Laser Performance Parameters Research Articles

Growth and spectroscopic properties of Yb 3+-doped BaLaLiWO 6 crystal

This paper reports the growth and spectral properties of Yb 3+:BaLaLiWO 6 crystals. A Yb 3+:BaLaLiWO 6 crystal with dimensions of Ø20 × 15 mm 3 has been successfully grown by the Czochralski method. The spectral properties of Yb 3+:BaLaLiWO 6 crystals have been investigated. The laser performance parameters β min, I sat and I min of Yb 3+:BaLaLiWO 6 crystals have been also established. The above results suggest Yb 3+:BaLaLiWO 6 crystal as a potential laser crystal material.

Growth and spectral properties of Yb 3+-doped Li 3Ba 2Y 3(MoO 4) 8 crystal

This paper reports the growth and spectral properties of Yb 3+:Li 3Ba 2Y 3(MoO 4) 8 crystals. An Yb 3+:Li 3Ba 2Y 3(MoO 4) 8 crystal with dimensions of 25 mm × 11 mm × 15 mm has been successfully grown by the TSSG method. The spectral parameters of Yb 3+:Li 3Ba 2Y 3(MoO 4) 8 crystal have been estimated. The laser performance parameters β min, I sat, and I min of the crystal have been also established. The results regard the Yb 3+:Li 3Ba 2Y 3(MoO 4) 8 crystal as a potential solid-state laser crystal material.

Influences of Yb 3+ ion concentration on the spectroscopic properties of silica glass

We investigated optical spectroscopic properties of silica glass doped with ytterbium (Yb 3+) ions to assess their lasing performance in diode-laser pumped systems. The Yb-doped silica glass preforms were fabricated by solution doping technique using the MCVD process. The stimulated emission cross-section and laser performance parameters were determined from the measured absorption spectra using the method of reciprocity. Fluorescence decay characteristics were observed to be deviated from exponential behavior as the Yb 3+ ions doping level increases and there exists a lifetime quenching behavior related to the cluster effect of Yb 3+ ions into silica glass. Nevertheless, lasing parameters indicated that clustering of Yb 3+ ions does not significantly affect the spectral properties relevant to the predicted lasing performance when concentration is low, but becomes predominant at higher concentration.

Microstructure and wear property of carbon nanotube carburizing carbon steel by laser surface remelting

Carbon nanotube was used to carburize the surface of medium carbon steel and mild steel, respectively, by means of laser surface remelting. The slurry of carbon nanotube of ethanol was coated on the surface of the materials prior to laser irradiation. Microstructures, microhardness and wear property of the surface layers treated by different laser performance parameters were studied. Graphite coating was also used for carburizing. The results showed that both carbon nanotube and graphite were dissolved in the surface molten layer, leading a carburized hardening layer on the surface of the substrate. However, different microstructures formed in the carburizing layers, depending mainly on the type of carburization materials, carbon nanotube or graphite. The carbon nanotube hardening layer exhibits a little higher hardness than the graphite hardening layer. The carburized layer greatly increases the wear resistance of the base material.

Evaluation of Optical Properties of Self-Frequency-DoublingCrystal Yb:GdYAl3(BO3)4 for Laser Applications

Yb:GdYAl3(BO3)4(Yb:GdYAB) is investigated as a newlaser crystal for potential applications in self-frequency doubling.The emission and absorption properties of Yb:GdYAB crystal are studied,and the emission decay times of the upper laser level are measured. Theemission cross sections are evaluated using the absorption crosssection and principle of reciprocity. The other laser performanceparameters, such as the minimum inversion fraction βmin,pump saturation intensity Isat and minimum pumpintensity Imin, are also calculated. Theresults are discussed in the framework of requirements for an effectivediode-pumped Yb3+ laser system. Yb:GdYAB is expected to exhibitthe most useful laser properties and to be superior to Yb:YAB crystalthat has been excellent self-frequency-doubling crystal at present inmany key spectroscopic parameter values.

Growth and spectral characteristics of Yb 3+-doped LiLa(MoO 4) 2 crystal

A Yb 3+-doped LiLa(MoO 4) 2 crystal with dimension of ∅20×35 mm 3 has been grown by the Czochralski method. The polarized optical absorption and emission spectra of the crystal have been investigated. The Yb 3+:LiLa(MoO 4) 2 crystal has a broad absorption FWHM of 29 nm at 977 nm. The absorption cross-sections of the crystals are 1.93×10 −20 cm 2 and 1.56×10 −20 cm 2 at 977 nm for π- and σ-polarization, respectively. The emission cross-sections of the crystals are 1.53×10 −20 and 1.00×10 −20 cm 2 at 1011 nm for π- and σ-polarization, respectively. The radiative lifetime and fluorescence lifetime of the Yb 3+:LiLa(MoO 4) 2 crystal are 391 and 636 μs, respectively. The laser performance parameters β min, I past, and I min of the crystal have been calculated. The investigated results shown the Yb 3+:LiLa(MoO 4) 2 crystal is expected as a potential solid-state laser crystal materials.

Growth and spectral properties of Yb3+ doped LaVO4 crystal

The spectroscopic characterizations of Yb3+:LaVO4 crystal at room temperature have been investigated using the reciprocity method (RM) and the Füchtbauer-Ladenburg (F-L) method. The absorption and emission cross-sections are 2·11 × 10−20 cm2 at 978 nm and 8·5 × 10−20 cm2 at 1041 nm respectively. The fluorescence lifetime is 400 μs. The laser performance parameters βmin, Ipsat and Imin were obtained. Based on the spectroscopic characterization of Yb3+:LaVO4 crystal, it was suggested as a candidate of laser gain materials.

Thermal Stability and Spectroscopic Properties ofYb3+-Doped New Gallium–Lead–Germanate Glass

Yb3+-doped new gallium–lead–germanate glass is presented.Thermal stability, spectroscopic and laser performance parameters ofthe Yb3+-doped new gallium–lead–germanate glass are calculated.The results show that the Yb3+-doped new gallium–lead–germanateglass has good thermal stability (ΔT = 198°C), high stimulatedemission cross section (0.79 pm2), and long fluorescencelifetime (1.46 ms). Compared with other Yb3+-doped glass hosts,the Yb3+-doped new gallium–lead–germanate glass has better laserperformance parameters and laser properties, indicating thatYb3+-doped new gallium–lead–germanate glass is a promising lasermaterial for short pulse generation in diode pumped lasers, short pulsegeneration tunable laser, high-peak power and high-average power lasers.

Extension of wavelength-modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases

Tunable diode laser absorption measurements at high pressures by use of wavelength-modulation spectroscopy (WMS) require large modulation depths for optimum detection of molecular absorption spectra blended by collisional broadening or dense spacing of the rovibrational transitions. Diode lasers have a large and nonlinear intensity modulation when the wavelength is modulated over a large range by injection-current tuning. In addition to this intensity modulation, other laser performance parameters are measured, including the phase shift between the frequency modulation and the intensity modulation. Following published theory, these parameters are incorporated into an improved model of the WMS signal. The influence of these nonideal laser effects is investigated by means of wavelength-scanned WMS measurements as a function of bath gas pressure on rovibrational transitions of water vapor near 1388 nm. Lock-in detection of the magnitude of the 2f signal is performed to remove the dependence on detection phase. We find good agreement between measurements and the improved model developed for the 2f component of the WMS signal. The effects of the nonideal performance parameters of commercial diode lasers are especially important away from the line center of discrete spectra, and these contributions become more pronounced for 2f signals with the large modulation depths needed for WMS at elevated pressures.

Phase diagram, growth and spectral characteristic of Yb 3+:KY(WO 4) 2 crystal

The phase diagram of Yb 3+: KY(WO 4) 2–K 2WO 4/KF has been determined by means of XRD and DSC. Yb 3+:KY(WO 4) 2–K 2WO 4/KF system has very low volatility, and has high solubility and a large growing temperature region of about 200 K for Yb 3+: KY(WO 4) 2 crystal. Yb 3+: KY(WO 4) 2 crystal with the dimension up to 37×22×10 mm 3 has been grown from a flux of 40 mol%K 2WO 4/KF by TSSG method. The hardness of Yb 3+:KY(WO 4) 2 is 286.3 VDH. Yb 3+: KY(WO 4) 2 crystal has large absorption and emission cross-sections which are 1.67×10 −20 cm 2 at 981 nm and 1.82×10 −20cm 2 at 1024 nm respectively for E// X. The fluorescence lifetime is 1.23 ms at room temperature. The laser performance parameters of Yb 3+: KY(WO 4) 2 crystal were evaluated.

Photo-physical and lasing characterisation of neat films of a thianthrene-substituted distyrylbenzene dye (Thianthrene-DSB)

Wave-guided travelling-wave laser action and distributed-feedback laser action of a thianthrene substituted distyrylbenzene (Thianthrene-DSB) in neat thin films on glass-substrates and corrugated gratings have been achieved by optical excitation with picosecond laser pulses. The Thianthrene-DSB dye is a model compound of previously studied Thianthrene-PPV polymers. It was found that the low molar-mass model and the corresponding polymers are similar in solid-state lasing behaviour. Some laser performance parameters are determined like laser threshold, and spectral narrowing. The Thianthrene-DSB travelling-wave laser emits at 544 nm and the threshold pump pulse energy density is about 9 μJ cm −2. The distributed feedback laser is wavelength tunable in the range from 520 to 580 nm by variation of the groove spacing and the film thickness. The refractive index and absorption cross-section spectra of the films are determined. The fluorescence behaviour of the films (fluorescence quantum distribution, fluorescence quantum yield, degree of fluorescence polarisation, fluorescence lifetime) is analysed. A fluorescence quantum yield of about 0.6 is found for both Thianthrene-DSB neat films and Thianthrene-DSB dissolved in dioxane.

Emission properties of ytterbium-doped GeO 2–TeO 2 glasses

In this Letter we present a promising trivalent-ytterbium-doped GeO 2–TeO 2–Nb 2O 5–BaO laser glass with better laser performance parameters and emission properties. It is shown that with increasing glass modifier (BaO) content, spectroscopic properties of activator in this glass such as absorption cross section, integrated absorption area and emission cross section decrease, and with increasing GeO 2/TeO 2 ratio the highest value of emission properties appear near 30 mol% GeO 2. Compared to all the ytterbium-doped laser glasses reported in published papers, the present glass has much higher gain parameter and lower minimum pump intensity. The better emission and laser properties may make this glass become promising candidate gain medium for high power solid state lasers.

Spectroscopic properties of Yb 3+ in bismuth borate glasses

Absorption spectra, fluorescence spectra and fluorescence decay curves have been measured at room temperature. Spectroscopic and laser performance parameters of Yb 3+ in bismuth borate glasses with different compositions and Yb 3+ concentrations were calculated. The effects of the host glasses compositions and Yb 3+ concentration on the spectroscopic and laser performance parameters have been analyzed. The effect of radiation trapping on the spectroscopic properties has also been discussed. The results show that the Yb 3+-doped bismuth borate glass is a promising laser material.

Evaluation of spectroscopic properties of Yb 3+ in tetraphosphate glass

The tetraphosphate glasses with various Yb 3+ concentrations were prepared. The absorption and fluorescence emission spectra were measured. The spectroscopic properties and laser performance parameters of Yb 3+ in tetraphosphate glasses were calculated. The result shows that Yb 3+-doped tetraphosphate glass exhibits excellent spectroscopic properties. The disagreement between the reciprocity method (RE) and Fuchtbauer–Ladenburg formula in calculations of Yb 3+ spectroscopic properties was discussed using the radiation trapping effect. The effects of OH − contents on emission properties of Yb 3+ were investigated.

SPECTROSCOPIC PROPERTIES OF Yb3+-DOPED TETRAPHOSPHATE GLASS

The tetraphosphate glasses with various Yb3+ dopant were prepared. The absorption and fluorescence emission spectra were measured. The spectroscopic properties and laser performance parameters of Yb3+ in tetraphosphate glasses were calculated. The disagreement between the reciprocity method and Fuchtbauer-Ladenburg formula was discussed using the radiation trapping effect. The effects of Yb3+ and OH- contents on emission properties were investigated. The result shows that Yb3+-doped tetraphosphate glass exhibits excellent spectroscopic properties.

Optimization of spectroscopic properties of ytterbium-doped laser glasses

Four laser glasses with high emission cross sections are experimentally obtained. The laser performance parameters are determined from the spectroscopic parameters of these glasses and compared with those of developing laser glasses abroad. It is shown that Yb3+-doped telluorogermanate, Yb3+-doped niobosilicate glasses have the highest emission cross section and gain coefficient, the smallest minimum pumping intensity and saturation pumping intensity, and the lowest minimum fraction of excited ions. Yb3+-doped borate glass follows just behind them. These glasses have some spectroscopic advantages over laser glasses developed recently elsewhere. Yb3+-doped phosphate glass is comparable to phosphate laser glass which had high emission cross section and was developed recently by HOYA Corporation in Japan. The domestic glasses with optimum spectroscopic properties may be promising candidates for applications in high-average power and high-peak power solid state lasers, especially laser for the next generation laser nuclear fusion facility.

Experimental and theoretical investigation of a coaxial pumped photolytic atomic bromine laser

This paper describes the results from a combined experimental theoretical investigation of a coaxial pumped photolytic bromine laser. A 532-nm pump was used to photodissociate IBr and produce Br*(/sup 2/P/sub 1/2/) with subsequent lasing on the (/sup 2/P/sub 1/2/)/spl rarr/(/sup 2/P/sub 3/2/) transition. Experimental results are presented for output energy, mode buildup time and small-signal gain as a function of pump energy and mirror outcoupling fraction. A simplified rate equation model was developed to predict the laser performance parameters and shows good agreement with the laser output energy and small-signal gain.

Wear and failure of titanium nitride coated high speed steels and cemented carbides: H. Hnninen et al. (Helsinki University of Technology, Helsinki, Finland.) Metallurgical Trans. A, vol 27a, no 9, 1996, 2796–2808

Carbon nanotube was used to carburize the surface of medium carbon steel and mild steel, respectively, by means of laser surface remelting. The slurry of carbon nanotube of ethanol was coated on the surface of the materials prior to laser irradiation. Microstructures, microhardness and wear property of the surface layers treated by different laser performance parameters were studied. Graphite coating was also used for carburizing. The results showed that both carbon nanotube and graphite were dissolved in the surface molten layer, leading a carburized hardening layer on the surface of the substrate. However, different microstructures formed in the carburizing layers, depending mainly on the type of carburization materials, carbon nanotube or graphite. The carbon nanotube hardening layer exhibits a little higher hardness than the graphite hardening layer. The carburized layer greatly increases the wear resistance of the base material.

Simultaneous emission of the HF and N/sub 2/ lines from a plasma cathode TEA laser

Simultaneous laser action from HF and N/sub 2/ is obtained, from a plasma cathode TEA laser, for the first time. The sliding discharge along the surface of a dielectric is used as a plasma cathode, for the main volumetric discharge. The laser operates at atmospheric pressure, with a gas mixture of SF/sub 6/:C/sub 3/H/sub 8/:N/sub 2/:He. For a typical flow rate ratio of 0.27:0.024:0.2:19.8 1 min/sup -1/, it produces simultaneously 160 mJ HF and 0.6 mJ N/sub 2/ laser outputs at 0.43% and 1.4/spl times/10/sup -3/% efficiencies respectively, at the moderate charging voltage of 28.5 kV. These output characteristics are obtained from a small active discharge volume and length of 10/sup 6/ cm/sup 3/ and 38 cm respectively. These values extend the performance, recently reported in the literature, of a sliding discharge HF/N/sub 2/ laser with corresponding simultaneous energy outputs of 12 mJ HF and 1.1 mJ N/sub 2/, to a higher energy output level, thus making the device suitable for a broader range of applications. This novel dual wavelength HF/N/sub 2/ laser system presented, can be particularly convenient for medical experiments, where the IR beam can be used for tissue ablation, while the UV beam can be used as the excitation source for fluorescence spectroscopic measurements, for the evaluation of the ablation process. Details are presented on the dependence of the laser performance parameters, such as output energy, discharge voltage and current and structure of the laser output pulses on the mixture composition and the circuit parameters.

Chemical laser systems analysis

This paper presents a means by which the chemical laser device weight can be minimized with respect to its performance and the device power minimized with respect to the target range. Chemical laser performance parameters such as the specific power and nozzle power flux are then used in conjunction with weight and propagation models to determine system effectiveness. A measure of merit is given by which systems can be contrasted. An illustrative example is included in which DF and Iodine laser systems are compared for an airborne scenario. 14 references.