Sol-gel synthesis of Yb-doped NaLu(WO4)2 films

AbstractDense and (001)-textured thin films with composition NaLu1−xY bx(WO4)2 (x=0.01–0.5) have been prepared by multiple spincoating deposition of sol-gel synthesized solutions, followed by a sintering thermal annealing. Films with thickness above 1 μm are transparent and have photoluminescence properties similar to those of isostructural single crystals. The role of Yb composition, film thickness and purity of the raw Y b2O3 used on the Y b3+ fluorescence efficiency are discussed in relation to the application of the films as diode laser pumped solid-state laser media

Laser floating zone growth of Yb, or Nd, doped (Lu0.3Gd0.7)2SiO5 oxyorthosilicate single-crystal rods with efficient laser performance

Disordered crystals are being presently developed to enlarge the fluorescence bandwidth of trivalent lanthanides incorporated for generation of ultrashort (femtosecond) laser pulses in mode-locked oscillators and amplifiers, but crystal disorder induces a reduction of thermal conductivity which hampers the uniform crystal cooling after growth, leading to internal stresses. This is particularly remarkable when using the Laser Floating Zone (LFZ) growth technique; thus so far laser operation has been obtained only for LFZ-grown crystals with high thermal conductivity (κ ≥ 10 W m−1 °C−1) but without disorder, i.e. YAG, Y2O3 or REVO4. To overcome this limitation we present the LFZ growth of (Lu0.351Gd0.630Yb0.019)2SiO5 and (Lu0.307Gd0.612Nd0.081)2SiO5 refractory (melting point ≈ 1950 °C) oxyorthosilicate single-crystal rods with dimensions suitable for high power diode laser pumping, despite these crystals having medium/low thermal conductivity, κ < 4 W m−1 °C−1. Rods with ≈10 mm length and ≈1.75 mm diameter were grown in air under a CO2 laser at 10 mm h−1. X-ray diffraction analyses confirm the monoclinic C2/c structure of the obtained crystals. For the chosen ≈0.3Lu/0.7Gd ratio some of the crystals are transparent and free of macro-defects. The continuous wave laser performance of Yb3+ and Nd3+ incorporated ions is demonstrated under Ti-sapphire laser pumping in an astigmatism compensated Z-shaped optical cavity. The laser performance of these LFZ oxyorthosilicates is found to be comparable to that reported in Czochralski (Cz) grown crystals. The faster pulling rate (almost one order of magnitude larger for LFZ than for Cz), the high crystal composition purity, and the absence of crucible or atmosphere control make the LFZ technique a low cost alternative for the present needs of diode laser pumped mode-locked medium/high power laser oscillators.This work is funded by FEDER funds (COMPETE 2020 Programme), by national funds through FCT – Portuguese Foundation for Science and Technology (UID/CTM/50025/2019) as well as by Ministerio de Ciencia Innovación y Universidades (RTI2018-094859-B-I00, also FEDER co-fund) of Spain. F. Rey-García acknowledges European Union (H2020-FET-OPEN/0426), Xunta de Galicia (ED431E 2018/08) and FCT (SFRH/BPD/108581/2015) projects.Peer reviewe

Optical emission properties of Nd3+ in NaBi(WO4)(2) single crystal

Room temperature optical absorption measurements of Nd3+ in NaBi(WO4)2 single crystals grown by the Czochralski method have been used to calculate the following Judd-Ofelt intensity parameters: Omega2 =30.9 × 10-20 cm2, Omega4 = 12.0 × 10-20 cm2 and Omega6 =9.3 × 10-20 cm2. Using these parameters the emission properties of Nd3+ in this host have been estimated with particular attention to the 4F3/2 energy level responsible for stimulated emission channels. The experimental branching ratios of this level are obtained from photoluminescence and agree with those calculated using the above Omegak parameters. The 4F3/2 emission has negligible non-radiative intrinsic losses and the 10 K lifetime at low Nd concentration, 0.9× 1018 cm-3, is tauexp= 143 mus. Even at 300 K and for a much higher Nd concentration, 4.0× 1019 cm-3, non-radiative losses are moderate, giving a quantum efficiency eta ap 0.85. The 4F3/2 emissions show a strongly polarized character. The largest emission cross-section occurs at lambda =1060.9 nm for the 4F3/2 rarr4I11/2 laser channel with a pi-polarized character, sigmaEMI= 16× 10-20 cm2.This work is supported by the Ministerio de Ciencia y Tecnologıa(MCy T) in Spain, under project the MAT2002-0463-C05-05. V. Volkov acknowledges support by a NATO grant. A. Mendez-Blas is supported by CONACYT (Mexico), grant No. 128118.Peer reviewe

Growth of (Pb,La)TiO3 and ZnO thin films on (100)InP by PulseD Laser deposition

[ES] Se ha estudiado el proceso de depósito mediante ablación con láser de láminas delgadas de PbTiO3 modificado con La (PLT) y ZnO sobre (100)InP. Para el PLT se han depositado láminas intermedias de óxidos dieléctricos (CeO2, ZrO2, SrO, YSZ, MgO, y SrTiO3) necesarias para la protección de la superficie del substrato. En cada caso se han establecido las condiciones experimentales (presión de oxígeno, temperatura del substrato, densidad de energía del pulso láser y limpieza de la superficie del substrato) necesarias para obtener láminas cristalinas con orientación preferente. En la heteroestructura PLT/YSZ/(100)InP se estudian los cambios de composición y morfología a lo largo del perfil de la heteroestructura, a fin de investigar los procesos involucrados en el crecimiento de estos óxidos sobre el (100)InP.[EN] The oriented growth of PbLaTiO3 (PLT) and ZnO thin films on (100)InP has been studied, including the influence of buffer oxide layers (CeO2, ZrO2, SrO, YSZ, MgO, and SrTiO3) on the final texture of PLT film obtained. In each case the oxygen pressure, substrate temperature, energy fluence and substrate surface conditions required to obtain a crystalline and preferentially oriented phase have been established. The composition and morphological changes related to the PLT/YSZ/(100)InP heterostructure profile have been studied in order to investigate the processes involved in the growth of these oxides on (100)InP.Este trabajo ha sido financiado por CICyT y por la Comunidad Autónoma de Madrid con de los proyectos TIC96- 1039 y 07T/0032/1997 respectivamente. E. V. está subvencionado por la Agencia Española de Cooperación Internacional a través de una beca doctoral Mutis.Peer reviewe

Emission cross sections and spectroscopy of Ho3+ laser channels in KGd(WO4)2 single crystal

The spectroscopic properties of Ho3+ laser channels in KGd(WO4)2 crystals have been investigated using optical absorption, photoluminescence, and lifetime measurements. The radiative lifetimes of Ho3+ have been calculated through a Judd-Ofelt (JO) formalism using 300-K optical absorption results. The JO parameters obtained were Ω2=15.35×10-20 cm2, Ω 4=3.79×10-20 cm2, Ω6 =1.69×10-20 cm2. The 7-300-K lifetimes obtained in diluted (8·1018 cm-3) KGW:0.1% Ho samples are: τ(5F3)=0.9 μs, τ( 5S2)=19-3.6 μs, and τ(5F5 )=1.1 μs. For Ho concentrations below 1.5×1020 cm-3, multiphonon emission is the main source of non radiative losses, and the temperature independent multiphonon probability in KGW is found to follow the energy gap law τph -1(0)=βexp(-αΔE), where β=1.4×10-7 s-1, and α=1.4×103 cm. Above this holmium concentration, energy transfer between Ho impurities also contributes to the losses. The spectral distributions of the Ho3+ emission cross section σEM for several laser channels are calculated in σ- and π-polarized configurations. The peak a σEM values achieved for transitions to the 5I8 level are ≈2×10-20 cm2 in the σ-polarized configuration, and three main lasing peaks at 2.02, 2.05, and 2.07 μm are envisaged inside the 5I7→5I8 channel.This work was supported by Comisión Interministerial de Ciencia y Tecnología under Projects MAT99-1077 and 2FD97-0912.Peer reviewe

Matriz de diodos electroluminiscentes orgánicos emisores en el infrarrojo cercano (1.54 μm) basados en complejos de erbio fabricados por métodos de bajo coste

[EN]: Solution processed 1.54 μm near infrared organic light-emitting diodes (NIR-OLED) based on novel Er(III) complexes, having the general formula[Er(β-diketonate) 3 (N,Ndonor)], have been manufactured by cost-effective methods and their properties studied. 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (Htfnb or Hnta) or 1,1,1-trifuoro-5,5-dimethyl-2,4-hexanedione (Htpm) are the fluorinated β-diketonate primary sensitizers, and 2,2'-bipyridine (bipy) or 5-nitro-1,10-phenanthroline (5NO2phen) act as N,N-donors. The simple structure of the diodes is glass/indium-tin oxide (ITO)/poly (3,4-ethylenedioxythiophene)-poly(styrene sulfonate)/[Er-complex]/Ca/Al. The resulting electroluminescence corresponds with the 4I13/2→4I15/2 Er(III) emission at 1.54 μm and no visible emission is observed. Photophysical characterization proves that, upon organic ligand excitation by UV light, the luminescence from the ligands is totally quenched in favour of 4I13/2→4I15/2 Er(III) emission, confirming a complete resonant energy transfer from the ligands to the Er(III) ion, analogous to that observed in the electroluminescence emission. We present a fabrication method that avoids any photolithographic or mask step. The reported results showa simple way to obtain large area NIR-OLEDs by cost-effective methods. © Sociedad Española de Óptica.[ES]: Se han fabricado y caracterizado diodos orgánicos emisores de luz en el infrarrojo cercano (NIR-OLED) procesados desde solución, basados en nuevos complejos de Erbio (III) con fórmula general [Er(β-d)3(N,N-donor)] utilizando métodos de bajo coste. Los ligandos primarios son β-dicetonatos fluorados 4,4,4-trifluoro-1-(2-naftil)-1,3-butanodiona (Htfnb o Hnta) o 1,1,1-trifluoro -5,5-dimetil-2,4-hexanodiona (Htpm) y los ligandos secundarios 2,2’-bipiridina (bipy) o 5-nitro-1,10-fenantrolina (5NO2phen) actúan como bases de Lewis. La estructura del diodo es vidrio/óxido indio-estaño (ITO)/poli (3,4-etilendioxitiofeno)-poli (estireno sulfonato)/complejo de Er(III)/Calcio/Aluminio. La electroluminiscencia resultante corresponde con la emisión de la transición 4I13/2→4I15/2 del Er(III) a 1.5 μm sin que se observe emisión alguna en el visible. La caracterización fotofísica muestra que, bajo excitación con luz UV, se produce un apagamiento de la emisión de los ligandos acompañado por una emisión en el NIR del Er(III) análoga a la obtenida por excitación eléctrica, confirmando de este modo la transferencia completa de energía desde los ligandos al ion Er(III). Presentamos un método de fabricación que evita cualquier paso fotolitográfico con máscara. Los resultados reportados muestran un camino sencillo para obtener diodos emisores de luz en el infrarrojo cercano utilizando métodos de bajo coste.P. Martín-Ramos thanks the Spanish Ministry of Education and Santander Universidades JPI_2013 for their financial support. Comunidad Autónoma de Madrid under projects S2009/MAT-1756 and S2009/ESP-1781. Spanish Ministerio de Economía y Competitividad (MINECO) under projects MAT2012-37276-C03-03 and TEC2011-13635-E are gratefully acknowledged by C. Coya. CEMDRX group is grateful to the Fundação para Ciência e a Tecnologia (FCT) under grant PTDC/FIS/102284/2008. UVA group acknowledges financial support of Junta de Castilla y León through project VA300A12-1.Peer Reviewe

Surface-relief micropatterning of zinc oxide substrates by micromolding pulsed-laser-deposited films

Surface-relief patterning of semiconductor surfaces has become a very active research topic during the last few years. This growing interest is related to the wide range of technological applications of patterned semiconductor surfaces, with particular emphasis on photovoltaic technology. In this work, we show a straightforward, cost-effective and non-hard lithographic approach for transferring surface-relief micropatterns on ZnO surfaces. The method is based on direct micromolding of pulsed-laser deposited ZnO films using surface-modified metallic micromolds. In contrast to those obtained by photolithographic techniques, direct micromolded ZnO surfaces are characterized by very low roughness values on the transferred relief patterns.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Tunable continuous wave and femtosecond mode-locked Yb3+ laser operation in NaLu(WO4)2

7 pages, 13 figures, 3 tables.-- PACS: 42.55.Rz; 42.60.By; 42.60.FcContinuous wave and femtosecond mode-locked laser operation of Yb3+ in the tetragonal NaLu(WO4)2 crystal host is demonstrated by pumping with a Ti:sapphire laser. Pumping with 1.8 W at 974 nm, a maximum output power of 650 mW was achieved at 1029.6 nm. The slope efficiency was in excess of 60%. The laser performance was similar for the two polarizations. By inserting a birefringent filter the output wavelength was tunable from 1010 to 1055 nm. Pulses as short as 90 fs with an average power of 50 mW were generated by passive mode locking at a repetition rate of 95 MHz. These attractive laser properties of NaLu1−xYbx(WO4)2 are related to the inhomogeneous broadening of the Yb3+ spectral features resulting from the local disorder of the host crystal. We report the spectroscopic properties of Yb3+ in the 5–300 K temperature range and the optical properties of the host at room temperature.This work was supported by Projects Nos. NMP3-CT- 2003-505580 (EU), MAT2004-21113E, and MAT2005-6354- C03-01 (Spain). A.G. (FPU2003-018), X.H. (JC12006-4015-2459) and X.M. (EX2004-1294) are supported by grants from the Spanish government. X.M. additionally acknowledges support from the European Science Foundation.Peer reviewe

Tunable continuous wave and femtosecond mode-locked Yb3+ laser operation in NaLu(WO4)2

7 pages, 13 figures, 3 tables.-- PACS: 42.55.Rz; 42.60.By; 42.60.FcContinuous wave and femtosecond mode-locked laser operation of Yb3+ in the tetragonal NaLu(WO4)2 crystal host is demonstrated by pumping with a Ti:sapphire laser. Pumping with 1.8 W at 974 nm, a maximum output power of 650 mW was achieved at 1029.6 nm. The slope efficiency was in excess of 60%. The laser performance was similar for the two polarizations. By inserting a birefringent filter the output wavelength was tunable from 1010 to 1055 nm. Pulses as short as 90 fs with an average power of 50 mW were generated by passive mode locking at a repetition rate of 95 MHz. These attractive laser properties of NaLu1−xYbx(WO4)2 are related to the inhomogeneous broadening of the Yb3+ spectral features resulting from the local disorder of the host crystal. We report the spectroscopic properties of Yb3+ in the 5–300 K temperature range and the optical properties of the host at room temperature.This work was supported by Projects Nos. NMP3-CT- 2003-505580 (EU), MAT2004-21113E, and MAT2005-6354- C03-01 (Spain). A.G. (FPU2003-018), X.H. (JC12006-4015-2459) and X.M. (EX2004-1294) are supported by grants from the Spanish government. X.M. additionally acknowledges support from the European Science Foundation.Peer reviewe