Two dimensional ferroelectric domain patterns in Yb3+ optically active LiNbO3 fabricated by direct electron beam writing

The following article appeared in Applied Physics Letters 102.4 (2013): 042910 and may be found at http://scitation.aip.org/content/aip/journal/apl/102/4/10.1063/1.4790149We report on highly controllable ferroelectric domain inversion in Yb 3+ doped LiNbO3 laser crystal. The ferroelectric domain patterns are fabricated by direct electron beam writing without any previous masking process. Square lattices of inverted domains with diameters and distance between domains as low as 1 μm are demonstrated. The lateral growth of the inverted domains is analyzed as a function of the applied charge and the threshold values for domains in the 1-10 μm length scale are determined. Spatially resolved low temperature fluorescence spectroscopy and non-collinear second harmonic generation experiments are also employed to evaluate the optical properties of the system.This work has been supported by Spanish Government under Project No. MAT2010-17443 and Comunidad de Madrid under Grant No. S2009/1756

Plasmon enhanced energy-transfer up-conversion in Yb3+-Er3+ co-doped LiNbO3 crystal

We have analyzed the effect of linear chains of metallic Ag nanoparticles on the optical properties of a periodically poled Yb 3+ -Er 3+ co-doped LiNbO 3 crystal. By exploiting the broad plasmonic response supported by linear chains of strongly coupled Ag nanoparticles, we demonstrate a 50% of enhancement of the up-converted Er 3+ emission under excitation in the f-f transition of Yb 3+ ions. The observed intensification is explained in terms of the broad plasmonic spectral response supported by the Ag chains, which overlaps both the Er 3+ visible emissions and the Yb 3+ absorption band, and the two-photon character of the Yb 3+ → Er 3+ energy-transfer up-conversion process. The results are of interest for applications involving luminescence up-conversion such as sensing, solar energy conversion, biological imaging or solid-state nanolasersThis work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under project MAT2013- 43301-R and Comunidad de Madrid under grant S2013/MIT-274

Plasmon assisted Nd3+-based solid-state nanolaser

Solid-state lasers constitute essential tools in a variety of scientific and technological areas, being available in many different designs. However, although nanolasing has been successfully achieved for dyes and semiconductor gain media associated with plasmonic structures, the operation of solid-state lasers beyond the diffraction limit has not been reported yet. Here, we demonstrate room temperature laser action with subwavelength confinement in a Nd3+-based solid-state laser by means of the localized surface plasmon resonances supported by chains of metallic nanoparticles. We show a 50% reduction of the pump power at threshold and a remarkable 15-fold improvement of the slope efficiency with respect to the bulk laser operation. The results can be extended to the large diversity of solid-state lasers with the subsequent impact on their applicationsThis work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under projects MAT2013-43301-R and FIS2013-41184-P and Comunidad de Madrid under grant S2013/MIT-2740

Narrow inhomogeneous and homogeneous optical linewidths in a rare earth doped transparent ceramic

Inhomogeneous and homogeneous linewidth are reported in a Eu3+ doped transparent Y2O3 ceramic for the 7F 0-5D0 transition, using high-resolution coherent spectroscopy. The 8.7-GHz inhomogeneous linewidth is close to that of single crystals, as is the 59-kHz homogeneous linewidth at 3 K (T2 = 5.4 μs). The homogeneous linewidth exhibits a temperature dependence that is typical of a crystalline environment, and additional dephasing observed in the ceramic is attributed to magnetic impurities or defects introduced during the synthesis process. The absence of Eu3+segregation at the grain boundaries, evidenced through confocal microfluorescence, further indicates that the majority of Eu3+ions in the ceramic experience an environment comparable to a single crystal. The obtained results suggest that ceramic materials can be competitive with single crystals for applications in quantum information and spectral hole burning devices, beyond their current applications in lasers and scintillatorsThis work was supported by National Science Foundation under award No. PHY-1212462, the European Union FP7 project QuRep (247743), the Spanish Ministry of Economy and Competitiveness (MAT2010-17443) and Comunidad de Madrid (S-2009/MAT-1756

0.85 and 1.54 µm emissions of CaF2:Er3+ layers grown by molecular beam epitaxy

Molecular beam epitaxy of CaF2 monocrystalline layers Er3+ doped up to a concentration of 50 mol% is demonstrated on CaF2 substrates. Separated effusion cells containing CaF2 and ErF3 have been used. The photoluminescence spectra of these thin layers exhibit emissions from centers which were found to correspond to those already reported for CaF2 : Er3+ bulk crystals. The influence of growth temperature and Er concentration on the spectroscopic properties of these layers was investigated. The 1.54 µm emission of interest was shown to behave as aggregate centers, and the integrated luminescence was only quenched for concentrations higher than 35 mol%. The trends observed evidence that molecular beam epitaxy is a powerful technique for growing thin Er-doped fluoride layers

VUV–UV 5d–4f interconfigurational transitions of Nd3+Nd^3+ in BaMgF4BaMgF_4 ferroelectric crystals

BaMgF4 single crystals doped with Nd3+ are of great interest as possible active media for VUV–UV and mid-IR all solid-state lasers. The luminescence spectroscopy and the excited state dynamics of these crystals are investigated for the first time upon VUV excitation using synchrotron radiation. The material shows fast Nd3+ 5d–4f emission upon direct VUV excitation into Nd3+ 5d levels. The decay kinetics of the Nd3+ 5d–4f emission in this host lattice upon direct VUV excitation of 5d levels is characterized by a lifetime of about 14 ns with no significant rise after the excitation pulse. No significant temperature dependence of the lifetime is observed within the range 8–300 K

VUV–UV 5d–4f interconfigurational transitions of Nd3+Nd^3+ in BaMgF4BaMgF_4 ferroelectric crystals

BaMgF4 single crystals doped with Nd3+ are of great interest as possible active media for VUV–UV and mid-IR all solid-state lasers. The luminescence spectroscopy and the excited state dynamics of these crystals are investigated for the first time upon VUV excitation using synchrotron radiation. The material shows fast Nd3+ 5d–4f emission upon direct VUV excitation into Nd3+ 5d levels. The decay kinetics of the Nd3+ 5d–4f emission in this host lattice upon direct VUV excitation of 5d levels is characterized by a lifetime of about 14 ns with no significant rise after the excitation pulse. No significant temperature dependence of the lifetime is observed within the range 8–300 K

Site location and crystal field of Nd3+ ions in congruent strontium barium niobate

The site location of Nd3+ ions in congruent strontium barium niobate (Sr0.6Ba0.4Nb2O6) has been systematically investigated by means of low-temperature optical and electron paramagnetic resonance spectroscopies. The experimental results obtained by these complementary techniques clearly indicate that Nd3+ ions are mainly located in only one of the four available cationic sites, the A2 sites, and preserving the C-s local symmetry of these host cation sites. The energy levels and g-factor value experimentally obtained by both techniques have been used to calculate the crystal field parameters for the Nd3+ ions in this A2 cationic site