Highly efficient diode-pumped 3-μm Er3+:BaY2F8 laser

A systematic investigation on a series of monoclinic Er³⁺ :BaY₂F₈ crystals with different dopant concentrations (C_Er=5%-30%) and crystal orientations was conducted to optimize the laser performance in this new 3-μm laser medium by laser diode pumping. The highest slope efficiency of 32% near the quantum defect (35%) was obtained with a 10% doped Er³⁺:BaY₂F₈ crystal with the orientation (010) and a length of 3.5 mm. A maximum output power of 160 mW was achieved at an absorbed pump power of 550 mW at a wavelength of 970 nm     

Nonlinear optical compression of Er3+-fiber amplified1.5-μm laser diode pulses

Femtosecond optical pulses of 110-200-fs width have been produced using a gain-switched distributed-feedback semiconductor laser followed successively by a linear compression stage and a nonlinear compression stage. Analysis is focused on this last stage where pulses with peak powers corresponding to 10and 12-order solitons are fed at the fiber input end. Experimental results are well described using both the modified nonlinear Schrodinger equation and an accurate intensity and phase model of the gain-switched laser diode. Experiments are shown to be correctly described only if both intrapulse stimulated Raman scattering and third-order dispersion are taken into account. Guidelines are then given to optimize the nonlinear fiber compression using laser diodes and fiber amplifiers. The influence of the third-order dispersion in the fiber compressor is first evaluated. Second, the nonlinear self-phase modulation induced in the fiber amplifier is studied. It is shown to be the main factor limiting any further pulse shortening with this technique     

二氧化锰结构参数与嵌Li+和H+的行为

H+与Li+在γ-MnO2中的嵌脱行为是由其结构(缺陷)参数决定的.不同晶型的二氧化锰或晶型相同而制备条件不同的二氧化锰,具有不同的结构参数.介绍了有利于嵌脱H+和Li+的γ-MnO2结构(缺陷)参数,结构参数与γ-MnO2在碱液中的还原机理,以及如何控制制备条件,使之具有某种结构参数等.     

1.047-μm Yb:Sr5(PO4)3F energystorage optical amplifier

The pumping and gain properties of Yb³⁺-doped Sr₅ (PO₄)₃F (Yb:S-FAP) are reported. Using a tunable, free running 900-nm Cr:LiSAF oscillator as a pump source for a Yb:S-FAP rod, the saturation fluence for pumping was measured to be 2.2 J/cm² based on either the spatial, temporal, or energy transmission properties of the Yb:S-FAP rod. The emission peak of Yb:S-FAP (1047.5 nm in air) is shown to overlap with that of Nd:YLiF₄ (Nd:YLF) to within 0.1 nm, rendering Yb:S-FAP suitable as an effective power amplifier for Nd:YLF oscillators. The small signal gain, under varying pumping conditions, was measured with a cw Nd:YLF probe laser. These measurements implied emission cross sections of 6.0×10^-20 and 1.5×10^-20 cm ² for π and σ polarized light. Respectively, which fall within the error limits of the previously reported values of 7.3×10^-20 and 1.4×10^-20 cm² for π and σ polarized light, obtained from purely spectroscopic techniques. The effects of radiation trapping on the emission lifetime have been quantified and have been shown to lead to emission lifetimes as long as 1.7 ms, for large optically dense crystals. This is substantially larger than the measured intrinsic lifetime of 1.10 ms. Yb:S-FAP crystal boules up to 25×25×175 mm in size, which were grown for the above experiments and were found to have acceptable loss characteristics (<~1%/cm) and adequately large laser damage thresholds at 1064 nm (~20 J/cm² at 3 ns). Overall, diode-pumped Yb:S-FAP amplifiers are anticipated to offer a viable means of amplifying 1.047-μm light, and may be particularly well suited to applications sensitive to overall laser efficiencies, such as inertial confinement fusion energy applications     

Continuous-wave broadly tunable intracavity frequency-doubled Cr4+: forsterite laser

Continuous-wave (CW) power performance of a room-temperature, broadly tunable intracavity frequency-doubled Cr⁴⁺: forsterite laser is described. Intracavity doubling was achieved by using a 2-cm-long periodically poled lithium niobate (PPLN) crystal. At the PPLN crystal temperature of 188°C, orange-red radiation could be obtained between 613 and 655 nm by using gratings with different poling periods. Experimentally measured temperature tuning data of the PPLN crystal was further found to be in very good agreement with theoretical predictions based on temperature-dependent Sellmeier data. With an incident pump power of 6.8 W at 1064 nm, the Cr⁴⁺: forsterite laser produced 245 mW of CW output power at 1260 nm and intracavity doubling yielded 45 mW of second harmonic output at 630 nm     

Ce3+:LiCaAlF6 crystal for high-gain orhigh-peak-power amplification of ultraviolet femtosecond pulses and newpotential ultraviolet gain medium: Ce3+:LiSr0.8Ca0.2AlF6

To develop high-peak-power ultrashort pulse laser systems in the ultraviolet region, a large Ce³⁺:LiCaAlF₆ (Ce:LiCAF) crystal, a tunable ultraviolet laser medium with large saturation fluence and broad gain spectrum width, was grown successfully with a diameter of more than 70 mm. To demonstrate high small signal gain, a four-pass confocal amplifier with 60 dB gain and 54 μJ output energy was constructed. Chirped pulse amplification (CPA) in the ultraviolet region was demonstrated using Ce:LiCAF for higher energy extraction. A modified bow-tie-style four-pass amplifier pumped by 100-mJ 266-nm 10-Hz pulses from a Q-switched Nd:YAG laser had 370-times gain and delivered 6-mJ 290-nm pulses. After dispersion compensation, the output pulses can be compressed down to 115 fs. This is the first ultraviolet, all-solid-state high-peak-power CPA laser system using ultraviolet gain media, and this demonstration shows further scalability of the Ce:LiCAF CPA system. Additionally, a new gain medium, Ce³⁺ :LiSr_0.8Ca_0.2AlF₆, with longer fluorescence lifetime and sufficient gain spectrum width over 18 nm was grown to upgrade this system as a candidate for a final power amplifier gain module     

Comparison of laser-produced plasma target materials for pumpingthe 109-nm Xe2+ Auger laser

We compared cadmium, copper, gold, and zinc targets to stainless steel for laser-produced plasma pumping the Xe²⁺ 109 nm laser. A unique target geometry allowed us to measure the laser output using two materials under identical conditions. Small signal gain coefficients and maximum output powers are presented for each material relative to stainless steel; we observed a ~20% improvement in the gain coefficient and a ~112% improvement in total energy using a cadmium target. This increase probably results from an improved overlap of the laser-produced plasma emission spectrum with the Xe inner shell 4d photoionization cross section, although published data to support this hypothesis are scarce and inconsistent     

The metal-organic chemical vapor deposition growth and propertiesof InAsSb mid-infrared (3-6-μm) lasers and LEDs

We describe the metal-organic chemical vapor deposition (MOCVD) growth of AlAs_1-xSb_x cladding layers and InAsSb-InAs multiple-quantum well (MQW) and InAsSb-InAsP strained-layer superlattice (SLS) active regions for use in mid-infrared emitters. The AlAs_1-xSb_x cladding layers were successfully doped p- or n-type using diethylzinc or tetraethyltin, respectively. By changing the layer thickness and composition of SLSs and MQWs, we have prepared structures with low temperature (<20 K) photoluminescence wavelengths ranging from 3.2 to 6.0 μm. We have made gain-guided injection lasers using undoped p-type AlAs_0.16Sb_0.84 for optical confinement and both strained InAsSb-InAs MQW and InAsSb-InAsP SLS active regions. The lasers and light emitting diodes (LEDs) utilize the semi-metal properties of a GaAsSb(p)-InAs(n) heterojunction as a source for electrons injected into active regions. A multiple-stage LED utilizing this semi-metal injection scheme is reported. Gain-guided, injected lasers with a strained InAsSb-InAs MQW active region operated up to 210 K in pulsed mode with an emission wavelength of 3.8-3.9 μm and a characteristic temperature of 29-40 K. We also present results for both optically pumped and injection lasers with InAsSb-InAsP SLS active regions. The maximum operating temperature of an optically pumped 3.7-μm strained-layer superlattice (SLS) laser was 240 K. An SLS LED emitted at 4.0 μm with 80 μW of power at 300 K     

Comparative Performance of Passively Q-Switched Diode-Pumped Yb 3+-Doped Tungstate and Garnet Lasers Using Cr 4+:YAG Saturable Absorber

We investigated the continuous wave (CW) free-running and repetitive modulation in the kilohertz frequency domain of a passively Q-switched diode-pumped Yb:YAG, Yb:GGG, and Yb:KYW lasers by using Cr⁴⁺:YAG as a saturable absorber. The results presented in this paper are focused on the design of a passively Q-switched Yb-doped garnets or Yb-doped tungstates microlasers. The free-running performance of Yb:YAG, Yb:GGG, Yb:KGW, and Yb:KYW were characterized, and experimental parameters such as gain and loss were evaluated. We carried out a fit between our experimental results and an existing numerical model, which relates the experimental and the physical parameters of the ytterbium diode-pumped system to the minimal threshold pumping power. The best performance among the laser crystals was obtained for Yb:YAG laser. A maximum peak power of ap4.5 kW at an average output power of 1.32 W was extracted with an extraction efficiency of ap25%.     

Cr4+ lasers: present performance and prospects for newhost lattices

Cr-doped lasers, based on forsterite and YAG, provide broadly tunable power in the 1.25-μm and 1.45-μm regions. Performance data on tuning range, pumping, output power, and thermal management for these lasers is reviewed. Potential new crystals for Cr⁴⁺ should have heavy atoms to reduce lattice phonon frequencies, a distorted tetrahedral cage for the Cr⁴⁺ ion, and possibly an octahedral site for Cr³⁺. Possible materials include monticellite and diopside     

Dy2O3掺杂LiDyxMn2-xO4的合成及性能

采用类似溶胶-凝胶法合成稀土金属氧化物Dy2O3掺杂LiDyxMn2-xO4(x=0,0.01,0.02,0.05).通过XRD和恒流充放电测试了稀土金属元素Dy的掺杂对正极材料的结构以及电化学性能的影响.研究结果表明当掺杂量x=0.02时,材料LiDy0.02Mn1.98O4具有较高的初始比容量(109mAh/g)和循环性能,50次循环后,容量保持率为95%.     

Tunable diode laser spectroscopy at 1.6 and 2 μm for detectionof Helicobacter pylori infection using 13C-urea breath test

Tunable diode laser spectroscopy has been applied to diagnosis of Helicobacter pylori by detecting the ¹³CO₂ to isotope ratio in human breath. A number of line pairs in the 1.6- and 2.0-μm band suitable for isotope ratio detection has been investigated in terms of temperature and pressure stability of the detected isotope ratio. Two wavelength modulated diode laser absorption spectrometers (WMS), one in each band, were set up to find the detection limit in isotope abundance difference. Isotope ratio measurements have been performed on ¹³CO₂ enriched gases with isotope ratios calibrated against an isotope ratio mass spectrometer (IRMS). The agreement between the delta values measured with the WMS technique and the IRMS was excellent. Eight breath samples from otherwise healthy volunteers were simultaneously analyzed by IRMS and the present method for possible infection with Helicobacter pylori     

Melt synthesis and characterization of complexed perovskite-oxides in the system of A2+(B+ 2/5B6+ 3/5)O3 - A3+(B+ 3/5B6+ 2/5)O3

In order to synthesize various Perovskite ABO₃ type compounds and their solid solutions, we have applied a novel “melt synthesis technique” rather than conventional solid state reaction techniques. In the melt synthesis, the mixture of oxides or their precursors is melted in a short period of time (1–60 sec) by a strong light radiation in an arc imaging furnace. A spherical molten sample where multiple cations were mixed homogeneously was directly solidified on a copper hearth with a rapid cooling of 10² K/sec. Solid solutions based upon 1:1 ordered Perovskite in the system of Sr(Li_2/5W_3/5)O₃-La(Li_3/5W_2/5)O₃ were synthesized in this technique.     

Sliding mode-based minimum variance and generalized minimum variance controls with O( T 2) and O( T 3) accuracy

The paper deals with the discrete-time sliding mode control with O(T ²) and O(T ³) accuracy, based only on input/output measurements. The linear parts of the control algorithms, recognized as the traditional minimum variance and the generalized minimum variance controls, enable the implementation of the sliding mode control on minimum and non-minimum phase plants. The chattering phenomenon is suppressed by filtering the high-frequency control signal of the sliding mode component through the discrete-time integrator.     

Studies on Electrical Properties and Magnetoelectric Effect of (x)Ni0.8Cu0.2Fe2O4 + (1?x)Ba0.8Pb0.2Ti0.8Zr0.2O3 Composites

Materials consisting of piezomagnetic and piezoelectric phases viz. Ni_0.8Cu_0.2Fe₂O₄ and Ba_0.8Pb_0.2 Ti_0.8Zr_0.2O₃ have been prepared by standard ceramic method. The presence of two phases in the composites has been confirmed by XRD. Variation of the dielectric constant with frequency in the range 100–1 MHz has been studied at room temperature and the variation of dielectric constant with temperature at set frequencies (1 kHz, 10 kHz, 100 kHz and 1 MHz) has been studied. The dielectric relaxation was observed for the compositions with tetragonal structure whereas normal behaviour was observed for cubic structure. All the samples have shown linear magnetoelectric conversion in the presence of a static magnetic field. The dc resistivity (ρ_DC) was studied as a function of temperature in the range 300–773^∘K. The variation of resistivity with temperature shows metal/seconductor behaviour.     

Luminescence of YAl3 (BO3)4: Eu2+, Dy3+ phosphor and its luminescence decay characteristics

Eu²⁺, Dy³⁺ co-doped YAl₃ (BO₃)₄ phosphors are synthesized by sol-gel method. The phosphors show prominent blue luminescence due to the 4f⁷–4f⁶5d transition of Eu²⁺. The emission intensity is greatly improved when Dy³⁺ is doped into the YAl₃ (BO₃)₄:Eu²⁺ system. The 1% Dy³⁺ in Eu²⁺, Dy³⁺ co-doped YAl₃ (BO₃)₄ phosphors is the optimum doping concentration. The luminescence decay characteristics of the samples have also been investigated, exhibiting the decay times of approximately 0.1 μs, which is much shorter compare to other Eu²⁺ doped phosphors.     

Fabrication and characterization of β−FeSi2 thin films prepared by PLD method using Nd:YAG laser

β?FeSi₂ thin films were grown on Si(111) substrates by pulsed laser deposition (PLD) method using a Nd:YAG laser (λ=1064nm, laser energy=50mJ, laser energy density=1.65J/cm², repetition frequency=10Hz). In the fabrication process, three targets of (a) Fe(5N), (b) FeSi₂(3N), and (c) Fe(5N)+FeSi₂(3N) were used. The β?FeSi₂ thin films having the best properties of crystallinity were obtained in the case of (c), in which the first layer as the template was formed with the target of Fe(5N) and then, on top of that, the second layer was deposited with the target of FeSi₂(3N). At this time, it was found that by XRD measurement, the degree of crystallinity of the films of case (c) in which the first layer was introduced as the template improved 1.4 times as much compared with case (a), and that by SEM and AFM observations, surface morphologies also improved. Moreover, it was found that by TEM observation, the β?FeSi₂ thin films grew uniformly along the direction of (220) or (202) from the interface of the Si substrate and the film to the free surface and that by EDS analysis, the compositions of Fe and Si were uniformly distributed. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 39–45, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ eej.20238     

Dielectric Properties and Sintering Characteristics of CaTiO<Subscript>3</Subscript>-(Li<Subscript>1/2</Subscript>Nd<Subscript>1/2</Subscript>)TiO<Subscript>3</Subscript> Ceramics

The dielectric properties and the sintering effect upon microstructure of (1–x) CaTiO₃-x(Li_1/2Nd_1/2)-TiO₃ Ceramics are investigated in this paper. Nd³⁺ and Mg^{2 +} ions co-substitution for Ca^{2 +} on A site improves the sintering characteristic of CaTiO₃ ceramics with forming orthorhombic perovskite structure. The structure of (1 – x) CaTiO₃-x(Li_1/2Nd_1/2)TiO₃ changes from orthorhombic to tetragonal as (Li_1/2Nd_1/2)TiO₃ addition increasing. Limited solubility of (Li_1/2Nd_1/2)TiO₃ in CaTiO₃ forming a part solid solution compound achieves the adjustment of for CaTiO₃ at low sintering temperature. The proper dielectric properties with = 78, tan = 0.0006, = +7 ppm/C are obtained for 0.8Ca_0.67(Nd,Mg)_0.22TiO₃-0.2(Li_1/2Nd_1/2)TiO₃ ceramics.