L.E. Bausá

An Introduction to the Optical Spectroscopy of Inorganic Solids: Solé/An Introduction to the Optical Spectroscopy of Inorganic Solids

This practical guide to spectroscopy and inorganic materials meets the demand from academia and the science community for an introductory text that introduces the different optical spectroscopic techniques, used in many laboratories, for material characterisation. * Treats the most basic aspects to be introduced into the field of optical spectroscopy of inorganic materials, enabling a student to interpret simple optical (absorption, reflectivity, emission and scattering) spectra * Contains simple, illustrative examples and solved exercises * Covers the theory, instrumentation and applications of spectroscopy for the characterisation of inorganic materials, including lasers, phosphors and optical materials such as photonics This is an ideal beginners guide for students with some previous knowledge in quantum mechanics and optics, as well as a reference source for professionals or researchers in materials science, especially the growing field of optical materials.

Optical characterization of crystals

A spectroscopic study of ions in and :MgO monocrystals is presented. Polarized absorption and luminescence spectra at low and room temperature allow the identification of the energy levels of the ion in these matrices. The fluorescence decay time has also been investigated and shows an exponential behaviour with a lifetime value of s at 15 K for singly doped . Site selective spectroscopy measurements detect the existence of non-equivalent positions of the which can be related to the presence of in the octahedral site but with slightly different shifts from the regular Li site. Codoping with MgO induces new absorption and emission bands as a consequence of new centres which appear in the matrix due to the presence of ions.

Multimetal rare earth MOFs for lighting and thermometry: tailoring color and optimal temperature range through enhanced disulfobenzoic triplet phosphorescence

New isostructural compounds [Ln7(3,5-DSB)4(OH)9(H2O)15]·4H2O (Ln = Eu, Gd and Tb) (DSB = 3,5-disulfobenzoate), with excellent optical properties, have been obtained and studied. By combining the lanthanide cations with the DSB ligand the formation of a singular heptanuclear [Ln7(OH)9]+12 metallic core secondary building unit (SBU) has been promoted. This core is defined as a bi-capped dicubane SBU, and is a 4-connected node in a bidimensional net with (44·62) topology. The highly efficient emission from the triplet state of the disulfobenzoic ligand in the Gd-MOF and the exponential temperature dependence of ITriplet/ILn = Io exp(−EA/kBT) allow the design of thermometers with different color ranges through the adequate multimetal combination that cover almost the whole visible spectrum and are useful in a wide temperature range (10–300 K) with unprecedented sensitivities up to 32% K−1. The Eu-DSB and Tb-DSB MOFs present an optimum antenna effect, a temperature independent f–f emission temporal decay and, in spite of the close packing of the Ln ions inside the MOF, no concentration quenching. The external efficiency is drastically increased in MOFs with a combination of a few percent of Eu and/or Tb with Gd by means of radiative and non-radiative energy transfers from the Gd ions and Gd connected ligands.

Continuous wave infrared laser action, self-frequency doubling, and tunability of Yb3+:MgO:LiNbO3

The laser performance of the nonlinear Yb3+:MgO:LiNbO3 crystal is assessed under Ti:sapphire laser pumping. Spectral properties related to infrared laser action such as the emission and absorption cross sections have been evaluated. Different crystallographic configurations have been used. Laser oscillation in the near infrared region has been observed along the crystallographic c axis and along the type I phase matching direction for infrared to green generation. High slope efficiency in the infrared region (62%) and the possibility of low laser thresholds (14.7 mW) are demonstrated. By using a birefringent filter, broadband tuning from 1030 to 1070 nm is obtained in this system. In addition, 58 mW of green power by self-frequency doubling of infrared laser emission is achieved, revealing the potential of LiNbO3:MgO as a self-frequency-doubling material.

Rare earth and transition metal ion centers in LiNbO3

Abstract In this work the present state of art about the rare earth and transition metal ion centers phenomenon in LiNbO3 has been analyzed. Particular emphasis has been given to lanthanide trivalent rare earth ions (Pr3+, Nd3+, Eu3+, Dy3+, Ho3+, Er3+, Tm3+ and Yb3+) and to the Cr3+ ion, where most of information has been reported. The structure of these centers is consistent with different off-centered positions of the optically active ions inside the Li+ octahedral site. Stoichiometry and codoping effects on the center distribution are discussed. Finally, possible models to explain the origin of the different centers are discussed.

Phase transition in SrxBa1−xNb2O6 ferroelectric crystals probed by Raman spectroscopy

In this paper the temperature evolution of the main Raman peak at about 630 cm−1 has been studied in order to detect the ferroelectric to paraelectric phase transition in strontium barium niobate (SrxBa1−xNb2O6) crystals with different stoichiometries (x = 0.33, 0.5 and 0.61). Both its peak wavenumber and width have been shown to be strongly dependent on temperature and display clear anomalies around the Curie temperature. The obtained results manifest the usefulness of simple unpolarized Raman spectra to probe the changes in Tc as a result of modifications in the crystal composition.

Characterization of titanium induced optical absorption bands in phosphate glasses

Abstract A detailed study of the optical absorption bands induced by titanium in phosphate glasses has been carried out. Optical absorption, diffuse reflectance and EPR techniques have been used to characterize the centers responsible for these bands, which occur in the near ultraviolet and visible region of the spectrum. Three kinds of centers have been identified: Ti3+ ions in a distorted octahedral environment, which show the 10 Dq value characteristic of these type of centers (17 700 cm−1); Ti4+ ions in octahedral coordination presenting a charge transfer transition in the near UV region; and Ti3+ −Ti4+ mixed complexes, which originate an optical absorption band at 450 nm.

Self-frequency doubling in Yb3+ doped periodically poled LiNbO3:MgO bulk crystal

Continuous-wave laser action from an Yb3+ doped periodically poled LiNbO3:MgO bulk crystal at 1.06 μm is reported. In addition, efficient and stable self-frequency-doubled laser action at 531 nm was obtained by quasiphase matching. Up to 10.5 mW of green output power is obtained from a total laser output power of 58 mW. The experiments were carried out by end pumping with a Ti:sapphire laser, as a surrogate source for a diode laser, at 980 nm. Laser operation was stable at room temperature. The results are compared with those corresponding to single-domain Yb-doped crystals.

Cooperative luminescence in Yb3+ : LiNbO3

Up-converted green luminescence is observed in Yb 3+ : LiNbO 3 under excitation in the near-infrared region. On the basis of the emission and excitation spectra, decay time measurements, and excitation intensity dependence it is concluded that this luminescence is due to a cooperative process consisting on the simultaneous emission of a visible photon by a pair of interacting Yb 3+ ions. The process points out the presence of Yb 3+ pairs within the LiNbO 3 matrix which is also evidenced from the dependence of the cooperative emission on the Yb concentration in the sample.

Optical absorption intensities and fluorescence dynamics of ions in

Optical absorption and fluorescence spectra have been systematically investigated in -doped crystals. The energy position and symmetry character of the Stark levels in the near-infrared region are deduced. The room-temperature absorption line strengths have been experimentally determined and the theory of Judd and Ofelt is used to obtain the radiative lifetimes and branching ratios of the emitting and states. Non-radiative relaxation processes are found to contribute to the transition probabilities of both states. In the case of the multiplets, a multiphonon relaxation process with an effective phonon energy of accounts for the temperature dependence of the lifetime. The -state luminescence shows a non-exponential decay time which indicates the existence of an energy transfer process. This energy transfer process exhibits a Boltzmann-type temperature dependence and is attributed to two-phonon-assisted energy transfer.