Search

We report on the optical characterization of Yb3+ doped BaMgF4 nonlinear fluoride crystal grown by the Czochralski technique. Low temperature absorption spectroscopy reveals that Yb3+ incorporates into the matrix at four well differentiated centers. High resolution site selective experiments have been performed to determine the energy level schemes associated with the major Yb3+ centers detected in the system. The fluorescence decay times recorded at 10 K under selective excitation are analyzed for each Yb3+ center. The spectroscopic behavior of the codoped Yb3+:Na+:BaMgF4 system has been also investigated. Codoping with Na+ eliminates two Yb3+ centers present in the singly doped Yb3+:BaMgF4 crystal. The charge compensation mechanisms and site location for Yb3+ in the fluoride matrix are discussed. [ABSTRACT FROM AUTHOR]

The incorporation of Nd3+ in the ferroelectric fluoride BaMgF4 crystal is investigated for its potential application as self-frequency-converter solid state laser. Low temperature high-resolution optical spectroscopy shows that Nd3+ is located at two well distinguished sites referred as A and B. The whole set of energy levels in the excited 4F3/2, 4I11/2, and ground 4I9/2 states are identified for both Nd3+ sites and their crystallographic location in BaMgF4 lattice is discussed. The radiative lifetime of the 4F3/2 metastable laser level is obtained to be 1430 and 800 μs for site A and B, respectively, and the luminescence quantum efficiency of the 4F3/2 metastable state for the dominant A site is 87%. The possibility of annihilating the contribution of the B site in the optical spectrum is demonstrated by means of the incorporation Na+ into the crystal. [ABSTRACT FROM AUTHOR]

We report on the fabrication and microspectroscopy imaging of femtosecond laser written double-filament based Nd3+:MgO:LiNbO3 optical waveguides. The waveguiding high refractive-index regions are identified by blueshifts of the Nd3+ ion fluorescence lines with no deterioration in the fluorescence efficiency, whereas filamentary low-index regions are identified by both a Nd3+ line redshift and a fluorescence efficiency reduction. The lattice structural micromodifications at the origin of both waveguide formation and Nd3+ fluorescence changes have been investigated by means of confocal micro-Raman experiments. We have found that the direct laser written filaments are mainly constituted by a large density of defects, together with a marked axial compression perpendicular to the filaments (along the optical c-axis). Conversely, the high-index waveguiding regions are characterized by a pronounced anisotropic dilatation of the LiNbO3 lattice xy-planes. [ABSTRACT FROM AUTHOR]

Good quality Ca3Sc2Ge3O12 garnet crystals activated with Yb3+ have been grown by means of the flux growth method and characterized using optical spectroscopy techniques. The low-temperature absorption and emission spectra give evidence of the presence of nonequivalent optical centers, as a consequence of the distribution of the Yb3+ ions in different lattice sites. The effect of codoping with Na+ or Mg2+ on the Yb3+ site distribution has been investigated. The energy-level schemes of the most important centers have been determined on the basis of site-selective spectroscopy experiments. Cooperative luminescence has also been observed and reliably compared with the self-convolution of the NIR luminescence. [ABSTRACT FROM AUTHOR]

Direct electron beam irradiation without static bias has been used to produce stable structures of ferroelectric domain inversion in LiNbO 3 and Nd 3+ doped LiNbO 3 single crystals. Large size cylinder-shaped domain-inverted regions, around 40 μ m diametre and 500 μ m thick, have been achieved in both types of crystals under the same experimental conditions. Raman spectroscopy has been used to analyze the effect of electron irradiation on the domain-inverted regions in the pure and Nd 3 + doped LiNbO 3 single crystals. The results evidence the structural equivalence of the reversed structures and thus, the suitability of this electron bombardment as a poling technique for high quality photonic devices. [ABSTRACT FROM AUTHOR]

Tunable laser action from a diode pumped Nd3+ activated SrxBa1-x(NbO3)2 crystal has been obtained. A wide continuous tuning range of 43 nm in the near infrared region (1050–1093 nm) has been demonstrated due to the broad 4F3/2→4I11/2 emission band present in this system. Simultaneously, 20 nm of tunability in the green region (525–545 nm), as well as 7 nm in the blue one (455–462 nm) have been achieved by tunable self-frequency conversion processes using the quasiphase matching technique, without any angle or thermal tuning of the laser crystal. The results evidence that the system is a reliable candidate for compact tunable coherent devices based on diode pumped Nd3+ active ions, which are of interest in many technological and scientific applications. [ABSTRACT FROM AUTHOR]

We report on the preparation and optical characterization of a two-dimensional multicolor emission arrangement obtained by embedding high refractive-index Er3+ doped CaTiO3 nanoparticles into a Nd3+ doped LiNbO3 crystal substrate prepatterned with an array of microvoids. By controlling the spatial location of the rare earth ions at the micrometer scale, we show the possibility of simultaneous spatial and spectral control of the spontaneous emission in a two-dimensional rare earth optically activated array. The results can be useful for the development of microcomposite rare earth based photonic devices, such as multicolor emission displays or pixelated color structures. [ABSTRACT FROM AUTHOR]

Ferroelectric domain inversion has been obtained in Nd3+ doped lithium niobate by means of direct electron beam writing. The local effects of the polarization inversion on the optical transitions of Nd3+ ions have been studied by low temperature high resolution site selective spectroscopy. Inverted regions present different axial crystal field acting over Nd3+ ions compared with noninverted (original) regions. The results can be interpreted in terms of slight shifts of Nd3+ ions along the ferroelectric c axis within the Li+ octahedrons, as a result of the lattice rearrangement after the domain inversion processes. [ABSTRACT FROM AUTHOR]

Direct intracavity thermal loading measurements have been performed on diode pumped Yb3+ doped LiNbO3:MgO laser crystals. The fractional thermal loading has been found to be strongly dependent on the Yb3+ concentration, decreasing more than 40% when the Yb3+ concentration increases from 0.5 to 2 at. %. From the analysis of the concentration dependence of the fractional thermal loading, the intrinsic fluorescence quantum efficiency (free of radiation trapping) of Yb3+ ions in LiNbO3:MgO crystals has been determined and the role of radiation trapping among Yb3+ ions is discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ferroelectric domain inversion has been obtained in Nd3+ doped lithium niobate by means of direct electron beam writing. The local effects of the polarization inversion on the optical transitions of Nd3+ ions have been studied by low temperature high resolution site selective spectroscopy. Inverted regions present different axial crystal field acting over Nd3+ ions compared with noninverted (original) regions. The results can be interpreted in terms of slight shifts of Nd3+ ions along the ferroelectric c axis within the Li+ octahedrons, as a result of the lattice rearrangement after the domain inversion processes. [ABSTRACT FROM AUTHOR]

The incorporation of Nd3+ in the ferroelectric fluoride BaMgF4 crystal is investigated for its potential application as self-frequency-converter solid state laser. Low temperature high-resolution optical spectroscopy shows that Nd3+ is located at two well distinguished sites referred as A and B. The whole set of energy levels in the excited 4F3/2, 4I11/2, and ground 4I9/2 states are identified for both Nd3+ sites and their crystallographic location in BaMgF4 lattice is discussed. The radiative lifetime of the 4F3/2 metastable laser level is obtained to be 1430 and 800 μs for site A and B, respectively, and the luminescence quantum efficiency of the 4F3/2 metastable state for the dominant A site is 87%. The possibility of annihilating the contribution of the B site in the optical spectrum is demonstrated by means of the incorporation Na+ into the crystal. [ABSTRACT FROM AUTHOR]

Ferroelectric domain patterns are used as templates on which rare earth doped high refractive index nanoparticles activated with trivalent rare earth ions (RE(3+)) are selectively assembled on domain surfaces with a specific polarization. Two-dimensional luminescent heterostructures, with sizes and geometries defined by the ferroelectric patterning are achieved. The process of incorporation and consolidation of the optically active nanoparticles into the alternate domain structures leads to luminescent ring-shaped arrangements with innovative geometries and to a micrometer spatial control of the trivalent rare earth ion emitters. Multicolor emission systems and the possibility of chromatic switching at the micrometer scale among the three different compounds forming the two dimensional structure is demonstrated.

In this Letter we have used the optical pump induced thermal loading to drive Nd(3+) a doped Sr(0,47)Ba(0.53)(Nb)(3))(2) laser crystal during laser operation through its ferroelectric phase transition. We demonstrate that lasing is possible below, at, and above phase transition. For temperatures close to (approximately 105 degrees C) the spatial distribution of laser radiation is remarkably affected. This feature, which leads to a laser gain depression, can be explained in terms of the strong temperature dependence of the thermo-optic coefficient during phase transition. Additionally, the visible radiation generated by intracavity self-frequency doubling disappears when the phase transition is undergone, showing a bistable behavior. The results provide fundamental information on physical parameters along the phase transition and will stimulate further work in the fields of nonlinear optics, optical switching, and data storage.