Baldassare Di Bartolo

Branching ratios, cross sections, and radiative lifetimes of rare earth ions in solids: Application to Tm3+ and Ho3+ ions in LiYF4

The measurement of branching ratios, cross sections and radiative lifetimes for rare earth ions in solids is considered. The methods are applied to Tm and Ho in YLF as a test case. De-activation rates for electric dipole and magnetic dipole emission are calculated for many of the lower lying manifolds in Tm:YLF and Ho:YLF in the context of the Judd-Ofelt theory to determine radiative lifetimes. Measured values for the branching ratios as well as the absorption and emission cross sections are also presented for many of the excited state manifolds. From these measurements, a methodology is developed to extract measured values for the radiative lifetimes. These results are compared with the Judd-Ofelt theory as a guide for consistency and for determining the accuracy of the Judd-Ofelt theory in predicting branching ratios and radiative lifetimes. The parameters generated by the methods covered here have potential applications for more accurate modeling of Tm:Ho laser systems.

Advances in nonradiative processes in solids

Nonradiative Relaxation of Solids: Different Pathways to the Ground State.- The Role of Nonradiative Processes in the Spectroscopy of Optically Active Centers in Solids.- Radiative and Nonradiative Rates in Luminescence Centers.- Advances in Non-Radiative Processes in Solid State Laser Materials.- Model Calculations of Nonradiative Multiphonon Processes in INORGANIC Insulating Solids.- Advances in Nonradiative Processes in Semiconductors.- Radiative and Nonradiative Processes in Color Centers.- Nonradiative Transitions Between Electronic Levels of Opticallyactive Ions in Glass.- Nonradiative Processes in Luminescent Materials: A Materials Scientists View.- Techniques for the Investigation of Nonradiative Processes.- New Applications of Efficient Phosphors.- Long Seminars.- Energy Transfer in Cr, Tm: Yag.- Luminescence and Nonradiative Processes in Porous Glasses.- Laser Spectroscopy Techniques Applied to Cr3+ -Doped Materials.- How to Play with Springs and Pulses in a Classical Harmonic Crystal.- Thermal Response and Decoupling of Excitations at Low Temperatures.- New Laser Crystals (Abstract only).- Degenerate Four-Wave Mixing Technique for Studying Very Fast Radiationless Processes in Very Short Time Scale.- Photothermal Optical Nonlinearities, Optical Bistability and Possible Applications.- Crystals: Growth Methods and Characterization.- 4He and 3He Calorimetric Absorption Spectroscopy: Principles and Results on Ingaas/Alinas Quantum Wells and Fe in InP and GaAs.- Special Topics (Abstracts).- Particles and Elementary Excitations.- Short Seminars (Abstracts).- Excited State Absorption in Tb Activated Phosphor Powders.- Picture of the Participants.- Participants.

On the distribution of energy between the Tm 3F4 and Ho 5I7 manifolds in Tm-sensitized Ho luminescence

Abstract A theory on the distribution of energy between the Tm 3 F 4 and Ho 5 I 7 manifolds in Tm-sensitized Ho materials is presented. A rate equation approach is utilized to arrive at an expression for the temperature-dependent equilibrium constant, Θ. Experimental support for this calculation is obtained by two different experimental procedures. Approximations used in the theory and the limits of applicability are also discussed. In the course of the development of the theory, a distinction is made between low and high excitation regimes, and criterion for applicability are given. Equations for the fractional population of Tm and Ho ions of the total excited state population in the low excitation density limit are derived in the context of the present theory, which differ from those widely used in the literature.

Spectroscopy and dynamics of collective excitations in solids

Nonlinear Optics and Collective Excitations N. Bloembergen. Fundamentals of Spectroscopy of Collective Excitations in Solids B. Di Bartolo. Light-Matter Interaction: Experimental Aspects C. Klingshirn. Theoretical Description of Collective Excitations: Bloch Equations and Relaxation Mechanisms R. Zimmerman. Linear and Nonlinear Optical Spectroscopy: Spectral, Temporal and Spatial Resolution J.M. Hvam. The Study of Collective Excitations in Solids by Inelastic Neutron Scattering: T. Riste. Excitation Dynamics in Organic Molecules, Solids, Fullerenes, and Polymers P. Prasad. The IR Vibrational Properties of Composite Solids and Particles: The Lyddane-Sachs-Teller Relation Revisited A.J. Sievers. Intrinsic Localized Modes in Anharmonic Lattices A.J. Sievers, et al. Plasmons and Surface Plasmons in Bulk Metals, Metallic Clusters,and Metallic Heterostructures R.V. Baltz. Enlightenment of Luminescent Materials C.R. Ronda. Spectroscopy and Development of Solid Sate Layers at NASA N.P. Barnes. Optical Excitation and Relaxation of Solids with Defects B. Baldacchini. Newly Developed Solid State Lasers R. Reisfeld. Energy Transfer and Migration of Excitation in Solids and Confined Structures F. Auzel. 45 Additional Articles. Index.

Spectroscopy and lasing characteristics of Nd-doped Y 3 Ga x Al (5–x) O 12 materials: application toward a compositionally tuned 0.94-μm laser

Nd-doped Y3GaxAl(5-x)O12 (YGAG) materials are investigated for their usefulness as compositionally tuned laser materials. An analysis of line-center wavelength, line broadening, and line strength with Ga concentration is conducted to assess the feasibility of constructing a compositionally tuned 0.94-μm laser. Spectroscopic results on this analysis are presented. A laser rod of Nd:Y3Ga1.35Al3.65O12 was made to lase at 0.94465 μm and its performance characterized. This represents the first such laser demonstration on the 4F3/2→4I9/2 laser transition in Nd:YGAG. Improved optical quality and the use of compositional variations of the YGAG structure is expected to improve the laser performance as these materials are more fully developed.

Phonon effects on sharp luminescence lines of Nd3+ in Gd3Sc2Ga3O12 garnet (GSGG)

Abstract The widths, positions and shapes of sharp luminescence lines of the Nd3+ ion in GSGG:Cr3+, Nd3+ were measured carefully from 78 to 600 K. The sharp lines studied correspond to the R2 → Y1, R2 → Y1, R2 → Y3, R1 → Y2, R2 → Y6, R1 → Y6 and R1 → Z5 transitions. All the lines shift to the red with increasing temperature except for the R1 → Z5 line which shifts to the blue. The temperature dependence of line widths and line shifts is explained in terms of an ion-phonon interaction as a perturbation and of a Debye phonon distribution. The Debye temperature is treated as an adjustable parameter to get the best fit to the experiment data. The line widths are related to Raman scattering of phonons, direct phonon processes and statistical local strain of the crystal. The line shifts are due to the stationary effect of the ion-phonon interaction. The Debye temperature of GSGG is estimated to be 500 K through the fittings of the theoretical formulas to the experimental data.

Pulsed laser action in LiYF 4 :Er 3+ , Ho 3+ at 77°K

Pulsed laser action at 77°K has been demonstrated in LiYF 4 :Er3+, Ho3+with an emission wavelength of 2.066 μ. The laser transition is the5 I_{7} \rightarrow 5I 8 in trivalent holmium, and there is evidence of energy transfer from erbium to holmium. The fluorescent lifetime is approximately 20 ms, and the pulsed threshold is 40 joules.

Temperature dependence of spectral linewidths and lineshifts of Nd3+ ions in CaY2Mg2Ge3O12 laser crystal

We have investigated the widths and shifts of the luminescence 4F3/2→4I9/2 line at 940 nm (R1→Z5) and of the 4F3/2→4I11/2 line at 1046 nm (R2→Y1) in the laser crystal CaY2Mg2Ge3O12:Nd3+,Cr3+ from 78 to 300 K. The linewidths are over 20 cm−1. The R2→Y1 line position was found to shift to a longer wavelength and the R1→Z5 to a shorter wavelength with increasing temperature. The results on the thermal line broadening and shifts are compared with the existing theory which uses a simplified ion‐phonon interaction as a perturbation and assumes a Debye phonon distribution for the solid.

Thermal Effects on the Fluorescence Lines of Sm2+ in Crystals

The effects of temperature on the fluorescence lines of Sm2+ in CaF2, SrF2, and BaClF were studied. The results for the first two samples were obtained in the region 10°–100°K. For CaF2 a strong dependence of the linewidth on temperature was found; this width is ∼ 1.7 cm−1 at 15°K and ∼ 40 cm−1 at 95°K. For SrF2, the linewidth is constant and equal to ∼ 2.15 cm−1 up to ∼ 77°K. This difference in behavior is explained qualitatively as due to the fact that in CaF2 the metastable state belongs to the 4f55d configuration and therefore, the electron charge is strongly affected by the thermal perturbations of the environment. We also measured the widths and positions of several fluorescence lines of BaClF:Sm2+ in the 30°–600°K region. The thermal broadening of most of these lines is explained as due to microscopic strains and Raman scattering of phonons, the thermal shifts as due to emission, and absorption of virtual phonons. A Debye model of phonon distribution was used with the same TD for both the lineshift...

Optoenergy storage, stimulated processes in optical amplification with electro-optic ceramic gain media of Nd3+ doped lanthanum lead zirconate titanate

Optical amplification was observed in electro-optic (EO) ceramic plates of neodymium doped lanthanum-modified lead zirconate titanate (Nd3+:PLZT), when the pumping and seeding beams are not overlapped temporarily. This striking feature in the gain measurement and the accompanying slowly trailing-off both seen in the optical amplification as well as in the lasing action are satisfactorily explained by electron releasing from the rich vacancy-based carrier traps in the intrinsically disordered ceramics, i.e., the consecutively optical, thermal stimuli are found responsible for the long persistent optoenergy storage, and consequently the slow response of the gain dynamics. These findings in optical amplification, the slowly trailing-off, and the underlying mechanism have opened a new way of developing novel controllable optical devices. The model thus established could serve as a guide in design and refinement of a new generation of products out of this excellent, well commercialized EO PLZT ceramics family ...