energy levels in polycrystalline ceramic and nanocrystalline yttrium oxide

Absorption and fluorescence spectra of commercially available polycrystalline ceramic Nd3+:Y2O3 and nanocrystalline aggregates of Nd3+:Y2O3 grown in our laboratory are optically characterized at nominal 8K and room temperature. In comparing the spectra obtained from these two different sources, we find similarities in terms of the detailed crystal-field splitting of the energy levels of the Nd3+ ion in the Y2O3 host. The 8K spectra are analyzed for the energy (Stark) level transitions between the LJ2S+1 multiplet manifolds of Nd3+(4f3). The analysis includes the manifolds of I9∕24 (the ground state), I11∕24, I13∕24, I15∕24, F3∕24, F5∕24, H9∕22, F7∕24, S3∕24, and F9∕24. The results of this study are also compared with a crystal-field splitting analysis reported earlier for single-crystal Nd3+:Y2O3 grown by a modified flame fusion method. We find that the spectroscopic properties of our composites compare favorably with other ceramic and single-crystal forms of Nd3+:Y2O3 currently available.

Intensity analysis and energy-level modeling of Nd3+ in Nd3+:Y2O3 nanocrystals in polymeric hosts

Optical absorption and emission intensities are investigated for Nd3+ in nanocrystalline Nd3+:Y2O3. Room temperature absorption intensities of Nd3+(4f3) transitions in synthesized Nd3+:Y2O3 nanocrystals have been analyzed using the Judd–Ofelt (J-O) approach to obtain the phenomenological intensity parameters. The J-O intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Nd3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Nd3+(4f3). The emission cross sections and room temperature fluorescence lifetimes of the important intermanifold F43/2→I4J (J=9/2,11/2,13/2,15/2) transitions have been determined. We also compare the spectra of the Nd3+:Y2O3 nanocrystals to those of the nanocrystals embedded in polymeric matrices of epoxy and chitosan, and we find similarities in terms of the detailed Stark energy levels of the Nd3+ ion in the Y2O3 nanocrystalline host. The 300 K sp...

Intensity analysis and crystal-field modeling of Ho3+ in KPb2Cl5 host

Optical absorption and emission intensities are investigated for Ho3+ doped into single-crystal KPb2Cl5. Room temperature absorption spectra of Ho3+(4f10), representing transitions from I58 to excited multiplet manifolds observed between 400 and 2100 nm, have been analyzed using the Judd–Ofelt (JO) model to obtain the phenomenological intensity parameters Ω2, Ω4, and Ω6. The JO intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Ho3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Ho3+. The room temperature fluorescence spectrum in the near infrared region is reported between 850 and 1550 nm. The emission cross section for the intermanifold transition, F55→I57 (0.98 μm) has been determined. The 8 K absorption spectrum was examined as well. The detailed structure observed in the absorption bands I57, S52, F54, and F53, was analyzed in terms of the crystal-field split...

Spectral analysis of synthesized nanocrystalline aggregates of Er3+:Y2O3

The absorption and fluorescence spectra of nanocrystalline aggregates of Y2O3 doped with Er3+ are reported between 8K and room temperature. The nanocrystalline particles were synthesized from a homogenous solution of the metal ions and urea at elevated temperatures in order to control the precipitation of the mixed hydroxides by a slow uniform reaction throughout the solution. The morphology of the calcinated materials revealed uniformly spherical aggregates 200nm or less depending on the ratio of the metal ions in the initial solution. Spectra obtained from these particles were analyzed in detail for the crystal-field splitting of the LJ2S+1 multiplet manifolds of Er3+(4f11) including the ground-state manifold I15∕24, and excited manifolds I9∕24, F9∕24, S3∕24, H11∕22, F7∕24, F5∕24, and F3∕24. Fluorescence lifetimes and results from an analysis of the intensities of manifold-to-manifold transitions are also reported. The sharp-line absorption and emission spectra are comparable to spectra reported earlier...