共查询到20条相似文献,搜索用时 156 毫秒
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利用纳米粒子辅助对飞秒激光能量进行空间局域化,使其在基底表面诱导产生纳米尺度的近场增强,这对超衍射极限微结构加工具有重要意义.目前对于粒子阵列诱导飞秒激光纳米孔加工的研究仅限于金属Au粒子及低折射率聚苯乙烯介电粒子等,本文提出并开展了应用高折射率TiO_2介电粒子阵列作为辅助诱导激光近场增强从而进行飞秒激光超衍射纳米孔加工的研究.对TiO_2介电粒子阵列在Si,Pt及SiO_2表面的近场强度分布进行了数值模拟,研究其基底表面近场增强的规律及物理过程.研究结果发现,使用硅基底时,阵列与单一TiO_2球形粒子相比其近场增强仅下降约30%;相对于入射激光强度而言,在直径约为100nm的空间范围内获得140倍的近场增强,这一现象可用于百纳米孔的激光加工.同时在其他典型基底的理论计算结果中也表明,几乎在所有金属及介电材料表面均可以实现良好的百纳米空间范围内的近场增强,并且具有近场随着基底折射率变大而增强的规律.这些现象的产生归因于TiO_2粒子中磁四极振荡产生的激光前向场增强及粒子与基底的耦合作用.进一步引入镜像电荷模型对基底光学参数对其表面近场增强的影响规律进行了分析和解释.本文的模拟结果对飞秒激光近场超衍射极限纳米加工的应用有着重要的意义. 相似文献
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相因子判断法分析菲涅耳波带片的衍射场 总被引:1,自引:0,他引:1
基于波前相因子判断法,并考虑到波带片孔径的影响,揭示了波带片的衍射场所含基元成分及各成分在衍射场的积分表达式,并导出了沿轴的衍射场振幅分布公式及沿轴的振幅分布曲线,得到多个实焦斑的横向半值线宽和轴向半值线宽公式.本研究为波带片作为一种光学元件提供了一理论基础. 相似文献
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衍射光栅的傅里叶分析方法 总被引:3,自引:0,他引:3
本文用衍射理论中的傅里叶分析方法,分析光栅在各种不同情况下的夫琅和费衍射现象中,其衍射屏上的复振幅分布、光强分布及频谱分布的规律。对于衍射光栅的应用具有指导意义。 相似文献
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Based on the Fourier transform method, a simple closed-form expression for the on-axis power spectrum of ultrashort Gaussian pulsed beams in diffraction at a circular aperture is derived, which permits us to study spectral changes both analytically and numerically. It is shown that for diffracted pulsed beams there exist spectral red and blue shifts, spectral narrowing, and spectral switches in the near field. The aperture diffraction plays an important role in spectral switching, but both the truncation parameter and bandwidth (or equally, Fourier transform limited pulse duration) affect the behavior of spectral switches. 相似文献
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Lü Baida & PAN Liuzhan . Institute of Laser Physics Chemistry Sichuan University Chengdu China . Department of Physics Luoyang Normal College Luoyang China . State Key Laboratory of Laser Technology Huazhong University of Science Technology Wuhan China Correspondence should be addressed to L Baida 《中国科学G辑(英文版)》2004,47(1):24-35
Inrecentyearsanewbranchofmodernphysicalopticscalledsingularoptics[1]hasbeendeveloped.In2002theworkinsingularopticswasextendedfrommonochromaticlighttospatiallyfullycoherentandpolychromaticlightbyGburetal.[2—4].Itwasfoundthat,whenaconverging,spatiallyfullycoherentandpolychromaticsphericalwaveisdiffractedatanaperture,anomalousspectralchangestakeplaceclosetozerosoftheintensityinthefarfield;i.e.thespectrumisredshiftedatsomepoints,blueshiftedatothers,andsplitintotwolineselsewhere.Thepredictionsofsp… 相似文献
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运用Rayleigh-Sommerfeld衍射积分,详细推导了二元环形孔径全空间在轴光强分布公式.由于未作明显的近似,所得公式对衍射距离大于数倍入射波长的衍射空间都是有效的.计算并分析了这种孔径轴线上的光强分布情况.结果显示,它的最大调制深度是入射光强的16倍,比圆形孔径或环形孔径大4倍,近场的光学层析能力比远场的强.在很近场区,二元环形孔径的在轴光强分布对孔径结构比较敏感,这些特性使这种孔径在光子学和光纤光学的应用方面具有潜在的价值. 相似文献
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基于离散衍射光的全息光栅的带宽压缩 总被引:6,自引:2,他引:4
提出一种基于离散衍射光的全息光栅的带宽压缩算法。人眼的视觉分辨率是有限的 ,即空间频率变化在Δfpupil以内时 (两根光线的夹角小于 0 .3°) ,不会察觉光线的跳变。首先对衍射光的频谱进行采样 ,使全息光栅衍射的是空间频率不连续的离散光 ,即在光栅的编码中只包含离散光频谱 ,且满足人眼视觉要求。这样 ,光栅的条纹函数为周期性函数 ,因此 ,在条纹编码中我们只需记录一个周期的函数值 (样本数 ) ,光栅的条纹函数的样本数可得到有效的压缩。然后在解码中通过简单的复制可恢复光栅条纹函数的全部样本值。采用这种方法 ,大大压缩了数据量 ,提高了传输速率 ,达到了动态显示的要求 相似文献
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The near-field diffraction of a nanometer aperture is studied in this paper according to the angular spectrum theory. The mathematic expressions of the near-field diffraction are presented, and the influences of the polarization of the electromagnetic field and the evanescent wave on the diffraction in near field are analyzed by means of vector and scalar diffraction theory, respectively. The transverse and longitudinal diffraction intensity distributions of a small aperture are numerically calculated, and the results show the near-field diffraction of a small aperture is influenced strongly by the vector property of the electromagnetic field and the evanescent component. 相似文献
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The rigorous electromagnetic theory of the diffraction of vector beams by an aperture is proposed and numerically evaluated by the diffraction of vector Gaussian beams by a circular aperture. The results are compared with those, by using the vector Rayleigh–Sommerfeld diffraction integrals and angular-spectrum expression theory, showing a good consistency. The numerical calculation shows that the result calculated by the rigorous theory is much more precise than those calculated by the integral method in diffraction near field, and a highly consistency reaches by the three methods in diffraction far field. A further extension of the theory is discussed. 相似文献
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Renault M Hadjar Y Blaize S Bruyant A Arnaud L Lerondel G Royer P 《Optics letters》2010,35(19):3303-3305
We report on a concept of compact optical Fourier-transform spectrometer based on bidimensional (2D) spatial sampling of a confined interferogram. The spectrometer consists of a nanostructured glass surface on which two light beams interfere in total internal reflection. Subwavelength spatial sampling of the interferogram near field is achieved by introducing a tilt angle between a 2D array of optical nanoantennas and the interferogram pattern. The intensity distribution of the scattered light is recorded on a 2D CCD camera, and a one-dimensional Fourier transform of the interferogram is used to recover the input light spectrum. Experimental results show a wide spectral bandwidth in the visible range, down to 380 nm, with spectral resolution of 1.6 nm around 780 nm. 相似文献
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二维圆周光综合孔径阵的优化排列及其成像特性研究 总被引:8,自引:4,他引:4
光综合孔径成像的原理是应用干涉原理在空间频率域中进行采样,并通过傅里叶反变换或其他数值变换方法得到空间分辨力远高于单个孔径成像系统的目标图像。由若干个相同的小孔径在二维圆周上优化排列组成的综合孔径成像系统可以在二维空间频率域中实现较为均匀分布的、具有无冗余度的采样点覆盖,为高质量实时成像提供了一个有效的途径。运用模拟退火算法对由7~16个子孔径组成的二维圆周综合孔径阵列进行优化排列。并依据光学衍射成像原理,从空域和频域两个方面详细分析了二维圆周上优化排列与均匀排列光综合孔径阵的成像特性。对7~16个子孔径组成的光综合孔径的仿真结果表明:无论是在空域还是频域上,子孔径直径增大、孔径数目增多以及综合孔径阵的优化排列都是有利于提高成像质量的。但综合后的子孔径的直径的增大,虽然能获得极高的角分辨力,却并不利于成像质量的提高。 相似文献
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Performance of laser-ultrasonic F-SAFT imaging 总被引:1,自引:0,他引:1
The resolution and signal-to-noise ratio of laser-ultrasonics to detect small and buried defects can be greatly enhanced by using the synthetic aperture focusing technique (SAFT). Originally developed in the time domain, SAFT can also be implemented in the frequency domain (F-SAFT) using the angular spectrum approach for a significant reduction in processing time. In this paper, an F-SAFT based data processing method especially adapted to laser-ultrasonic data is presented. This method allows for further significant improvements towards laser-ultrasonic imaging of small defects. It includes temporal deconvolution of the waveform data, control for an optimal aperture and frequency bandwidth as well as spatial interpolation of the subsurface images. All the above operations are well adapted to the frequency domain calculations and embedded in the F-SAFT data processing. Also, the aperture control and spatial interpolation allow a reduction of sampling requirements to further decrease both inspection and processing times. The above improvements are illustrated using laser-ultrasonic data taken from an aluminum sample with flat-bottom holes. 相似文献
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A simple method to measure the complex degree of spatial coherence of a partially coherent quasi-monochromatic light field is presented. The Fourier spectrum of the far-field interferogram generated by a mask with multiple apertures (small circular holes) is analyzed in terms of classes of aperture pairs. A class of aperture pairs is defined as the set of aperture pairs with the same separation vector. The height of the peaks in the magnitude spectrum determines the modulus of the complex degree of spatial coherence and the corresponding value in the phase spectrum determines the phase of the complex degree of spatial coherence. The method is illustrated with experimental results. 相似文献