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1.
Tm3+/Yb3+-codoped germanate-niobic (GN) and germanium-bismuth (GB) glasses have been synthesized by conventional melting and quenching method. Intense blue and weak red emissions centered at 477 and 650 nm, corresponding to the transitions 1G4→3H6 and 1G4→3H4, respectively, were observed at room temperature. The possible up-conversion mechanisms are discussed and estimated. GN glass showed a weaker up-conversion emission than GB glass, which is inconsistent with the prediction from the difference of maximum phonon energy between GN and GB glasses. In this paper, Raman spectroscopy was employed to investigate the origin of the difference in up-conversion luminescence in the two glasses. Compared with phonon side-band spectroscopy, Raman spectroscopy extracts more information including both phonon energy and phonon density. For the first time, our results reveal that, besides the maximum phonon energy, the phonon density of host glasses is also an important factor in determining the up-conversion efficiency. 相似文献
2.
Xiaodong Xu Pingxin Song Guoqing Zhou Jun Xu Peizhen Deng 《Solid State Communications》2004,129(11):717-720
Cr4+:YbAG (Cr4+:Yb3Al5O12) crystal with a size up to Φ24 mm×30 mm was grown by the Czochralski method. In the absorption spectrum, there are two absorption bands at 939 and 969 nm, respectively, which are suitable for InGaAs diode laser pumping, and there is an absorption band at 1030 nm, which is suitable for passive Q-switched laser output at 1.03 μm. A broad emission spectrum from 970 to 1100 nm was exhibited from 940 nm wavelength pumping. This crystal is promising as a self-Q-switched laser crystal used for compact, efficient, highly stable, passive self-Q-switched thin chip solid-state lasers. 相似文献
3.
M. H. Niemz 《Applied physics. B, Lasers and optics》1994,58(4):273-281
Experiments on the ablation of dental substance performed with picosecond laser pulses are reported for the first time. A mode locked Nd:YLF oscillator laser was used to generate 25 ps pulses at a wavelength of 1.053µm. These were seeded and amplified to pulse energies up to 1 mJ in a regenerative amplifier laser at repetition rates up to 1 kHz. Very precise cavities were ablated in the enamel of extracted human teeth by mounting the probes onto a computer controlled 3D translation stage. Scanning electron microscopy and dye penetration tests were performed there-after. In contrast to longer pulse durations, picosecond pulses ablate with no signs of thermal damage, if the laser pulses are spatially distributed over the target. Definitions of the physical mechanisms plasma-induced ablation and photodisruption are given. Furthermore, the generated plasma spark has been spectroscopically analyzed. Excitations of calcium and sodium have been observed. From the spectra, the plasma temperature and free electron density could be estimated. By converting part of the laser energy into the second harmonic using a LiNbO3 crystal, a reference amplitude was achieved for the spectra. With this reference signal, a clear distinction could be made between spectra obtained from healthy and caries infected teeth, thus enabling a better control of caries removal in the near future. 相似文献
4.
The airborne transport of particles on a granular surface by the
saltation mechanism is studied through numerical simulation of
particles dragged by turbulent air flow. We calculate the
saturated flux qs and show that its dependence on the wind
strength u* is consistent with several empirical relations
obtained from experimental measurements. We propose and explain
a new relation for fluxes close to the threshold velocity ut,
namely, qs=a(u*-ut)α with α≈2. We
also obtain the distortion of the velocity profile of the wind due to the
drag of the particles and find a novel dynamical
scaling relation. We also obtain a new expression for the dependence of
the height of the saltation layer as function of the strength of the wind. 相似文献
5.
Hongtao Sun Liyan Zhang Junjie Zhang Chunlei Yu Shixun Dai Zhonghong Jiang 《Solid State Communications》2005,133(12):781-784
Infrared-to-visible upconversion fluorescence property of Er3+/Yb3+-codoped novel bismuth-germanium glass under 975 nm LD excitation has been studied. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs. The structure of the bismuth-germanium glass has been investigated by peak-deconvolution of FT-Raman spectrum, and the structural information was obtained from the peak wavenumbers. This novel bismuth-germanium glass with low maximum phonon energy (∼750 cm−1) can be used as potential host material for upconversion lasers. 相似文献
6.
A. Costela I. García-Moreno J. Barroso R. Sastre 《Applied physics. B, Lasers and optics》2000,70(3):367-373
Laser performance of pyrromethene 567 (PM567) dye dissolved in pure poly(methyl methacrylate) homopolymer and its copolymers
with 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 1-vinyl-2-pyrrolidone, 2-phenoxyethyl acrylate, and 2,2,2-trifluoromethyl
methacrylate has been investigated. The chosen monomers were selected to mimic solvents used in a previous study on the photophysical
and lasing properties of PM567 in liquid solution in order to establish correlations between the lasing properties of PM567
in liquid and solid solutions. The vol/vol proportion of the different comonomers in each copolymer formulation was systematically
varied, and the effect of each composition on the lasing properties of PM567 was evaluated. The laser samples were transversely
pumped at 534 nm with 5.5-mJ pulses from a frequency-doubled Q-switched Nd:KGW laser. Lasing efficiencies of up to 30% and
good photostabilities, with a drop of the initial laser output of 20% after 10000 pump pulses in some of the solid samples,
were demonstrated.
Received: 2 June 1999 / Revised version: 18 July 1999 / Published online: 3 November 1999 相似文献
7.
I. Sokólska E. Heumann S. Kück T. Lukasiewicz 《Applied physics. B, Lasers and optics》2000,71(6):893-896
Laser oscillation around 1.6 μm was realised at room temperature for low-doped Er:YVO4 crystals (0.5 at % and 1 at %) as well as for Er(1 at %), Yb(5 at %):YVO4 crystal in continuous-wave mode. The maximum slope of the input–output curve was about 19% (vs. absorbed power) for Er(0.5 at %):YVO4. The laser oscillation was discretely tunable in the spectral range between 1531 and 1604 nm.
Received: 24. August 2000 / Published online: 8 November 2000 相似文献
8.
J. Lu M. Prabhu J. Song C. Li J. Xu K. Ueda A.A. Kaminskii H. Yagi T. Yanagitani 《Applied physics. B, Lasers and optics》2000,71(4):469-473
Optical absorption, emission spectra have been measured for polycrystalline Nd-doped Y3Al5O12 ceramics. Fluorescence lifetimes of 257.6 μs, 237.6 μs, 184.2 μs and 95.6 μs have been obtained for 0.6%, 1%, 2% and 4% neodymium-doped
YAG ceramics, respectively. For the first time, highly efficient laser oscillation at 1064 nm has been obtained with this
kind of ceramics. Slope efficiency of 53% has been achieved on a uncoated 4.8-mm thick 1% Nd:YAG ceramics sample. Optical
to optical conversion efficiency is 47.6%. Laser oscillation has also been obtained with a 2% Nd:YAG ceramics. The optical
properties and laser output results have been compared with that of Nd:YAG single crystal grown by the Czochralski method.
Almost identical results have been achieved including laser experiments results. But fabrication of Nd:YAG ceramics is much
easier compared to the single-crystal growth method. And also large size (now of about 400 mm diameter×5 mm is available)
and high-concentration (>1%) Nd:YAG ceramics can be fabricated. The results show that this kind of Nd:YAG ceramics is a very
good alternative to Nd:YAG single crystal.
Received: 20 April 2000 / Published online: 16 August 2000 相似文献
9.
Efficient Laser-Diode End-Pumped Passively Q-Switched Mode-Locked Yb:LYSO Laser Based on SESAM 下载免费PDF全文
We report an efficient Q-switched laser action based on a semiconductor saturable absorber mirrors (SESAMs) as passively Q-switched laser starter and a Yb:LYSO alloyed crystal as gain material pumped directly by 974nm InGaAs laser diodes. The output pulse duration is measured to be about 7μs, while the average power and the repetition rate of the pulse chain are about 0.92 W and 6.2 kHz, respectively, under 12.5 W absorbed pumping power. The Q-switched mode-locked pulse train is also observed in this setup. The laser performance shows that Yb:LYSO is a promising laser gain medium for laser-diode pumped compact solid-state lasers. 相似文献
10.
S. Canulescu T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2008,93(3):771-778
The mass distributions of the species generated by laser ablation from a La0.6Ca0.4MnO3 target using laser irradiation wavelengths of 193 nm, 266 nm and 308 nm have been investigated with and without a synchronized
gas pulse of N2O. The kinetic energies of the species are measured using an electrostatic deflection energy analyzer, while the mass distributions
of the species were analyzed with a quadrupole mass filter.
In vacuum (pressure 10−7 mbar), the ablation plume consists of metal atoms and ions such as La, Ca, Mn, O, LaO, as well as multiatomic species, e.g.
LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small
amounts.
The interaction of a reactive N2O gas pulse with the ablation plume leads to an increase in plume reactivity, which is desired when thin manganite films are
grown, in order to incorporate the necessary amount of oxygen into the film. The N2O gas pulse appears to have a significant influence on the oxidation of the Mn species in the plume, and on the creation of
negative ions, such as LaO−,O− and O2−. 相似文献