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非线性系统的相空间重构可以将时间序列中蕴藏的信息充分地显露出来,其中时间延迟τ的选取具有十分重要的意义,同时这种选取也是很困难的。文章介绍了相空间重构中确定重构延迟时间τ的互信息法理论及其具体的计算方法,最终实际的数据证实了该算法的合理性。 相似文献
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利用光谱相位还原直接电场重建法对飞秒脉冲激光时域波形进行重建,分析了光谱测量波长示值误差和光谱辐照度示值误差对于飞秒脉冲光谱测量的影响。使用低压汞灯对光谱仪波长校准,根据校准结果,对测量光谱蓝移和红移,通过数值模拟研究波长示值误差对重建脉冲波形的影响;利用光谱辐射照度标准装置对光谱仪光谱辐照度校准,通过增加白噪声模拟分析和各种常用反射片实验测量研究光谱辐照度示值误差对重建脉冲波形的影响。结果表明,光谱测量波长示值误差和光谱辐照度示值误差对于飞秒脉冲光谱测量的相对标准差在1%之内。 相似文献
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飞秒激光诱导玻璃内Ba2TiSi2O8晶体的析出 总被引:1,自引:0,他引:1
使用聚焦后的800nm,150fs,250kHz的高重复频率飞秒脉冲激光器能够在BaO-TiO2-SiO2组分的玻璃内部三维选择性地诱导Ba2TiSi2O8晶体的析出. 发光光谱显示这种晶体把入射的800nm光转化成了400nm的蓝光,因此这种析出的晶体具有非线性倍频特性. 通过拉曼光谱测定,在当前的玻璃组分中析出的晶体是Ba2TiSi2O8. 研究表明,经250kHz的飞秒激光辐照一段时间后,在玻璃内部由于脉冲能量的连续沉积会使得激光辐照区域出现热积累效应,因此,该辐照区域的温度会不断升高以致超过玻璃析晶温度,最终诱导玻璃熔融析晶. 此外,对飞秒激光辐照区域不同部位进行拉曼光谱检测,结果表明:在整个区域Ba2TiSi2O8晶体的析出呈现中间比外围明显的分布特点,因此晶体析出与辐照形成的温度梯度场有密切关系. 相似文献
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半导体可饱和吸收镜(SESAM)在飞秒脉冲激光器锁模中,是一种非常有潜力的锁模启动器.其损伤闽值的高低与连续锁模阈值比较相近,极易损伤,因而研究在飞秒激光作用下SESAM的损伤阈值很有必要.利用飞秒激光分别对单晶硅、自然生长SESAM及腐蚀后SESAM在50fs、200fs和400fs脉宽下进行了表面烧蚀研究,并且保证每次烧蚀的激光脉;中个数为50个.结果发现单晶硅和自然生长SESAM的损伤阈值要高于腐蚀乓SESAM,随脉宽的增加而逐渐增大;而腐蚀后SESAM的损伤阈值却随脉宽的增加而逐渐减小. 相似文献
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随着飞秒光梳光谱、飞秒测距等飞秒激光器相关应用领域的发展,对于更高重复频率的飞秒激光器也产生了越来越迫切的需求。本文叙述了固体激光器和光纤激光器在产生GHz重复频率的飞秒脉冲输出上所使用的主要技术和技术进展,总结了GHz激光器的最新发展趋势。为之后进行GHz重复频率飞秒激光器研究的相关人员提供了一定的参考。 相似文献
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采用1kHz飞秒激光(脉宽148fs,中心波长775nm)对石英衬底的金膜的烧蚀过程进行了研究.单脉冲与多脉冲的烧蚀阈值可以通过烧蚀点的直径平方与所用的激光能流的关系曲线获得.通过累积能流和烧蚀脉冲数的关系,可以得到金膜的脉冲累积因子.采用飞秒激光加工材料的一些特点可以合理解释单脉冲阈值附近获得的一些实验现象. 相似文献
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Short pulses can induce high nonlinear excitation, and thus they should be favorable for use in multiphoton microscopy. However, the large spectral dispersion can easily destroy the advantages of the ultrashort pulse if there is no compensation. The group delay dispersion (GDD), third-order dispersion, and their effects on the intensity and bandwidth of second-harmonic generation (SHG) signal were analyzed. We found that the prism pair used for compensating the GDD of the two-photon microscope actually introduces significant negative high-order dispersion (HOD), which dramatically narrowed down the two-photon absorption probability for ultrashort pulses. We also investigated the SHG signal after GDD and HOD compensation for different pulse durations. Without HOD compensation, the SHG efficiency dropped significantly for a pulse duration below 20 fs. We experimentally compared the SHG and two-photon excited fluorescence (TPEF) signal intensity for 11 fs versus 50 fs pulses, a pulse duration close to that commonly used in conventional multiphoton microscopy. The result suggested that after adaptive phase compensation, the 11fs pulse can yield a 3.2- to 6.0-fold TPEF intensity and a 5.1-fold SHG intensity, compared to 50 fs pulses. 相似文献
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We demonstrate a simple method for complete characterization (of amplitudes and phases) of short optical pulses, using only a dispersive delay line and an oscilloscope. The technique is based on using a dispersive delay line to stretch the pulses and recording the temporal interference of two delayed replicas of the pulse train. Then, by transforming the time domain interference measurements to spectral interferometry, the spectral intensity and phase of the input pulses are reconstructed, using a Fourier-transform algorithm. In the experimental demonstration, mode-locked fiber laser pulses with durations of approximately 1 ps were characterized with a conventional fast photodetector and an oscilloscope. 相似文献
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We propose a scheme to generate isolated attosecond pulse using a linearly chirped two-color laser field, which includes a fundamental laser field and a weak infrared control laser field in the multicycle regime. The fundamental laser field consists of one linearly up-chirped and one linearly down-chirped pulses. The control pulse is chirped free. We compare the attosecond pulse generated in the chirped two-color field and the chirp-free field. It is found that an IAP can be generated even without carrier envelop phase stabilization in the chirped two-color laser field with a duration of 40 fs. We also discuss the influence of the relative intensity, relative phase, time delay, and chirping parameters on the generation of IAPs. 相似文献
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Willmann S Terenji A Busse H Yaroslavsky IV Yaroslavsky AN Schwarzmaier HJ Hering P 《Journal of the Optical Society of America. A, Optics, image science, and vision》2000,17(4):745-749
We have determined the scattering delay time of Mie scatterers (r = 255 nm quartz spheres in polyester resin) from a combination of steady-state (integrating-sphere) and time-resolved (frequency-domain) measurements performed in the multiple-scattering regime. The effective transport velocity of light was derived from intensity and phase measurements at four different wavelengths by using the time-integrated microscopic Beer-Lambert law. We could demonstrate a systematic underestimation of the effective transport velocity compared with the phase velocity in the medium. Assuming that this discrepancy was caused entirely by the transient nature of a single-scattering process, the data presented resulted in time delays of between 18 fs (lambda = 678 nm) and 177 fs (lambda = 1,064 nm) per scattering event. For three out of four wavelengths investigated, the measured values are in excellent agreement with values predicted by a theoretical model for the scattering delay time based on Mie theory. 相似文献
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A noncollinear second-harmonic-generation scheme that includes two gratings and a nonlinear optical crystal generates temporal solitons with a noncollinear phase mismatch and frequency-chirped laser pulses. At 180-fs pulse duration, 25-GW/cm2 fundamental intensity, -7647.3-m(-1) wave-vector mismatch, 66-fs delay time, and +/-3.07163 x 10(25) s(-2) frequency-chirp rates, temporal solitons with durations from 139 to 155 fs and Gaussian shapes can be obtained. The corresponding conversion efficiency is greater than 40%. 相似文献
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Finite size compression gratings in a large aperture chirped pulse amplification laser system 总被引:2,自引:0,他引:2
A simple model is presented to calculate the effects of the finite size of the diffraction gratings in the compressor of a chirped pulse amplification laser system. A wavelength-dependent clipping at the second grating alters the spectral distribution of the compressed pulses, affecting their time domain as well as their spatial distribution in the focal plane. Laser parameters of paramount importance to laser/plasma interaction experiments such as peak intensity, pulse duration, and prepulse levels are affected by the compressor design. Calculations of the effect of spectral clipping on these parameters for Gaussian, sech(2), and top-hat input spectra are discussed, and the benefit of double-pass compared with single-pass compression is also investigated. As an example, with 300-mm gratings and single-pass compression, for a sech(2) spectrum the pulse length of a 400-fs pulse increases to 459 fs, the peak intensity decreases by 25%, and the focal spot size increases by 8% because of the finite size of the gratings. 相似文献
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ROBERT SHELTON LONG-SHENG MA HENRY KAPTEYN MARGARET MURNANE JOHN HALL JUN YE 《Journal of Modern Optics》2013,60(3-4):401-409
Two independent mode-locked femtosecond lasers are synchronized to an unprecedented precision. The rms timing jitter between the lasers is 4.3 fs observed within a 160 Hz bandwidth over tens of seconds, or 26 fs within a 50 kHz bandwidth. Novel multi-stage phase-locked loops help to preserve this ultrahigh timing resolution while setting on arbitrary delay between the two pulse trains (0–5 ns). Under such synchronization, phase locking between the carrier frequencies of the two femtosecond lasers has been achieved. It is also demonstrated that the same level of synchronization can be achieved with two lasers at different repetition frequencies. 相似文献
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Abstract Picosecond phase conjugation and two-wave coupling in cerium-doped strontium barium niobate at 778 nm were studied. The phase conjugation reflectivity at 778 nm was measured to be R pc = 58%. It is close to that pumped by a continuous-wave pump source. The temporal width t pc and spectral width δγpc of the phase conjugate pulse were measured to be the same as that of the pump pulse. The intensity coupling gain of two-wave coupling as a function of time delay τD between two beams was also studied. 相似文献
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Third-harmonic generation (THG) in air in tight-focusing conditions is presented. Variation of the pulse duration supplied optimal conditions for THG by femtosecond pulses that varied in the range 110-1300 fs. We show that this third-harmonic generation was caused by Kerr-induced phase variations of fundamental and harmonic beams. Various characteristics (laser intensity, focusing conditions, pulse duration, air pressure, etc.) of THG in air were analyzed to optimize this process. The THG conversion efficiency of 795 nm, 300 fs radiation was 1 x 10(-3). The harmonic radiation did not show considerable disruption of its spectral and spatial distribution in tight focusing conditions for intensities as high as 5 x 10(14) W cm(-2). 相似文献
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Based on the refractive laser beam shaping system, the dark hollow femtosecond pulse beam shaping technique with a phase-only liquid crystal spatial light modulator (LC-SLM) is demonstrated. The phase distribution of the LC-SLM is derived by the energy conservation and constant optical path principle. The effects of the shaping system on the temporal properties, including spectral phase distribution and bandwidth of the femtosecond pulse, are analyzed in detail. Experimental results show that the hollow intensity distribution of the output pulsed beam can be maintained much at more than 1200 mm. The spectral phase of the pulse is changed, and the pulse width is expanded from 199 to 230 fs, which is caused by the spatial-temporal coupling effect. The coupling effect mainly depends on the phase-only LC-SLM itself, not on its loaded phase distribution. The experimental results indicate that the proposed shaping setup can generate a dark hollow femtosecond pulsed beam effectively, because the temporal Gaussian waveform is unchanged. 相似文献