共查询到20条相似文献,搜索用时 546 毫秒
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飞秒激光脉冲在传输过程中, 克尔自聚焦和等离子体散焦相互作用形成了长距离的自导光通道, 该过程称为飞秒激光成丝。飞秒激光成丝在火焰中诱导的荧光辐射为燃烧诊断提供了新的可能性, 为理解燃烧过程、提高燃烧效率和减少污染物的产生提供了有用的信息。针对飞秒激光成丝诱导的荧光辐射在燃烧诊断中的应用, 介绍了飞秒激光在火焰中的传输特性以及成丝动力学过程, 陈述了飞秒激光成丝诱导非线性光谱的机理及其在高温燃烧场诊断应用中的研究现状和进展, 探讨了当前飞秒激光成丝在该领域所面临的挑战和应用前景。 相似文献
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通过使用太赫兹(Terahertz,THz)时域光谱系统,探测从不同长度飞秒激光光丝辐射出的THz脉冲,观察到THz波在飞秒激光成丝过程中超光速传输的实验现象。进一步的分析表明:THz波在等离子体光丝区域的折射率小于其在空气中的折射率,这是使得THz波能够在成丝过程中超光速传输的主要原因。由此可以推测:THz脉冲极有可能是在等离子体光丝中进行导引传输的。最后,通过数值模拟获得了光丝区域内的THz本征模式,从而验证了上述推测。 相似文献
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自从第一次观察到飞秒激光大气成丝后,光丝备受科学家的关注。它的潜在应用价值主要包括电子加速、激光雷达远程遥感、太赫兹辐射和超短脉冲压缩。利用数值仿真的方法,通过改变艾里光束的衰减系数,研究了不同能量背景的环形艾里光束飞秒激光大气成丝特性,得到的光丝长度长于拥有相同峰值功率、弱能量背景高斯光束形成的光丝。通过分析飞秒激光光丝演化过程的时间和空间特性,发现了环形能量背景是环形艾里光束沿传播方向形成高能量密度光丝的前提条件。比较了环形艾里光束和高丝光束在成丝过程中的光谱展宽特性,发现不同衰减系数的环形艾里光束具有相似的光谱展宽特性,但要明显弱于高斯光束的光谱展宽。研究成果对与提升飞秒激光成丝效果具有参考意义。 相似文献
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Reed M.K. Steiner-Shepard M.K. Negus D.K. 《Quantum Electronics, IEEE Journal of》1995,31(9):1614-1618
A mode-locked Ti:sapphire regenerative amplifier system pumped with a single argon ion laser produces μJ energy femtosecond pulses of 800 nn wavelength at up to 300 kHz repetition rate. This output is used to generate tunable femtosecond pulses in the ultraviolet to as short as 240 mn by using a combination of harmonic generation, white-light continuum generation and parametric amplification. A variety of techniques to access different parts of the UV spectrum are presented 相似文献
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用Z-scan技术在532 nm的皮秒激光脉冲和800 nm飞秒激光脉冲作用下分别研究了ZnS晶体的非线性吸收及非线性折射特性。实验结果表明,ZnS晶体在532 nm的皮秒激光脉冲作用下非线性吸收为双光子吸收,其非线性吸收系数为5.310-11 m/W,在800 nm的飞秒激光脉冲作用下非线性吸收为三光子吸收,非线性吸收系数为0.5910-21 m2/W2;在532 nm皮秒激光脉冲作用下,ZnS晶体的非线性折射率符号为负,自由载流子产生的非线性折射率的改变占主导,而800 nm飞秒激光脉冲作用下,ZnS晶体的非线性折射率符号为正,束缚电子产生的非线性折射率的改变为主要因素。 相似文献
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Shah L. Tawney J. Richardson M. Richardson K. 《Quantum Electronics, IEEE Journal of》2004,40(1):57-68
Many recent investigations of micromachining with lasers, in vacuum and in ambient air environments, have demonstrated the improvements possible when using femtosecond-duration laser pulses compared with long laser pulses. There are obvious practical advantages for rapid micromachining in ambient air conditions. However, the maximum laser intensity and repetition rate are then eventually limited by the avalanche breakdown and nonlinear effects in the air through which the focused laser beam must propagate both outside the work piece and within the structure that is being machined. This paper investigates these limits in femtosecond deep hole drilling at high laser intensities in silicate glasses. In particular, it shows how nonlinear optical effects, particularly self-focusing, can dramatically affect hole shape and the rate of penetration during deep hole drilling. The experiments described here demonstrate how nonlinear Kerr focusing of femtosecond laser pulses occurs during propagation of intense femtosecond laser pulses through the atmosphere within the machined channel at powers levels significantly below the critical power for self-focusing in ambient air. 相似文献
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利用Z扫描测量技术研究了飞秒和皮秒激光脉冲激发下液体硝基苯的三阶非线性折射率n2。Z扫描实验的结果表明:液体硝基苯在20 ps、532 nm波长激发下的非线性折射率n2是300 fs,800 nm波长激发下的n2值的11倍。利用带相位物体的飞秒泵浦探测方法研究了液体硝基苯的非线性折射动力学机理。基于泵浦探测实验结果确定了液体硝基苯在超快激光激发后的非线性折射响应函数。测量结果可为基于硝基苯液体的集成光子学器件设计和溶液非线性测量提供有益参考 相似文献
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Femtosecond laser-tissue interactions: Retinal injury studies 总被引:1,自引:0,他引:1
Birngruber R. Puliafito C. Gawande A. Wei-Zhu Lin Schoenlein R. Fujimoto J. 《Quantum Electronics, IEEE Journal of》1987,23(10):1836-1844
We report the first study of laser-tissue interaction in the femtosecond time regime. Retinal damage thresholds and mechanisms produced by exposure to high-intensity femtosecond laser pulses were investigated in chinchilla grey rabbits. Exposures were performed using single laser pulses of 80 fs duration at 625 nm. ED50 injury thresholds of 0.75 and 4.5 μJ were measured using fluorescein angiographic and ophthalmoscopic visibility criteria evaluating 204 laser exposures. Ultrastructural studies including light and electron microscopy were performed on selected lesions. Results suggest that the primary energy deposition in the retina occurs in melanin, However, in contrast to laser injuries produced by longer pulses, exposures of more than 100 × threshold in the50-100 mu J range did not produce significantly more severe lesions or hemorrhage. This suggests the presence of a nonlinear damage limiting mechanics in tissue exposed to femtosecond laser pulses. 相似文献
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Kibler B. Fischer R. Lacourt P.-A. Courvoisier F. Ferriere R. Larger L. Neshev D.N. Dudley J.M. 《Electronics letters》2007,43(17):915-916
Optimised compression of femtosecond fibre laser pulses in highly nonlinear fibre is demonstrated. Specifically reported are compressed pulse durations below 30 fs using a simple setup where a single sub-10 cm segment of highly nonlinear fibre is directly spliced to the output pigtail of a commercial femtosecond fibre laser. The compressed pulse quality is confirmed through frequency resolved optical gating measurements. 相似文献
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《Quantum Electronics, IEEE Journal of》1989,25(7):1704-1707
Synchronized femtosecond and tunable picosecond laser pulses have been generated using a linear cavity configuration in both lasers. The long-term stability of the synchronization, as well as the frequency of the synchronously pumped femtosecond dye laser, is assured by active stabilization of the cavity length. Additionally, the picosecond and femtosecond pulses have been amplified in dual amplifier chains to pulse energies in the microjoule range at a 1 kHz repetition rate. The total peak intensity available for two-photon, nonlinear excitations is on the order of 109 times greater than that available from unamplified beams 相似文献
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The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm-2,we findβ=3.5 cm GW-1 at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τe~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λp=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm. 相似文献
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高能量低重复频率超短激光脉冲的测量 总被引:2,自引:0,他引:2
利用非线性晶体 (BBO)的非共线匹配倍频效应 ,研制了实时测量高能量低重复频率超短激光脉冲宽度的单脉冲自相关仪 ,并对飞秒 (fs)参量放大器的输出脉冲宽度进行了测量 ,测得了 10 3fs的超短激光脉冲宽度。 相似文献