共查询到19条相似文献,搜索用时 57 毫秒
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液晶空间光调制器的离散型相位调制和像素间隙是4f脉冲整形系统的主要失真原因,基于以上因素的分析,建立了完善的4f脉冲整形系统数学模型,数值模拟了不同相位调制变化率、不同像元尺寸、不同间隙尺寸以及不同色散关系下的离散型相位调制和像素间隙导致的失真情况。模拟结果表明:离散型相位调制会导致整形脉冲中出现副本脉冲,相位调制变化率越大或像元尺寸越大均会导致这种副本脉冲越强,输出目标脉冲失真越严重;像素间隙也会导致整形脉冲中出现副本脉冲,间隙尺寸越大会导致这种副本脉冲越强,输出目标脉冲失真越严重;两种副本脉冲均呈等间隔分布,其周期由每个像元对应的频谱宽度决定,非线性光谱色散会使副本脉冲啁啾化且强度变小。 相似文献
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液晶空间光调制器的离散型相位调制和像素间隙是4f脉冲整形系统的主要失真原因,基于以上因素的分析,建立了完善的4f脉冲整形系统数学模型,数值模拟了不同相位调制变化率、不同像元尺寸、不同间隙尺寸以及不同色散关系下的离散型相位调制和像素间隙导致的失真情况。模拟结果表明:离散型相位调制会导致整形脉冲中出现副本脉冲,相位调制变化率越大或像元尺寸越大均会导致这种副本脉冲越强,输出目标脉冲失真越严重;像素间隙也会导致整形脉冲中出现副本脉冲,间隙尺寸越大会导致这种副本脉冲越强,输出目标脉冲失真越严重;两种副本脉冲均呈等间隔分布,其周期由每个像元对应的频谱宽度决定,非线性光谱色散会使副本脉冲啁啾化且强度变小。 相似文献
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在较全面地给出光栅对脉冲整形器失调产生附加相位项表达式的同时,详细地讨论了展宽器失调的附加相位放大系统传输过程中的变化,并与压缩器失调特性作了比较,分析了这些失调对超高亮度激光系统输出脉冲及其聚焦场时间特性的影响,得到了确定光栅对脉冲整形器失调容限的基本原则。 相似文献
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推导了光栅对压缩器两光栅在垂直于刻线的平面(衍射面)内有一夹角时1至4阶色散变化量的表达式,以及脉冲超高斯光束经光栅对压缩后的场分布。并据此模拟分析了光栅表面平行性失调对输出脉冲时空特性的影响。结果表明:脉冲光束单次通过光栅对时其波形会产生扭曲,光栅对的失调会使脉冲扭曲更加严重;而两次通过光栅对时横向谱移动的影响会消除,但脉冲将出现旁瓣,光栅对的失调使得脉冲在时间上提前,且色散阶数越高色散变化量对压缩脉冲时空特性的影响越大。 相似文献
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研究了不同腔镜结构不同失调情况对空间谐振式激光陀螺中光束空间位置的影响.利用Collins积分与Collins程函理论以及MATLAB软件工具,对腔镜失调前后激光陀螺中光束传输进行了仿真计算.结果表明,相同失调量的不同反射镜所产生的拍频频差是不同的,且分别从M1和M4镜探测到的拍信号频不相同|对于小增益激光器,使用球面镜的腔镜结构较平面镜的腔镜结构更易形成稳定光束空间位置分布|由所计算的空间坐标xn可以看出,双向行波光束的光斑中心发生了偏移,在一定的失调量下将会影响到激光陀螺的拍频输出.研究结果对激光陀螺的工程检测和腔镜调整有指导作用,有助于激光陀螺测量准确度的提高. 相似文献
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飞秒激光成丝超连续辐射具有高强度和高时空相干性等优点,作为一种超宽带光源在很多领域都具有广泛的应用前景.本文提出一种结合微透镜阵列的空间调制和基于液晶空间光调制器的时域整形的飞秒激光脉冲整形方式,利用基于遗传算法的反馈优化控制,实现了飞秒激光在熔融石英中成丝产生的超连续辐射强度的调制,得到了在一定范围内光谱强度可控的超连续辐射光谱;光谱的能量密度可以从0.03μJ/nm调制到0.09μJ/nm,其能量密度变化达到了初始值的3倍.计算了典型迭代代数对应的整形脉冲时域包络,分析了超连续光谱随迭代代数的演化趋势,结果表明,脉冲包络的峰值强度和波形分布是影响超连续光谱展宽和强度的主要物理原因. 相似文献
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This paper describes the generation of shaped femtosecond multiple pulses by using the phase-only Dammann filters in 4f femtosecond shaper and gives the experimental result of femtosecond pulse characterization by the frequency- resolved optical gating (FROG) technique. With the theoretical simulation, it concludes that the quality of the generated output array is relevant to the number of pixels and the spacing between the components.[第一段] 相似文献
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Under classical particle dynamics, the interaction process between intense femtosecond laser pulses and icosahedral noble-gas atomic clusters was studied. Our calculated results show that ionization proceeds mainly through tunnel ionization in the combined field from ions, electrons and laser, rather than the electron-impact ionization. With increasing cluster size, the average and maximum kinetic energy of the product ion increases. According to our calculation, the expansion process of the clusters after laser irradiation is dominated by Coulomb explosion and the expansion scale increases with increasing cluster size. The dependence of average kinetic energy and average charge state of the product ions on laser wavelength is also presented and discussed. The dependence of average kinetic energy on the number of atoms inside the cluster was studied and compared with the experimental data. Our results agree with the experimental results reasonably well. 相似文献
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Time-dependent density functional theoretical studies on the photo-induced dynamics of an HCI molecule encapsulated in C60 under femtosecond laser pulses 下载免费PDF全文
By using first-principles simulations based on time-dependent density functional theory, the chemical reaction of an HCl molecule encapsulated in C60 induced by femtosecond laser pulses is observed. The H atom starts to leave the Cl atom and is reflected by the C60 wall. The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H-Cl bond axis are investigated. The radial oscillation is also found in the two polarization directions of the laser pulse. The relaxation time of the H-Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization. Those results are important for studying the dynamics of the chemical bond at an atomic level. 相似文献
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Time-dependent density functional theoretical studies on the photo-induced dynamics of an HCl molecule encapsulated in C_(60) under femtosecond laser pulses 下载免费PDF全文
By using first-principles simulations based on time-dependent density functional theory,the chemical reaction of an HCl molecule encapsulated in C60induced by femtosecond laser pulses is observed.The H atom starts to leave the Cl atom and is reflected by the C60wall.The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H–Cl bond axis are investigated.The radial oscillation is also found in the two polarization directions of the laser pulse.The relaxation time of the H–Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization.Those results are important for studying the dynamics of the chemical bond at an atomic level. 相似文献
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Christian SymietzErhard Lehmann Renate GildenhaarRobert Koter Georg BergerJörg Krüger 《Applied Surface Science》2011,257(12):5208-5212
Bone implants made of metal, often titanium or the titanium alloy Ti6Al4V, need to be surface treated to become bioactive. This enables the formation of a firm and durable connection of the prosthesis with the living bone. We present a new method to uniformly cover Ti6Al4V with a thin layer of ceramics that imitates bone material. These calcium alkali phosphates, called GB14 and Ca10, are applied to the metal by dip coating of metal plates into an aqueous slurry containing the fine ceramic powder. The dried samples are illuminated with the 790 nm radiation of a pulsed femtosecond laser. If the laser fluence is set to a value just below the ablation threshold of the ceramic (ca. 0.4 J/cm2) the 30 fs laser pulses penetrate the partly transparent ceramic layer of 20-40 μm thickness. The remaining laser fluence at the ceramic-metal interface is still high enough to generate a thin metal melt layer leading to the ceramic fixation on the metal. The laser processing step is only possible because Ti6Al4V has a lower ablation threshold (between 0.1 and 0.15 J/cm2) than the ceramic material. After laser treatment in a fluence range between 0.1 and 0.4 J/cm2, only the particles in contact with the metal withstand a post-laser treatment (ultrasonic cleaning). The non-irradiated rest of the layer is washed off. In this work, we present results of a successful ceramic fixation extending over larger areas. This is fundamental for future applications of arbitrarily shaped implants. 相似文献
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利用飞秒脉冲激光沉积法在n-Si(100)单晶衬底上制备了ZnO薄膜, 分析了衬底温度、激光能量、氧压及退火处理对薄膜结构和光学性能的影响. X射线衍射结果表明, 当激光能量为15?mJ、氧压为10?mPa时, 80?℃生长的薄膜取向性最好. 场扫描电子显微镜结果显示薄膜的晶粒尺寸随激光能量的增加而减小、随衬底温度的升高而增大且退火后明显变大. 紫外-可见透射光谱显示薄膜具有90%以上的可见光透过率.光致发光谱表明当氧压为10 mPa时,除了ZnO的紫外本征峰外, 还有一波长为410 nm的强紫光峰, 当氧压增至20 mPa以上, 所有缺陷峰均消失, 只有376 nm处的紫外本征峰. 与纳秒激光法所制备的薄膜特性进行了比较, 结果表明, 虽然纳秒激光沉积所制备的薄膜具有更高的c轴取向度, 但飞秒激光沉积制备的薄膜具有更好的发光性能.
关键词:
氧化锌
飞秒脉冲激光沉积
透过率
光致发光 相似文献