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Issue 44, 2017
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Design of Yb3+ optical bandwidths by crystallographic modification of disordered calcium niobium gallium laser garnets

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Abstract

{Ca□}3[Nb1−xGax□]2(Ga1−yNby□)3O12-type cubic Ia[3 with combining macron]d garnets (CNGG) have been grown by the Czochralski method, either unmodified or incorporating different crystalline modifiers (Li+ or Mg2+), and Yb3+ as a laser dopant. From nuclear magnetic resonance, single crystal X-ray and powder neutron diffraction studies it is shown that Li+ incorporates exclusively into the 24d tetrahedral site of the host, removing tetrahedral-sited Nb5+ and filling cationic vacancies in this site. A comparison of low temperature (6 K) Yb3+ spectroscopy in crystals with different compositions at the tetrahedral sites and a modeling of energy positions of the 2F7/2(0) and 2F5/2(0′) Yb3+ levels show that the strongest contribution to the Yb3+ optical absorption/emission bandwidth is associated with the electric charge of cations/vacancies occupying the two tetrahedra at the shortest distance (3.12 Å) from the central 24c dodecahedral Yb3+. Cationic disorder over the remaining four tetrahedral, octahedral and dodecahedral sites also contributes to the Yb3+ bandwidth but to a lesser extent. To obtain the largest Yb3+ bandwidth, the two nearest tetrahedra must contain cations/vacancies with electric charges as different as possible. Although the decrease in the concentration of vacancies at tetrahedral sites associated with Li+ incorporation induces some reduction of the Yb3+ optical bandwidth with regard to the unmodified Yb:CNGG crystal, Li+ incorporation along with the use of high purity precursors yields crystals with less coloration, longer Yb3+ lifetime, and slightly larger thermal conductivity, which favors laser operation performance.

Graphical abstract: Design of Yb3+ optical bandwidths by crystallographic modification of disordered calcium niobium gallium laser garnets

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Publication details

The article was received on 20 Jun 2017, accepted on 13 Oct 2017 and first published on 16 Oct 2017


Article type: Paper
DOI: 10.1039/C7TC02760E
Citation: J. Mater. Chem. C, 2017,5, 11481-11495
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    Design of Yb3+ optical bandwidths by crystallographic modification of disordered calcium niobium gallium laser garnets

    M. D. Serrano, J. O. Álvarez-Pérez, C. Zaldo, J. Sanz, I. Sobrados, J. A. Alonso, C. Cascales, M. T. Fernández-Díaz and A. Jezowski, J. Mater. Chem. C, 2017, 5, 11481
    DOI: 10.1039/C7TC02760E

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