Nagoya-shi, Japan
Nagoya-shi, Japan

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Nakayama S.,Niihama National College of Technology | Ikesue A.,World Laboratory Co. | Higuchi Y.,Honda Research and Development Co. | Sugawara M.,Honda Research and Development Co. | Sakamoto M.,Yamagata University
Journal of the European Ceramic Society | Year: 2013

A hexagonal apatite-type La 9.33Si 6O 26 single crystal as an oxide ionic conductor has been successfully prepared by a method which is based on the single crystallization of the sintered polycrystalline La 9.33Si 6O 26 ceramic on the surface of seed single crystal without their melt. The anisotropy in its conductivity was observed: conductivity component parallel to the c-axis was ca. 100 times higher than the perpendicular component. © 2012 Elsevier Ltd.


Lupei A.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Lupei V.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Gheorghe C.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co.
Romanian Reports in Physics | Year: 2011

An analysis of the high resolution optical spectra (at 10 or 300 K) of Sm3+ in YAG transparent ceramics is presented. The peculiarities of the spectra in ceramics are outlined. Accurate data for the application of Sm3+: YAG ceramic to suppress parasitic oscillations in high power Nd: YAG ceramic composite lasers are obtained.


Lupei V.,National Institute for Laser, Plasma and Radiation Physics | Lupei A.,National Institute for Laser, Plasma and Radiation Physics | Gheorghe C.,National Institute for Laser, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co.
Optical Materials Express | Year: 2016

High resolution spectroscopy brings new data on the spectroscopic and energy transfer properties of the transparent (Cr,Nd):YAG ceramics. The role of joint superexchange and electric dipole interactions in the Cr-to-Nd energy transfer is evidenced and the calculated emission quantum efficiency is essentially determined by the Nd concentration, 52% for 1 at.%Nd and 77% for 2 at.%Nd. The implication of Cr and Nd concentrations on the laser emission and heat generation under broad-band pumping is discussed. © 2016 Optical Society of America.


Lupei A.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Lupei V.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co. | Gheorghe C.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Journal of the Optical Society of America B: Optical Physics | Year: 2010

The Nd3+→Yb3+ energy transfer spectral characteristics in (Nd,Yb):Y2O3 ceramics and the relevant spectral and emission decay data on single-doped (especially temperature effects) and codoped samples are presented. The transfer efficiencies depend strongly on Yb3+ content, attaining ∼98% for Nd1 at.%-Yb5 at.% at 300 K. The resonant Nd3+→Yb3+ energy transfer ( 4F3/2(Nd), 2F7/2(Yb))→( 4I9/2(Nd), 2F5/2(Yb)), involving Nd3+ in C2 sites and Yb3+ in C2 and C3i sites, is dominated by a dipole-dipole interaction with a microparameter CDA,Nd-Yb≈1×10?38 cm6 s?1 at 300 K. The possibility of using this system for Nd-sensitized Yb3+ laser emission from room-to-cryogenic temperatures is discussed. © 2010 Optical Society of America.


Lupei A.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Lupei V.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co. | Gheorghe C.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Hau S.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Optical Materials | Year: 2010

In the attempt to obtain new efficient laser systems, the Nd → Yb energy transfer characteristics in Y2O3 transparent ceramics were investigated. The spectral characteristics that assure the efficient resonant Nd3+ → Yb3+ energy transfer are presented, especially the overlap integral of the Nd3+ 4F3/2 → 4I9/2 emission with the Yb3+ 2F7/2 → 2F5/2 absorption in (Nd, Yb):Y2O3. The static spectral data reveal that the Nd3+ → Yb3+ energy transfer shows: a strong dependence on Yb3+ content (less on Nd3+), a small variation with temperature and the implication of both Yb3+ sites in transfer, though only Nd3+ in C2 are active. From the analysis of Nd3+ 4F3/2 emission decays in double doped samples it is concluded that the Nd → Yb transfer for Nd ∼1 at.% is of direct type, through the dipole-dipole interaction with global energy transfer microparameter ∼CDA,Nd-Yb ≈ 1 × 10-38 cm6 s-1 and transfer efficiencies up to 98% for rather low (∼5 at.%) Yb3+ content. © 2010 Elsevier B.V. All rights reserved.


Lupei A.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Lupei V.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Gheorghe C.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co. | Enculescu M.,National Institute of Materials Physics Bucharest
Journal of Applied Physics | Year: 2011

The spectroscopic characteristics of Dy3+ in YAG (Y 3Al5O12) transparent ceramics prepared by solid state synthesis were investigated, with special attention to the visible (yellow, blue) emissions that could be pumped directly by the new developed blue-violet or near UV laser diodes. The absorption and emission spectra, recorded at different temperatures from 10 to 300 K, were analyzed and relevant new parameters, improved energy level scheme, temperature effects, intensity parameters based on Judd-Ofelt theory and radiative transition rates, branching ratios, etc., were estimated and the data are compared with previous reports on garnet single crystals. The potential of the Dy3+: YAG transparent ceramics for yellow or blue laser emission is discussed. © 2011 American Institute of Physics.


Newburgh G.A.,U.S. Army | Word-Daniels A.,Princeton University | Michael A.,U.S. Army | Merkle L.D.,U.S. Army | And 2 more authors.
Optics Express | Year: 2011

We report what is believed to be the first laser operation based on Ho 3+-doped Y2O3. The Ho3+:Y 2O3 ceramic was resonantly diode-pumped at ∼1.93 μm to produce up to 2.5 W of continuous wave (CW) output power at ∼2.12 μm. The laser had a slope efficiency of ∼35% with respect to absorbed power and a beam propagation factor of M2 ∼1.1. We have measured the absorption and stimulated emission cross sections of Ho3+:Y 2O3 at 77 K and 300 K and present the calculated gain cross section spectrum at 77 K for different excited state inversion levels. © 2011 Optical Society of America.


Lupei V.,National Institute for Laser, Plasma and Radiation Physics | Lupei A.,National Institute for Laser, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co.
Spectroscopy Letters | Year: 2010

This article presents new data on multicenter structure of the optical spectra and of emission dynamics of the doping ions in various types of crystalline and polycrystalline cubic laser materials (garnets, sesquioxides). It is inferred that the satellite structure of the active ions is induced by crystal field perturbations inside the near neighbor associations of the active ion with specific defects of the host lattice (P-type satellites independent on doping concentration) or with other active ions (M-type satellites dependent on doping concentration). Such satellite structures are described for various rare earth ions; including Nd3+, Pr3+, Er3+. In case of the garnet crystals, both types of satellites are present, and the satellites P can be connected with departures from stoichiometry; in garnet ceramics, they are much less intense. In contrast, the structures of M satellites are similar in garnet crystals and ceramics, indicating similar distribution of the doping ions in the host matrix. The luminescence spectra of these materials are influenced by the emission quantum efficiency of the various centers. In the case of sensitized materials, the mutual crystal field perturbations could modify the absorption spectra on both the sensitizer ions. In the case of materials with charge compensation, the electric charge disordering determined by the process of compensation strongly influences the optical spectra of the doping ions and their distribution. The relation between the global spectroscopic properties and those measured by microscopic methods is also considered. The connection between the fabrication process, structure, spectroscopic, and laser emission properties is shown and it is inferred that the multicenter structure of the spectra, together with emission dynamics, can be an efficient tool for investigating the microstructure of the laser materials, for optimization of laser properties, or for tailoring new laser materials. © Taylor & Francis Group, LLC.


Epicier T.,University Claude Bernard Lyon 1 | Boulon G.,Luminescent | Zhao W.,Luminescent | Zhao W.,Anhui University of Science and Technology | And 5 more authors.
Journal of Materials Chemistry | Year: 2012

There is a need to investigate the possible improvements of rare earth ion-doped transparent ceramics in terms of better optical performances for lasers, scintillators and phosphors. Especially, the spatial distribution of the rare earth ions within their host material is important for quenching processes. Results from Transmission Electron Microscopy (TEM, both conventional and high resolution TEM) and EDX (energy dispersive X-ray) quantitative chemical analysis positively show that there is no significant segregation of Yb 3+ ions, the last active rare earth element, in the grain boundaries of Yb 3+-doped YAG and Yb 3+-doped Y 2O 3 polycrystalline ceramics. The large value of the Yb 3+ segregation coefficient (1.09 in YAG ceramic) explains the homogeneity of this distribution, in opposition to the low values of the Ce 3+ and Nd 3+ segregation coefficients, the first active rare earth elements, (0.08 and 0.18 respectively in YAG ceramic), which leads to a strong segregation at grain boundaries. © 2012 The Royal Society of Chemistry.


Gheorghe C.,National Institute for Laser, Plasma and Radiation Physics | Lupei A.,National Institute for Laser, Plasma and Radiation Physics | Lupei V.,National Institute for Laser, Plasma and Radiation Physics | Ikesue A.,World Laboratory Co. | Enculescu M.,National Institute of Materials Physics Bucharest
Optical Materials | Year: 2011

This work is focused on spectral investigations of Tm3+ doped Sc2O3 transparent ceramic as potential material for diode-pumped solid-state laser emitting around 2 μm. In the context of the Judd-Ofelt (J-O) theory a series of spectroscopic parameters such as J-O intensity parameters, oscillator strengths, radiative transitions probabilities, and radiative lifetimes as well as branching ratios are evaluated. The gain cross-sections which lead to an estimation of the probable operating laser wavelength for the 3F4 → 3H6 Tm3+ laser transition were also calculated. © 2010 Elsevier B.V. All rights reserved.

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