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Doubled femtosecond laser pulses in-line are needed in the collinear pump-probe technique, collinear second harmonic generation frequency-resolved optical gating (SHG FROG) and the spectral phase interferometry for direct electric-field reconstruction (SPIDER), etc. Normally, it is generated by using a Michelson's structure. In this paper, we proposed a novel structure with two-layered reflective Dammann gratings and the reflective mirrors to generate doubled femtosecond laser pulses in line without transmission optical elements. Angular dispersion and spectral spatial walk-off are both compensated. In addition, this structure can also compress the positive chirped pulse, which cannot be realized with a Michelson's structure. By adopting triangular grating and blazed gratings, the efficiency of the system would in principle be increased as the Michelson's scheme. Experiments demonstrated that this method should be an alternative approach for generation of the double compressed pulses of femtosecond laser for practical applications. 相似文献
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A.K. Sharma R.K. Patidar M. Raghuramaiah P.A. Naik P.D. Gupta 《Optics Communications》2011,284(19):4596-4600
A simple technique is presented to generate temporally flat-top shaped laser pulses using electro-optic modulator (Pockels cell). It involves splitting of input laser pulse into two halves of equal intensity and then stacking together with appropriate optical delay to get a temporally flat-top laser pulse. It also allows generation of other pulse shapes by varying the relative intensity, delay, and phase between two halves of the input laser pulse. Temporally flat-top laser pulses of duration ~ 9 ns have been generated using ~ 7 ns duration incident laser pulses from a flash lamp pumped Q-switched Nd:glass laser oscillator. The rise and fall-time of the shaped pulse is limited by speed of electro-optic switch (Pockels cell), which is ~ 2 ns in the present case. 相似文献
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Flexible gratings embedded in poly-dimethlysiloxane (PDMS) were fabricated using femtosecond laser pulses. Photo-induced gratings in a flexible PDMS plate were directly written by a high-intensity femtosecond (130 fs) Ti: Sapphire laser (λp=800 nm). Refractive index modifications with 4 μm diameters were photo-induced after irradiation of the femtosecond pulses with peak intensities of more than 1×1011 W/cm2. The graded refractive index profile was fabricated to be symmetric around the center of the focal point. The diffraction efficiency of the grating samples is measured by an He-Ne laser. The maximum value of refractive index change (Δn) in the laser-modified regions was estimated to be approximately 3.17×10−3. 相似文献
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Based on the modified Kogelnik diffraction efficiency equation, the diffraction intensity spectrum and the total diffraction efficiency of volume gratings in photorefractive media are studied systematically. Taking photorefractive InP:Fe crystal as an example, the effect of the grating parameters and the pulse width on the diffraction properties are presented, in particular under the influence of crystal material dispersion. Under the combined effects, the diffraction pulse profiles and the total diffraction efficiency are shown. Also, the diffraction properties with and without crystal material dispersion are compared. These studies indicate that the properties of the diffraction beams can be controlled by the holographic grating parameters; this property can be used for pulse shaping applications. 相似文献
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Nonlinear X-wave formation at different pulse powers in water is simulated using the standard model of nonlinear Schrödinger equation (NLSE). It is shown that in near field X-shape originally emerges from the interplay between radial diffraction and optical Kerr effect. At relatively low power group-velocity dispersion (GVD) arrests the collapse and leads to pulse splitting on axis. With high enough power, multi-photon ionization (MPI) and multi-photon absorption (MPA) play great importance in arresting the collapse. The tailing part of pulse is first defocused by MPI and then refocuses. Pulse splitting on axis is a manifestation of this process. Double X-wave forms when the split sub-pulses are self-focusing. In the far field, the character of the central X structure of conical emission (CE) is directly related to the single or double X-shape in the near field. 相似文献
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利用傅里叶模式理论分析了TE波自准直角入射的使用条件下,多层介质膜光栅的光栅区和多层膜区电场分布的特点.分别讨论了HfO2和SiO2为顶层光栅材料时,光栅结构参数对光栅脊峰值电场的影响,结果表明,对于不同膜厚的顶层材料,存在一个最佳膜厚度,使光栅脊峰值电场最小,并且当膜厚增大时,设计大高宽比的光栅可以降低该电场峰值.最后,在大角度条件下使用多层膜光栅也可以降低光栅脊处的峰值电场.
关键词:
衍射光学
多层介质膜光栅
模式理论
损伤阈值 相似文献
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采用HPM溶液(盐酸、双氧水和去离子水的混合液)结合氧等离子体对多层介质膜脉宽压缩光栅进行清洗研究。用X射线光电子能谱检测光栅表面的元素成分及其原子含量的变化。实验结果表明,氧等离子体处理能有效去除光栅表面残留光刻胶和碳氟化合物; 再经HPM溶液清洗,反应离子束刻蚀和氧等离子体处理过程产生的金属污染物被进一步去除。经过上述清洗工艺处理后,光栅一级衍射效率仍保持在95%以上,光栅表面激光诱导损伤阈值达到1.6 J/cm2 (1053 nm, 10 ps)。实验结果说明了氧等离子体和HPM溶液相结合能有效清洗多层介质膜脉宽压缩光栅,并显著提高光栅损伤阈值。 相似文献
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为了提高HfO2顶层多层介质膜脉宽压缩光栅(PCG)的抗激光损伤性能,使用Piranha溶液(浓硫酸和双氧水的混合液)清洗PCG去除其制作工艺和使用过程中残留在表面的污染物,包括CHF3作为工作气体对HfO2进行反应离子束刻蚀生成的碳氟化合物及金属氟化物。对Piranha溶液的清洗温度、组成成分、清洗时间、清洗遍数等参数进行了系统研究,用扫描电子显微镜(SEM)观察清洗前后的PCG表面形貌,用X射线光电子能谱仪(XPS)检测清洗前后PCG表面的元素成分及其原子分数的变化,并分析了各残留污染物的去除机理。实验结果表明:Piranha溶液能有效去除PCG表面污染物,而且清洗温度越高,清洗遍数越多,对PCG表面残留污染物的去除效果越显著。在90 ℃下60 min有效活性时间内,使用浓硫酸和双氧水体积比为2∶1的Piranha溶液清洗3遍以上,PCG表面残留的F元素的原子分数接近0.1%(XPS的分辨极限),达到良好的清洗效果。 相似文献
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Shijie Liu Jianyong Ma Chaoyang Wei Zicai Shen Jianbin Huang Jianda Shao 《Optics Communications》2007,273(1):290-295
We present designs of high-efficiency compression grating based on total internal reflection (TIR) for picosecond pulse laser at 1053 nm. The setup is devised by directly etching gratings into the bottom side of a prism so that light can successfully enter (or exit) the compression grating. Dependence of the −1 order diffraction efficiencies on the constructive parameters is analyzed for TE- and TM-polarized incident light at Littrow angle by using Fourier modal method in order to obtain optimal grating structure. The electric field enhancement within the high-efficiency TIR gratings is regarded as another criterion to optimize the structure of the TIR gratings. With the criterion of high diffraction efficiency, low electric field enhancement and sufficient manufacturing latitude, TIR compression gratings with optimized constructive parameters are obtained for TE- and TM-polarized incident light, respectively. The grating for TE-polarized light exhibits diffraction efficiencies higher than 0.95 within 23 nm bandwidth and relatively low square of electric field enhancement ratio of 5.7. Regardless of the internal electric field enhancement, the grating for TM-polarized light provides diffraction efficiencies higher than 0.95 within 42 nm bandwidth. With compact structure, such TIR compression gratings made solely of fused silica should be of great interest for application to chirped pulse amplification (CPA) systems. 相似文献
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The ability to machine very small features in a material has a wide range of applications in industry. We ablated holes into thin film of 100 nm thickness made from various metals by femtosecond pulsed laser ablation. Using a Ti:Sapphire laser which supplies a laser pulse of 150 fs duration at central spectrum wavelength of 400 nm, we have produced a series sub-micron holes, whose diameters are less than 200 nm with a focused laser spot of 1.7 μm. We found that the material damage threshold has a great influence on the quality of the produced features. Experimental results shows that the heat-affected zone and the degree of being affected reduce with the increase of threshold value. 相似文献
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A simple method for generating multiple isolated femtosecond pulses by step gratings is presented, and a criterion for judging whether or not an incident pulse is just split into multiple independent pulses is obtained. The dependences of multiple pulses on the structural parameters of the step gratings are explored. The results show that an incident pulse can split into multiple isolated similar diffraction pulses for enough step height, and the pulse repetition interval increases with the increasing of the step height. 相似文献
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We built an atmosphere dispersion model of femtosecond laser pulses that can calculate temporal pulse width travelling in air. The initial pulse duration of 100 fs can be broadened to 60 ps when propagating 200 km in the atmosphere. An experimental system has been established to compensate the large dispersion propagating 200 km in the atmosphere. The single model fiber (SMF) and the prism pairs were, respectively, used for coarse and fine compensation in the system. The pulse duration was consistently regulated 150 fs by moving the distance of prism pairs. This method can reach submicron resolution for a long distance by means of time of flight measurement. 相似文献
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在大气环境下采用波长为800nm,脉宽为30fs的飞秒激光研究了Ni的双脉冲激光诱导击穿光谱,与单飞秒脉冲激光诱导击穿光谱相比,双飞秒脉冲在最优的双脉冲相对延时下,其信号强度增强接近10倍,实验研究了双脉冲相对延时在0-1300ps范围内不同延时对激光诱导击穿光谱信号强度增强因子的影响。整个相对延时区域可以分为三个阶段:在0-50ps区域内信号增强因子是一个持续增大的过程,在50ps左右,达到一个最大值;在50-300ps区域内,信号增强因子呈现出一个先下降后上升的过程;在300-1300ps,信号增强因子基本保持不变。 相似文献