RESUMO
We report on developing three flashlamp-pumped electro-optically Q-switched Cr:Er:YSGG lasers with the Q-switch based on a La3Ga5SiO14 crystal. The "short" laser cavity was optimized for high peak power applications. In this cavity, 300 mJ output energy in 15â ns pulses at a 3â Hz repetition rate was demonstrated with pump energy below 52 J. However, several applications, such as Fe:ZnSe pumping in a gain-switched regime, require longer (â¼ 100â ns) pump pulse duration. We developed a 2.9 m long laser cavity that delivers 190 mJ of output energy in 85â ns pulses for these applications. We also demonstrated the Cr:Er:YSGG MOPA system producing 350 mJ output energy at 90â ns pulse duration and 47.5 J of pumping, corresponding to an amplification factor of 3.
RESUMO
We report a subharmonic (frequency-divide-by-2) optical parametric oscillator (OPO) with a continuous wavelength span of 3 to 12 µm (-37dB level) that covers most of the molecular rovibrational "signature" region. The key to obtaining such a wide spectral span is the use of an OPO with a minimal dispersion-through the choice of intracavity elements, the use of all gold-coated mirrors, and a special "injector" mirror. The system delivers up to 245 mW of the average power with the conversion efficiency exceeding 20% from a 2.35 µm Kerr-lens mode-locked pump laser.
RESUMO
Mechanically robust and low loss single-mode arsenic sulfide fibers are used to deliver high power mid-infrared sources. Anti-reflection coatings were deposited on the fiber facets, enabling 90% transmission through 20 cm length fibers. 10.3 W was transmitted through an anti-reflection coated fiber at 2053 nm, and uncoated fibers sustained 12 MW/cm2 intensities on the facet without failure. A Cr:ZnSe laser transmitted >1 W at 2520 nm, and a Fe:ZnSe laser transmitted 0.5 W at 4102 nm. These results indicate that by improving the anti-reflection coatings and using a high beam quality mid-infrared source, chalcogenide fibers can reliably deliver ≥10 W in a single mode, potentially out to 6.5 µm.
RESUMO
Using a subharmonic optical parametric oscillator (OPO) based on orientation-patterned GaAs, we produced a broadband instantaneous output that spans 3.6-5.6 µm at 50-dB level (4.4-5.2 µm at 3 dB level), has 110 mW of average power, and is suitable for producing wideband-frequency combs in the mid-infrared. The OPO was synchronously pumped by a compact Kerr-lens mode-locked femtosecond Cr:ZnS oscillator with the central wavelength 2.38 µm and pulse repetition frequency 175 MHz.
RESUMO
Spectroscopic characterization of Fe:ZnSe(Cr:ZnSe) crystals under visible excitation into the charge transfer bands of Transition Metal ions were studied. The excitation efficiencies of mid-IR photoluminescence between (5)T(2)((5)E) and (5)E((5)T(2)) states via direct relaxation to the upper laser levels and via metastable upper (3)T(1) were investigated. It was demonstrated that the latter route is the dominant process for Cr(2+) ions and could provide sufficient pump rate for mid-IR lasing. The pump efficiencies via direct relaxation to the upper laser levels were estimated to be <2% for both ions under 532 nm excitation wavelength.
RESUMO
We propose new transition metal (TM)-doped ZnSe/As2S3:As2Se3 composite materials for mid-IR fiber lasers. The composites are the suspension of crystalline micro- and nanosized TM²âº:ZnSe or TM²âº:ZnS powders in chalcogenide glasses with the refraction index matching. Mid-IR room-temperature lasing of Cr²âº:ZnSe/As2S3:As2Se3 microcomposite material is demonstrated at the 2.4 µm wavelength.
RESUMO
We demonstrate 2.6 µm mid-infrared lasing at room temperature in a planar waveguide structure. Planar waveguides were fabricated using pulsed laser deposition (PLD) by depositing chromium doped zinc selenide thin films on sapphire substrate (Cr2+:ZnSe/sapphire). Highly doped Cr2+:ZnSe/Sapphire thin film sample was also used to demonstrate passive Q-switching of Er:YAG laser operating at 1.645 µm.
Assuntos
Cromo/química , Lasers , Oscilometria/instrumentação , Refratometria/instrumentação , Compostos de Selênio/química , Ressonância de Plasmônio de Superfície/instrumentação , Compostos de Zinco/química , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Raios InfravermelhosRESUMO
We demonstrate, for the first time, 10 W, Er-fiber laser pumped, pure CW, thermally diffusion doped, polycrystalline Cr(2+):ZnS laser operating at 2380 nm. We also show Littrow-grating, "single-knob", wavelength tuning of the laser spanning 1940-2780 nm spectral range with the maximum output power of 7.4 W near the central wavelength of 2400 nm and above 2 W over 1970-2760 nm wavelength range. The laser performs with 40% real optical- and 43% slope efficiency, and shows no output power roll-off up to the highest available incident pump power of 27 W.
Assuntos
Cromo , Lasers , Refratometria/instrumentação , Sulfetos , Compostos de Zinco , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
We demonstrate CW rapidly-tunable (4.5 microm/s), highpower (150 mW), single-longitudinal-mode (120 MHz) single-crystalline Cr(2+):ZnSe laser; CW widely-tunable (2.12-2.77 microm), multi-watt (2 W over 2.3-2.7 microm), polycrystalline Cr(2+):ZnSe laser; CW multi-watt (6 W, at 2.5 microm), highly efficient (48% real efficiency) polycrystalline Cr(2+):ZnSe laser; CW multi-watt (3 W, at 2.5 microm), highly efficient (41% real efficiency) ultra-compact polycrystalline Cr(2+):ZnSe laser; and CW hot-pressed ceramic Cr(2+):ZnSe laser.
Assuntos
Cromo/química , Lasers de Estado Sólido , Compostos de Selênio/química , Compostos de Zinco/química , Desenho de Equipamento , Análise de Falha de EquipamentoRESUMO
We report simple methods of laser active Cr2+:ZnSe powder fabrication with average grain sizes of either approximately 10 or approximately 1 microm without crystal growth stage. Pure, uniformly mixed ZnSe and CrSe powders annealed at 1000 masculineC for 3 days in a sealed evacuated (approximately 10(-4) Torr) quartz ampoule exhibited middle-infrared laser action at room temperature under 1.56 microm excitation of D(2) Raman shifted radiation of Nd:YAG laser. The output-input characteristic clearly demonstrated the threshold-like behavior of the output signal with the threshold energy level of 0.5 and 3 mJ in 2.9 mm spot for 10 and 1 microm grain sizes, respectively.
Assuntos
Cromo/química , Lasers , Compostos de Selênio/química , Compostos de Zinco/química , Simulação por Computador , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Raios Infravermelhos , Modelos Estatísticos , PósRESUMO
The technology of hot-pressed Cr(2+):ZnSe ceramic preparation is reported. Comparative gain-switched lasing of hot-pressed ceramic and CVD grown Cr(2+):ZnSe samples with slope efficiencies up to 10% and output energies up to 2 mJ were demonstrated. This is a milestone in the development of future large scale mid-IR laser systems based on ceramic TM(2+):II-VI materials. This evolving technology has excellent potential as media for practical low cost, high power mid-IR laser applications.
RESUMO
We report a room temperature Fe:ZnSe laser in gain-switched operation and tuning over the 3.9 - 4.8microm spectral range. Mid-IR emission of Fe2+:ZnSe was studied under three regimes of excitation: ordinary optical (2.92mum) excitation of 5T2 excited state of Fe2+; excitation via 5E level of Cr co-dopant (1.56mum); and excitation via photo-ionization transition of Fe2+ (0.532mum). The energy transfer from Cr2+ (5E level) to Fe2+ (5T2 level) under 1.56microm wavelength excitation was observed and resulted in simultaneous RT emission of Fe:Cr:ZnSe crystal over ultra-broadband spectral range of 2- 3 and 3.5-5mum. We also report the observation of mid-IR emission at 3.5- 5mum induced by 2+->3+->2+ ionization transitions of the iron ions in Fe:ZnSe.
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For the first time we demonstrate a multiwavelength, ultrabroadband, continuous-wave, tunable, polycrystalline Cr2+:ZnSe spatially-dispersive laser, operating in the near IR spectral region. We show a dual-wavelength operation of the laser, tunable over a 600 nm spectral range (2200-2800 nm), an ultrabroadband operation of the laser, producing a continuous 135 nm wide spectrum centered at 2500 nm, and show a 200 nm wide (2400-2600 nm) multiline, tunable output spectra, consisting of up to 40 spectral lines. We also show simultaneous tuning of a 20-lines ultrabroadband spectrum over a spectral range of 2200-2800 nm.
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The absorption of hemoglobin (Hb) from controlled urine samples was observed using the technique of evanescent cavity ring-down spectroscopy (e-CRDS). A room temperature, alexandrite laser pumped LiF:F2(+**) color-center pulsed laser was used to excite Hb at 425 nm. A minimum absorbance level of 2.57 x 10(-4) was achieved corresponding to a minimum detectable concentration of Hb in urine of 5.8 nM. These levels could have advantages in the diagnosis of hemoglobinurea. The formation of layers of Hb upon the silica surface allowed for an increased sensitivity for smaller concentrations of Hb than would be expected for only a free floating solution. The formation of the layers also suggested a higher binding constant of Hb to the silica surface than between other layers of Hb molecules. Future studies are underway to understand the effects of salinity on the observed absorption due to the competitive binding of Na+ to the surface. Absorption isotherm modeling will also be used to better understand the development of layers upon the surface.
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A method has been developed for selective detection of the zinc-deficient form of Cu, Zn superoxide dismutase (SOD1) in vitro. Zinc-deficient SOD1 mutants have been implicated in the death of motor neurons leading in amyotrophic lateral sclerosis (ALS or Lou Gerhig's disease). Thus, this method may have applicability for detecting zinc-deficient SOD1 mutants in human ALS patients samples as well as in a transgenic mouse model of ALS and in cultured motor neurons. We determined previously that structural analogs of 1,10 phenanthroline, which react specifically with Cu(I), react with the active Cu(I) of SOD1 when zinc is absent, but not when zinc is also bound, as evidenced by the fact that the reaction is inhibited by pretreatment of the enzyme with zinc. We report herein that bathocuproine, or its water-soluble derivative bathocuproine disulfonate, react with zinc-deficient SOD1 to form a complex which fluoresces at 734 nm when excited at 482 nm. Fluorescent intensity is concentration dependent, thus we propose to use fluorescent confocal microscopy to measure intracellular levels of zinc-deficient SOD1 in situ.
Assuntos
Cobre/metabolismo , Superóxido Dismutase/metabolismo , Zinco/deficiência , Zinco/farmacologia , Substituição de Aminoácidos , Asparagina , Ácido Aspártico , Humanos , Cinética , Doença dos Neurônios Motores/enzimologia , Doença dos Neurônios Motores/genética , Mutagênese Sítio-Dirigida , Proteínas Recombinantes/metabolismo , Espectrometria de Fluorescência/métodos , Espectrofotometria/métodos , Superóxido Dismutase/genéticaRESUMO
Efficient continuous-wave (cw) lasing of Cr(2+):ZnS and Cr(2+):ZnSe crystals in external hemispherical cavities and in a microchip configuration under Er-fiber-laser pumping at room temperature are reported. The key result is what is believed to be the first successful demonstration of cw Cr(2+):ZnS and Cr(2+):ZnSe microchip lasers with maximum output powers of 63 and 100 mW at 2320 and 2520 nm, with slope efficiencies of 53% and 20%, respectively.
RESUMO
Calcium phosphate (CaP) bioceramics, especially hydroxyapatite (HA), have been used as coatings on implants owing to their biocompatible properties. The commercial practice for applying HA coating, plasma spraying, has some disadvantages which limit the long-term stability of the implants. Pulsed laser deposition (PLD) is being investigated as an alternative technique. The purpose of this research was to systematically study the effect of various parameters of the PLD process on the properties of CaP coatings. In this study, three types of HA targets and two laser wavelengths were used to make six categories of coatings. Predominantly crystalline HA coatings were produced under all six categories at optimum conditions, although small amounts of minor phases sometimes were found. Sufficient coating/substrate bond strength was also obtained. A wide variety of coating morphologies was obtained, from rather dense and uniform to rough and porous. The important factors that affected the morphology included target properties, vacuum level, deposition temperature, and laser wavelength and energy density. PLD's ability to produce both amorphous and crystalline, and both smooth/dense and rough/porous coatings may be a unique advantage.
Assuntos
Fosfatos de Cálcio , Cerâmica , Materiais Revestidos Biocompatíveis , Materiais Biocompatíveis , LasersRESUMO
Polarized Raman spectra have been obtained for tetragonal lysozyme single crystals of different relative quality. The Raman band at 507 cm-1, which corresponds to the totally symmetric stretch vibration of the gauche-gauche-gauche (ggg) disulfide bridges of the protein, has been shown to possess different polarization characteristics compared with the gauche-gauche-trans (ggt) disulfide bridge band at 528 cm-1. The relative intensities of the ggg and ggt bands in the polarized Raman spectra have been numerically estimated for a number of tetragonal lysozyme single crystals, the X-ray diffraction data of which are available from the Protein Data Bank. On the basis of comparison between the experimental and calculated polarization characteristics of the disulfide Raman lines, the following main conclusions have been drawn. The orientation of the protein molecules correlates with the average orientation of their ggg disulfide bridges. This in turn can be described by the rhoggg value which reflects the average orientation of the S-S bonds with respect to the Z crystallographic axis and can be determined from polarized Raman spectra. Crystals of better quality are characterized by a better alignment of the protein molecules with respect to the Z axis, a smaller perturbation of the protein molecules in the crystal lattice and a somewhat higher interlattice water content.
Assuntos
Muramidase/química , Análise Espectral Raman , Animais , Galinhas , Cristalização , Cistina/química , Dessecação , Vibração , ÁguaRESUMO
We report experimental and theoretical studies of the temporal, spectral, and spatial features of a superbroadband laser. The results obtained show that the superbroadband room-temperature operable LiF:F(2)(-) color-center laser can provide low-coherence, high-intensity laser radiation with a spectral width of 1400 A centered at 1.14 mum and 700 A in the visible range from green to red and exhibit good spatial collimation with a divergence of between 5 and 6 mrad. Oscillation of all the lines of a superbroadband spectrum is completely synchronous and occurs almost simultaneously with the pump pulse, exhibiting 4-9-ns pulse delay at 20-ns pump pulse duration. Second-harmonic generation of superbroadband oscillation spectrum was realized with an overall efficiency of 10%.