Room-temperature 3.4- mum Dy:BaYb(2)F(8) laser

We have demonstrated a room-temperature laser on the (6)H(13/2) - (6)H(15/2) transition of Dy(3+) in Dy:BaYb(2)F(8) at 3.40 mum . A pulsed 1.3-microm Nd:YAG laser was used as the pump. Our measured spontaneous-emission spectrum for the (6)H(13/2) - (6)H(15/2) band indicates that this laser should be continuously tunable between 3.0 and 3.4 mum .     

Demonstration of room-temperature laser action at 2.5 mum from Cr(2+):Cd(0.85)Mn(0.15)Te

Room-temperature laser action from Cr(2+)-doped Cd(0.85)Mn(0.15)Te has been demonstrated for what is believed to be the first time. We achieved pulsed laser operation centered at ~2.5mu m by pumping into the mid-infrared absorption band of Cr(2+) ions by use of the 1.907- mum output of a H(2) Raman-shifted Nd:YAG laser. The output of the free-running Cr(2+):Cd(0.85)Mn(0.15)Te laser had a width of ~50 nm (FWHM), and the slope efficiency was calculated to be 5.5% under nonoptimum conditions.     

Room-temperature diode-pumped Yb:KYF(4) laser

Continuous-wave laser action has been demonstrated in a diode-pumped Yb:KYF(4) crystal. Crystal growth, spectroscopic measurements, and laser results are presented. A maximum output power of 505 mW, a slope efficiency of 43%, and a continuous wavelength tunability range of 65nm, from 1013 to 1078 nm, have been obtained at room temperature.     

Highly efficient CW laser operation in 4 at. % Tm~(3+) and 4 at. % Y~(3+) codoped CaF_2 crystals

Tm:CaF_2 and Tm;Y:CaF_2 single crystals were prepared by the temperature gradient technique. The spectral properties of Tm;Y:CaF_2 single crystals were investigated and compared with those of Tm:CaF_2. It was demonstrated that codoping with Y~(3+) ions could efficiently improve the spectroscopic properties. Tm;Y:CaF_2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections, and much longer fluorescence lifetimes of the upper laser level(Tm~(3+):~3H_4 level) than Tm:CaF_2 crystals. Continuous-wave(CW) lasers around 1.97 μm were demonstrated in 4.0 at. % Tm,4.0 at. % Y:CaF_2 single crystals under 792 nm laser diode(LD) pumping. The best laser performance has been demonstrated with a low threshold of 0.368 W, a high slope efficiency of 54.8%, and a maximum output power of 1.013 W.     

Er~(3+),Yb~(3+):glass-Co~(2+):MgAl_2O_4 diffusion bonded passively Q-switched laser

A Co~(2+):spinel passively Q-switched erbium-ytterbium-phosphate glass bonded laser pumped at 940 nm is reported.A pulse energy of 210 μJ, a peak power over 70 kW, and beam quality M~2 parameter of 1.2 are obtained under a pump power of 235 mW. An unbonded laser output experiment with the same dimension of the active material and the saturable absorber as the bonded laser output experiment is carried out. The reason why the output in the bonded laser is improved is determined.     

Green Er(3+):YLiF(4) upconversion laser at 551nm with Yb(3+) codoping: a novel pumping scheme

We report room-temperature continuous-wave upconversion laser emission on the green transition (4)S(3/2)?(4)I(15/2) in Er(1%), Yb(3%):YLiF(4) at 551nm. Green laser operation was obtained for titanium-sapphire pump wavelengths continuously tunable between 955 and 974.5nm. Codoping with Yb(3+) resulted in a more efficient excitation of the upper laser level by upconversion processes. The maximum green laser output power was 37mW at an incident titanium-sapphire pump power level of 1580mW at 966nm.     

High-power diode-pumped picosecond Nd(3+):YVO(4) laser

A diode-pumped Nd(3+):YVO(4) laser passively mode locked by a nonlinear mirror based on second-harmonic generation has been developed. Pumping with a fiber-coupled 10-W diode array, we generated nearly diffraction limited, linearly polarized 11-ps pulses at 1064nm, with average power of 2.7 W at a 150-MHz repetition rate. Pulses as short as 7.9 ps were measured with reduced output power (1.35 W) by optimal focusing in the nonlinear crystal.     

Radical-recombination luminescence,ion-luminescence and photoluminescence of CaGa2S4:Eu

CaGa₂S₄ based luminophors have recently attracted significant attention due to their high efficiency. Very little is known now about the surface and near surface luminescence of these luminophors. The ion-luminescence of CaGa₂S₄:Eu excited by low energy hydrogen ions (up to 3 keV) and the radical-recombination luminescence excited by neutral hydrogen atoms of thermal energies have been studied. The latter is due to chemical energy released at the surface during heterogeneous recombination of atoms into molecules (∼4 eV per recombination event). The radical-recombination luminescence is likely the most surface kind of luminescence, while the ion-luminescence is the luminescence of near-surface layers. In this regard the photoluminescence is the bulk one of with which the characteristics of the surface luminescence might be compared.     

Direct diode-pumped continuous-wave near-inf rared tunable laser operation of Cr(4+):forsterite and Cr(4+):Ca(2)GeO(4)

Continuous-wave tunable laser operation of direct diode-pumped Cr(4+):Mg(2)SiO(4) (Cr:forsterite) and Cr(4+):Ca(2)GeO(4) (cunyite) crystal were demonstrated. Diode-pumped Cr:forsterite was tunable over the 1236-1300-nm spectral range. The maximum output of 10 mW was measured at 1260 nm for 640 mW of pump power absorbed by the crystal. Diode-pumped laser operation of cunyite was also demonstrated over the 1390-1475-nm range. Free-running 20-mW output was centered at 1410 nm.     

NaZnLa(PO_4)_2中Ce~(3+)和Tb~(3+)的发光

采用高温固相反应合成了NaZnLa(PO4 ) 2 中掺杂Ce3 +、Tb3+的荧光体 ,对其晶体结构、发光行为进行了研究 ,并尝试对NaZnLa(PO4 ) 2 ∶Ce ,Tb荧光体进行调制。NaZnLa(PO4 ) 2 是LaPO4 的同构物 ,为单斜晶系独居石结构 ,从XRD谱数据得到NaZnLa(PO4 ) 2 基质的晶胞参数为a =0 6 82 3nm ,b =0 70 45nm ,c =0 6 497nm ,β =10 3 9° ,V =0 30 3nm3,其晶胞参数与单斜LaPO4 的晶胞参数相似。在NaZnLa(PO4 ) 2 ∶Ce ,Tb荧光体中 ,Ce3 +对Tb3+有良好的敏化作用 ,掺杂适量的BO3 -3 、Al3 +、Dy3 +,可以增强发光亮度     

Fourfold output power enhancement and threshold reduction through thermal effects in an Er(3+)/Yb(3+)-codoped optical fiber laser excited at 1.064 mum

Thermally induced output power enhancement and threshold reduction in an Er(3+)/Yb(3+) -codoped optical fiber laser at 1.54mum pumped by 1.064-mu;m cw radiation is demonstrated. Steady fourfold output power increase and threshold decrease were achieved by heating of the Yb(3+) -sensitized Er(3+) -doped fiber laser medium in the temperature range 23-150 degrees C degrees . The laser efficiency thermal behavior is assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process.     

Dual-wavelength continuous-wave cascade oscillation at 3 and 2 mum with a holmium-doped fluoride-glass fiber laser

We have demonstrated dual-wavelength continuous-wave oscillation at 3 and 2 mum with a Ho-doped ZrF(4)- BaF(2)- LaF(3)- AlF(3)- NaF fluoride-glass fiber laser by use of a cascade oscillation scheme. We have shown that the fiber laser operates with a high slope efficiency of 52% (at 3 and 2microm) with respect to the absorbed pump power. With a 6.5-m-long fiber we achieved an output power of 90 mW at each of the wavelengths that was limited only by the pump power, and the 3-microm output power is to our knowledge higher than any previously reported level with 3-mum Ho(3+) -doped fiber lasers.     

Polarized transmission intensity studies at and below energy gap of wide-gap single crystalline CaGa2S4

Polarized transmission intensity studies have been performed on wide-gap single crystalline CaGa₂S₄ at room temperature. The effective value of the partial birefringence in (100) plane is determined to be comparatively large varying from 0.14 to 0.50 with increasing photon energy from 1.9 to 3.5 eV. Four structures, which were preliminary ascribed to the critical points of interband optical transitions are displayed by ellipsometric examination with the aid of a spectroscopic phase-modulated ellipsometer in the spectral range 1.5–6.3 eV. These points, together with band gap singularity, are believed to largely contribute into the optical properties below the energy gap of biaxial CaGa₂S₄. The pseudo values of two major components of dielectric function tensor of CaGa₂S₄ are given for the first time.     

Diode-pumped Pr(3+):KY(3)F(10) red laser

We report the first observation to our knowledge of room-temperature continuous-wave laser operation of a Pr(3+):KY(3)F(10) single crystal at 644.5 nm, pumped by a blue GaN laser diode emitting at 446 nm. With a 2.5% transmission output coupler and a nonoptimized optical cavity, an output power of 39 mW was obtained at 644.5 nm with a laser threshold of 125 mW and a differential slope efficiency of 23%.     

Performance of a low-loss pulsed-laser-deposited Nd:Gd(3) Ga(5)O(12) waveguide laser at 1.06 and 0.94 mum

We report the laser performance of a low-propagation-loss neodymium-doped Gd(3)Ga(5)O(12) (Nd:GGG) waveguide fabricated by pulsed-laser deposition. An 8- mum -thick crystalline Nd:GGG film grown upon an undoped Y(3)Al(5)O(12) substrate lases at 1.060 and 1.062 microm when pumped by a Ti:sapphire laser operating at 740 or 808nm.Using a 2.2% output coupler, we observed a 1060-nm laser threshold of 4mW and a slope efficiency of 20%. Laser action was also achieved, for what we believe is the first time in Nd:GGG, on the quasi-three-level 937-nm transition. With a 2% output coupler at this wavelength a laser threshold of 17mW and a 20% slope efficiency were obtained. This demonstration of low propagation loss combined with the fact that these waveguides have a very high numerical aperture (0.75) makes pulsed-laser-deposited thin films attractive for high-power diode-pumped devices.     

掺杂Gd^3＋对Y2O2S：Eu^3＋发光特性的影响

在红色荧光粉Ｙ２Ｏ２Ｓ：Ｅｕ＾３＋的制备过程中掺入了不同浓度的Ｇａ２Ｏ３;发现在掺入适当浓度的Ｇａ２Ｏ３的情况下,可以增强发射强度并改善其电压特性,即在保证所要求的发光颜色、粒径和其它物理及化学特性的条件下,可改善发射强度与激发电压间的关系,讨论和分析了强度被增强的起因。Ｇａ＾３＋对Ｙ＾３＋的置换,减少了因Ｅｕ＾３＋对Ｙ＾３＋转换所引起的晶格的畸变,从而减弱了无辐射过程及因晶格畸变所造成的能量损失     

Erbium:YAG (2.94 mum) laser effects on dental tissues

Past trials with soft and calcified tissues have demonstrated that long pulse train (2.5 mus) Er:YAG (2.94 mum) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue removal without significant surrounding damage. Ground sections and SEM sections of teeth showed little or no melting or ash formation in adjacent dentin and enamel and no visible change in the pulp chamber. The surfaces produced by laser ablation were rough and irregular with craters and grooves. Average temperature change in the pulp chamber monitored during tooth preparation was 2.2 degrees Centigrade. These findings suggest that constantly available water aids vaporization and microexplosions, increasing the efficiency of tooth structure removal, and aids in cooling of the tooth structures. The long pulse Er:YAG (2.94 mum) laser may be an effective method for tooth reduction applications when used with a water mist.     

Passively Q-switched 1.34- mum Nd:YVO(4) microchip laser with semiconductor saturable-absorber mirrors

We demonstrate a passively Q -switched diode-pumped 1.34- microm Nd:YVO(4) microchip laser. We achieved single-frequency, 230-ps pulses by using an InGaAsP semiconductor saturable-absorber mirror. We can vary the pulse width and the repetition rate from 230ps to 12ns and from 30 kHz to 4 MHz, respectively, by changing the design parameters of the saturable absorber, the thickness of the crystal, and the pump power.     

Sonochemical synthesis of Dy2(CO3)3 nanoparticles,Dy(OH)3 nanotubes and their conversion to Dy2O3 nanoparticles

Dysprosium carbonates nanoparticles were synthesized by the reaction of dysprosium acetate and NaHCO₃ by a sonochemical method. Dysprosium oxide nanoparticles with average size about 17 nm were prepared from calcination of Dy₂(CO₃)₃·1.7H₂O nanoparticles. Dy(OH)₃ nanotubes were synthesized by sonication of Dy(OAC)₃·6H₂O and N₂H₄. The as-synthesized nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Photoluminescence measurement shows that the nanoparticles have two emission peaks around 17,540 cm^?1 and 20,700 cm^?1, which should come from the electron transition from ⁴F_9/2 → ⁶H_15/2 levels and ⁴F_9/2 → ⁶H_13/2 levels, respectively. The effect of calcination temperature and sonication time was investigated on the morphology and particle size of the products. The sizes could be controlled by the feeding rate of the precipitating agent (NaHCO₃ and N₂H₄) and slower feeding rate lead to smaller nanoparticles.