激光微织构硬质合金表面润湿性

为了研究硬质合金表面激光微织构对其表面润湿性的影响,利用光纤激光不同功率（3,5,7,9,10 W）及不同加工次数（1,2,3,4,5）加工微凹坑,采用VHX1000c超景深三维显微镜、光学显微镜分析微凹坑形貌,利用CAM 200光学接触角仪测量表面微织构（微凹坑直径、深度和织构密度）与润湿性之间的关系。结果表明：随着激光功率的增大,微凹坑深度增加,直径变化不明显;硬质合金表面的亲水性能随着微凹坑深度的增加而减小;随着微凹坑直径的增大,亲水性增强;随着微织构密度的增加,亲水性出现极值。     

Carbon Dioxide Measurement Based on Multimode Diode Laser Correlation Spectroscopy Employing Wavelength Modulation Techniques

The use of a tunable multimode diode laser system based on correlation spectroscopy and wavelength modulation spectroscopy to measure the concentration of the carbon dioxide in ambient air through the 2 υ₁ + 2υ₂ + υ₃ absorption lines around 1570 nm is reported. The carbon dioxide concentrations are derived from the relationship between the normalized second-harmonic signal peak heights of the measurement and reference signals. The validation of the system is conducted by a set of experiments with controlled carbon dioxide and nitrogen mixtures. The correlation and standard deviation between the measured and actual carbon dioxide concentrations are 0.9973 and 4.03%, respectively, over the tested range. A detection limit of 340 ppm m was achieved using 30 successive measurements during 30 min. All these results demonstrated potential utility of the system for carbon dioxide sensing.     

Novel shooting method with simple control strategy for fiber lasers

A novel shooting method with excellent simple control strategy is developed for solving the failure to convergence of the traditional shooting methods themselves in fiber lasers model. Compared with the published literature, the novel shooting method provides a clear physical understanding method for getting the threshold pump power and the exact results with given random functions in Yb³⁺-doped fiber lasers and Er³⁺-doped fiber lasers. Then, the results in Er³⁺-doped fiber lasers and Yb³⁺-doped fiber lasers demonstrate that the solutions using the novel shooting method has high accuracy of 10⁻⁸ W with several iteration steps, which have extended the applicable range of the end-pumped power even lower than 1 mW pump power. Furthermore, compared with 1480 nm pump for the threshold and slope efficiencies of the Er³⁺-doped fiber lasers, 978 nm fiber lasers can extend wider scope of application and be pump source in the coming future. Finally, the lower threshold and higher slope efficiency at 975 nm than those of 910 nm pump in Yb³⁺-doped fiber lasers, 975 nm pump laser provides for broad band excellent cladding pump source.     

光纤非相干合成光束在湍流大气中的传输实验研究

进行了六路100 W量级光纤非相干合成光束在实际大气湍流中的传输实验,将六路光斑直径为9 mm的单模光纤光束分别扩束,扩束后的光斑直径为90 mm。基于倾斜镜的合束系统来控制各路光束的指向,在不同强度的湍流条件中,通过主镜口径为440 mm的发射系统水平聚焦传输至470 m处。倾斜控制系统闭环工作时,一倍衍射极限内的桶中功率占目标处总功率的比值是开环工作时的1.7倍左右,随着大气湍流的强度变弱,此比值变大。     

声光调Q纳秒脉冲全光纤超连续谱光源

基于声光调Q技术的纳秒脉冲光纤激光超连续谱光源系统为全光纤结构,使用普通的传能光纤作为超连续谱的产生介质,通过改变泵浦功率和调制频率,可获得不同的超连续谱输出。实验结果表明：泵浦功率越大,调制频率越低,传能光纤越长,光谱展宽越宽。当传能光纤为200 m、调制频率为1 kHz、占空比为1.0%、泵浦功率为4.68 W时,获得谱线宽度超过700 nm的超连续谱输出。该系统可作为超连续谱光源的一种参考方案。     

Nd:YVO4自受激拉曼激光器调Q锁模特性

利用Nd:YVO4激光晶体的自受激拉曼效应,结合Cr:YAG被动锁模技术和倍频技术,实现了结构紧凑的1176 nm和588 nm黄光锁模激光输出。激光器为LD端面泵浦,三镜折叠腔结构,并且采用了透过率为10%的输出镜。Nd:YVO4晶体长度为10 mm,Nd3+离子掺杂质量分数为0.2%,Cr:YAG晶体的初始透过率为67%。10 W激光泵浦时,1176 nm激光平均输出功率为123 mW,调Q包络宽度为6 ns,调Q包络内的锁模脉冲重复频率高达1 GHz。588.2 nm 黄光的平均输出功率为8 mW。     

宽波段连续调谐全固态CW PPMgLN光学参量振荡器

利用半导体激光泵浦输出1064 nm波长的全固态连续Nd:YVO4激光器作为泵浦源,采用周期调谐和温度调谐组合调谐技术,对基于掺氧化镁周期性极化铌酸锂晶体（MgO:LiNbO3, PPMgLN）准相位匹配（QPM）的全固态连续波（CW）光学参量振荡器（OPO）宽波段无分立连续调谐输出特性进行研究。实验采用连续工作模式和外腔结构,基于多周期PPMgLN晶体的30.2,30.4和30.6 m周期,在改变晶体的极化周期的基础上,同时在30～100 ℃范围内调节晶体工作温度。实验结果表明：CW PPMgLN OPO的泵浦阈值仅为0.22 W;不同极化周期需要的温度调谐范围不同;信号光在1 559.8～1 597.2 nm近红外波段和闲频光在3 187.3~3 347.3 nm中红外波段连续调谐输出。实现了外腔式全固态CW OPO在信号光和闲频光波段的无分立连续调谐输出。     

4-乙酰基吡啶红外和拉曼光谱的密度泛函理论研究

4-乙酰基吡啶是一种重要的添加剂和医药中间体。在室温条件下使用液膜法测定了4-乙酰基吡啶的红外光谱和拉曼光谱,结合密度泛函理论在高水平基组条件下计算得到的稳定构型、振动频率和各谱带的势能分布,对观测到的谱带做出了全面指认和详细分析,为该类化合物的实验鉴别提供了理论依据。     

Spectroscopy of Laser Plumes for Atto‐Mole and ng/g Elemental Analysis

Abstract

Two all‐optical analytical techniques are reviewed. Both are capable of highly sensitive multi‐element analysis. One is by means of resonance‐enhanced plasma spectroscopy. It minimizes the continuum background associated with laser‐induced plasmas. Relative to laser‐induced breakdown spectroscopy, the signal‐to‐noise ratio is improved by orders of magnitude, thus allowing the quantitation of sodium and potassium at the single blood cell level. The other technique utilizes laser‐excited atomic fluorescence. It has been traditionally handicapped by its one wavelength–one transition specificity. We showed, however, that numerous elements could be induced to fluoresce at a single excitation wavelength of 193 nm provided that the analytes were imbedded in dense plumes, such as those produced by pulsed laser ablation. This method eliminates the continuum plasma background and sub‐ppb sensitivity was demonstrated in the analysis of aqueous lead colloids.     

Pressure Effects on Spectra of Tunable Laser Crystal GSGG:Cr3+ I: Theory

A theory for shifts of energy spectra due to electron-phonon interaction (EPI) has been developed. Both thetemperature-independent contributions and the temperature-dependent ones of acoustic branches and optical brancheshave been derived. It is found that the temperature-independent contributions are very important, especially at lowtemperature. The total pressure-induced shift (PS) of a level (or spectral line or band) is the algebraic sum of its PSwithout EPI and its PS due to EPI. By means of both the theory for shifts of energy spectra due to EPI and the theoryfor PS of energy spectra, the total PS of R1 line of tunable laser crystal GSGG:Cr3+ at 70 K as well as the ones of itsR1 line, R2 line and U band at 300 K will be successfully calculated and explained in this series of papers.