环境光对谷氨酸钠溶液激光拉曼光谱的影响

探讨了环境光的存在,对谷氨酸钠溶液的激光拉曼光谱的影响。研究表明,不同的环境光,自然光和室内荧光灯光,会对拉曼光谱产生不同的干扰效应,存在着特征谱峰、负峰或尖锐正峰, 干扰的影响不能忽略。建议在进行溶液激光拉曼光谱检测时,需在暗室或暗罩中进行,以完全隔离环境光的影响。     

Pulsed alkali pump light sources for Nd:YAG lasers

Pulsed arc discharges in alkali metal vapours are investigated for use as pump light sources for Nd:YAG lasers. Alkali lamps have a very high radiation efficiency and emit strong lines near the laser pump bands. These absorption bands are fitted by the emission spectrum of sodium and potassium lamps by changing the vapour pressure and input power. The spectral radiation distributions of the lamps are measured by a spectrograph with a gated OMA system. Ray tracing calculations for a laser cavity are used to evaluate the efficiency of the alkali radiation emission for Nd:YAG pumping. The results show that the excitation efficiency of the alkali lamps is twice as high as that of usually used rare gas lamps. For sodium resonance lines the side-on spectral radiance is calculated by a radiation transport model to estimate the pressure and the temperature profile. The results indicate that the alkali vapour lamps could be used as pump light sources with high efficiencies and low heat loading of the laser cavity.     

谷氨酸钠溶液514nm激光拉曼光谱受环境光影响的研究

探讨了环境光的存在对谷氨酸钠溶液的514 nm绿色激光激发的拉曼光谱的影响.研究表明不同的环境光、自然光和室内荧光灯光均会对514 nm激光拉曼光谱产生干扰,存在着特征干扰峰.自然阳光干扰较小;而荧光灯光表现为1127、2107 cm-1和2170 cm-1等3个明显尖锐的脉冲峰,不能忽略.建议在进行谷氨酸钠溶液514 nm绿色激光拉曼光谱检测时,须在暗室或暗罩中进行,以完全隔离环境光的影响.     

环境光对谷氨酸钠溶液近红外激光拉曼光谱的影响

探讨了环境光,对谷氨酸钠溶液的近红外激光拉曼光谱的影响。研究表明不同的环境光,自然光和室内荧光灯光,均会对近红外拉曼光谱产生不同的干扰效应,存在着特征谱峰,倒峰或尖锐正峰。虽干扰表现不同,但都有影响,不能忽略。建议在进行溶液近红外激光拉曼光谱检测时,须在暗室或暗罩中进行,以完全隔离环境光的影响。     

Solid-state laser system for laser cooling of sodium

We demonstrate a frequency-stabilized, all-solid laser source at 589 nm with up to 800 mW output power. The laser relies on sum-frequency generation from two laser sources at 1064 nm and 1319 nm through a PPKTP crystal in a doubly resonant cavity. We obtain conversion efficiencies as high as 2 W/W² after careful optimization of the cavity parameters. The output wavelength is tunable over 60 GHz, which is sufficient to lock on the sodium D₂ line. The robustness, beam quality, spectral narrowness and tunability of our source make it an alternative to dye lasers for atomic physics experiments with sodium atoms.     

Ion-implanted target for soft x-ray laser investigations

Ion-implantation has been used to make a target suitable for the investigation of soft X-ray laser action via resonant photo-pumping. Neon was implanted on one side of a thin aluminum foil and sodium fluoride was coated on the other side. A 100 picosecond laser pulse at 2 × 10¹⁴ W cm^-2was used to irradiate the neon side, and 330 ps later the sodium fluoride side was irradiated with a similar pulse. X-ray spectroscopy was used to measure the state of ionisation of the neon, and the inferred electron temperature was compared with a one-dimensional computer simulation. The spectral brightness of the pumping radiation was also estimated.     

Flame locking of dye lasers to atom lines

Frequency locking of N₂-laser-pumped, flash-pumped and continuous-wave dye lasers near the non-inverted 3S-3P Na atom transitions is obtained by placing sodium vapor produced in a flame inside the untuned dye laser cavity. Several possible causes for the spectral condensation of the dye emission are suggested.     

Excitation mechanisms and spectral shape of the diffuse violet emission band in Na2

A dense sodium vapour (T=450°C) has been illuminated with a laser light tuned across the whole visible region. For any laser wavelength the diffuse violet band of Na₂ molecule (peaking at 436.5 nm) has been found in fluorescence spectrum. Several mechanisms are proposed for excitation of the diffuse band, including collisional energy transfer and ionization-recombination processes. New observations of a spectral shape of the diffuse band are reported.     

Molecule formation and energy transfer processes in a vapor with high density of 3P-excited sodium atoms

A rich fluorescence spectrum extending between 4000 and 8200 Å has been observed whenever sodium vapor is excited by dye laser light tuned to the 3²S → 3²P transition. Molecule formation due to collisions between excited and unexcited atoms is manifested by the presence of an emission band of sodium in the spectral range 4160–4570 Å.     

宏-微脉冲激光激发钠信标回波光子数的数值计算与探讨

当采用低功率的宏-微脉冲激光激发钠信标时, 尽管激光传输和钠信标光斑大小受到大气湍流影响, 但是钠信标具有回波光子数无起伏且激发品质因数高的优点. 除此之外, 宏-微脉冲激光激发钠信标还与激光的宏脉冲线型有关. 对于高斯线型的宏脉冲, 增大微脉冲的宽度有利于提高激发钠信标的品质因数和激发态概率. 为了获得更多的钠信标回波光子和较小的钠信标半径, 增大激光功率的同时要考虑良好的光束质量、适当的激光发射口径以及光谱宽度等影响因素. 因此, 优选宏-微脉冲激光的参数、发射口径、发射方式等对于激发优良特性的钠信标有着重要的现实意义.     

合成双分子膜三元体系的激发态能量转移

在４ （４’ 癸氧基 ４ 氧基联苯）丁基三甲基溴化铵双分子膜体系内,通过静电相互作用使达旦黄、荧光黄和四苯基卟啉磺酸阴离子键合在囊泡表面;研究了达旦黄给体通过荧光黄传递到四苯基卟啉磺酸阴离子受体的三元激发态能量转移。能量转移的结果改善了光的输出,扩展了光波的输出范围。     

Resonant Scattering of Picosecond Laser Pulses by Atoms in Alkali Metal Vapors

Resonant scattering of ultrashort laser pulses (ULPs) in the vicinity of spectral doublets in monatomic lithium and sodium vapors is studied theoretically. The scattering probability over the entire time of pulse action is calculated as a function of various parameters of the problem (carrier frequency and ULP duration, as well as vapor pressure and temperature). It is shown that the dependence of the total scattering probability on the pulse duration is generally nonlinear by nature.     

Spectral analysis of a laser beam

The formulas of the dependence of the spectral laser power distribution and its spectral half-width on the physical parameters of its laser active medium are derived. In addition it is found that, if the gain line profile has a Lorentzian or Gaussian distribution, the spectral laser power distribution is of a Lorentzian profile. The spectral halfwidth of the laser beam in both cases are slightly different form each other. For a general gain line profile, the spectral laser power distribution behaves as a differential form like that of the gain line profile.The spectral halfwidth of He/Ne laser beam having powers (0·5 mW, 1·0 mW, 3·0 mW and 50 mW) and that of their longitudinal modes, the laser gain factor and the difference between the population atomic densities of the upper and lower energy levels for the laser line transition are experimentally determined.     

Effect of the laser axial modes on the coherence length of the laser beam

The effect of the presence of the axial modes within the spectral halfwidth of a laser spectral line on the visibility of its interference fringes is represented. It is found in case of axial modes with equal spectral halfwidths that the dominant factor in determining the coherence length of the laser beam is the spectral halfwidth of its axial mode and not the spectral halfwidth of the laser line. For the case of a laser beam with axial modes of different spectral halfwidths, the calculation shows a coherence length, closer to the mode with the smaller halfwidth.     

Probe Raman spectroscopy of sodium uranyl-acetate microcrystals

The technique for recording Raman spectra in uranium compounds using a probe minispectrometer with a multielement radiation detector has been developed. A selective filter, which reflects exciting laser radiation and transmits Raman signals, has been used to suppress the exciting radiation. It is shown that the technique developed makes it possible to record Raman spectra from a small amount (~10^–5 g) of sodium uranyl-acetate polycrystals in a wide spectral range for several seconds.     

Characteristics of whispering-gallery-mode dye lasers utilizing dye-doped solid microspheres by UV N2-laser pumping

The characteristics of a whispering-gallery-mode (WGM) dye laser using a variety of dye-doped solid microspheres, pumped by a UV N₂-laser, are presented. Experimental results for the WGM dye laser are presented with the spatial distribution and spectral and temporal responses of lasing. The spectral response of a new variety of WGM dye laser is in the blue-green or red spectral regions, and over a wide spectral range.     

变形镜对千赫兹掺钛蓝宝石飞秒激光频谱相位补偿

尝试用光谱展宽的方法从频谱相位(而非时域相位)的角度利用变形反射镜来补偿1kHz飞秒激光系统输出光路的频谱相位畸变,从而提高飞秒激光脉冲的时域强度衬比度,改善其光束质量。频谱相位补偿实验是在一台1kHz掺钛蓝宝石飞秒激光系统输出光路中,针对超短脉冲光束通过传输介质后的频谱相位畸变,引入变形反射镜进行补偿。应用频谱相位干涉直接电场重构(SPIDER)方法和仪器作为测量手段,建立了一套相位测量补偿系统。实验结果表明用变形反射镜可使激光脉冲的相位畸变得到较好的补偿,脉冲的光束质量得到改善。这种方法的主要思想就是将相位补偿转换为空问的光程控制,控制简单且损耗很低,是自适应光学中具有应用前景的一种补偿方法。     

Piecewise adiabatic passage with a series of femtosecond pulses

We develop a method of executing complete population transfers between quantum states in a piecewise manner using a series of femtosecond laser pulses. The method can be applied to a large class of problems as it benefits from the high peak powers and large spectral bandwidths afforded by femtosecond pulses. The degree of population transfer is robust to a wide variation in the absolute and relative intensities, durations, and time ordering of the pulses. The method is studied in detail for atomic sodium where piecewise adiabatic population transfer, as well as the induction of Ramsey-type interferences, is demonstrated.     

高功率激光装置输出光束相对光谱功率测量方法

针对SILEX-I超短超强脉冲激光装置输出光束光谱分布的精密测量问题,采用脉冲激光相对光谱功率来评价光谱分布,以溴钨灯为标准光源开展相对光谱功率测量方法的研究,获得相对光谱功率的理论计算公式。以SP2760光栅光谱仪作为光谱测量设备在SILEX-I激光装置上进行了光谱分布测量的验证实验,并给出了不确定度评定,获得了扩展相对不确定度1.7%的测量精度。测量结果显示,相对光谱功率分布与光栅光谱仪的原始光谱响应值分布具有显著的差异,可以更加准确地反映输出脉冲的光谱分布。     

光谱测量在激光加工在线监测上的应用研究进展

随着现代工业的发展,复杂加工环境和对象、大动态范围、高效率和高精度激光加工需求愈加迫切,在线监测并实时优化激光加工参数是一条重要的解决途径。与此同时,激光与物质相互作用时可产生与加工参数、加工过程和目标特性密切相关的光信号和表面光学特性变化,在线测量光信号光谱可分析加工过程和状态,故光谱测量有望成为一种重要的激光加工在线监测手段。实际上,光谱测量已应用于激光焊接、激光切割和钻孔、激光清洗打磨、微纳结构制备和增材制造等几乎所有激光加工工艺,具有分辨率高和光谱信息丰富等特点。分析和总结了用于激光加工在线监测的光谱测量技术,包括等离子体光谱、反射光光谱和非线性光信号光谱等。基于单脉冲和多脉冲激光加工激发等离子体信号的光谱测量,除实现化学成分定性和定量监测外,还可以根据特征谱线相对强度变化实时调焦,根据等离子体温度监测和调控激光加工过程中与热效应相关的物理过程;作为一种无损伤且工作距离较远的监测方法,反射光光谱监测可通过测量特定波段反射光信号光谱积分功率、特征谱线和波段位置和强度来有效监测材料表面清洁度、损伤、色度和成分变化等;而在特定条件下产生的谐波信号、荧光信号和拉曼信号等非线性光信号,尽管应用场景有限,但提供了一种实现成分、焦距和材料损伤等监测的新方法。进而,展望了光谱测量在激光加工在线监测上应用的未来发展趋势,包括多种光信号的光谱协同监测与光、声、温度及图像等多种信号测量的复合监测。同时,人工智能技术与在线监测和激光加工的深入结合将进一步推动激光加工技术的智能化发展。