【摘要】：空心光束是中心強度為零的一類環(huán)狀激光束,螺旋波陣面、中心相位奇異和空間傳播不變性等特性。這些特性使得空心光束在原子分子光學(xué),微納粒子操控,材料加工,量子信息等領(lǐng)域有廣泛的應(yīng)用�？招墓馐梢院唵畏譃闃肆靠招墓馐c矢量空心光束兩大類,多年來發(fā)展了多種理論上或者實驗上產(chǎn)生空心光束的技術(shù)。本文我們分別提出兩個產(chǎn)生空心光束的新方案：一個方案是利用非線性晶體材料ZnSe的非線性效應(yīng)產(chǎn)生標量空心光束。研究了基于非線性介質(zhì)材料的空心光束的產(chǎn)生原理,光學(xué)系統(tǒng)參數(shù)對產(chǎn)生的空心光束質(zhì)量的影響,并根據(jù)惠更斯-菲涅爾衍射積分計算產(chǎn)生了空心光束的強度分布以及其在自由空間的傳輸特性,同時研究了空心光束的暗斑尺寸(DSS)和最佳傳輸距離隨著入射高斯光束的束腰半徑的變化情況。研究表明,隨著傳播距離的增大,空心光束的強度分布呈現(xiàn)出一種對稱分布,隨著入射高斯光束束腰半徑的增大,最佳傳播距離Zopt和DSS都變大。通過這種方法產(chǎn)生的空心光束可以用作原子、分子光阱。如果將入射光改為橢圓高斯光束或者平頂高斯光束,那么經(jīng)過非線性晶體可以得到橢圓空心光束和平底空心光束,研究發(fā)現(xiàn)產(chǎn)生的橢圓空心光束在自由空間很長一段距離可以維持很好的空心特性。另一個方案是利用空心金屬波導(dǎo)產(chǎn)生矢量空心光束。將高斯光束通過2π相位板和透鏡相位調(diào)制產(chǎn)生的標量空心光束,入射到空心金屬波導(dǎo)的空心區(qū)域激發(fā)出TEo1模式的矢量空心光束,并在自由空間傳輸。根據(jù)矢量瑞利-索末菲衍射積分我們計算了通過空心金屬波導(dǎo)之后模式光強的矢量分布。結(jié)果發(fā)現(xiàn)經(jīng)過空心金屬波導(dǎo)產(chǎn)生的矢量光束在自由空間的場強分布是環(huán)狀的空心光束,而且在空間傳輸時一直都是空心分布,另外隨著傳輸距離的增大還會有類自聚焦現(xiàn)象出現(xiàn)。同時,我們還研究了由不同半徑的空心金屬波導(dǎo)得到的矢量空心光束在自由空間傳輸時類自聚焦位置和發(fā)散角情況,計算得到空心金屬波導(dǎo)空心半徑越大,類自聚焦位置越遠,而得到的矢量空心光束在類自聚焦之后發(fā)散角越小。另外金屬波導(dǎo)激發(fā)得到的TEol模,在自由空間傳輸時保持角向偏振不變。方案產(chǎn)生的角向偏振矢量空心光束可以用于原子分子透鏡。
[Abstract]:Hollow beam is a kind of ring laser beam with zero central intensity, helical wave front, center phase singularity and spatial propagation invariance. These properties make hollow beams widely used in the fields of atomic and molecular optics, micro and nano particle manipulation, material processing, quantum information and so on. Hollow beams can be divided into two categories: scalar hollow beams and vector hollow beams. In this paper, we propose two new schemes for the generation of hollow beams. One scheme is to generate scalar hollow beams by using the nonlinear effect of nonlinear crystal material ZnSe. The principle of hollow beam generation based on nonlinear dielectric material and the influence of optical system parameters on the quality of hollow beam are studied. Based on the Huygens-Fresnel diffraction integral, the intensity distribution of the hollow beam and its propagation characteristics in free space are calculated. At the same time, the variation of the dark spot size (DSS) and the optimum propagation distance of hollow beam with the beam waist radius of the incident Gao Si beam is studied. The results show that the intensity distribution of hollow beam exhibits a symmetrical distribution with the increase of propagation distance. With the increase of waist radius of incident Gao Si beam, the optimum propagation distance Zopt and DSS increase. The hollow beam produced by this method can be used as an atomic and molecular optical trap. If the incident light is changed to an elliptical Gao Si beam or a flat-topped Gao Si beam, then the elliptical hollow beam and the flat bottom hollow beam can be obtained through a nonlinear crystal. It is found that the elliptical hollow beam can maintain a good hollow characteristic at a long distance in free space. Another scheme is to generate vector hollow beams using hollow metal waveguides. The vector hollow beam of TEo1 mode is excited by introducing the scalar hollow beam of Gao Si beam through the 2 蟺 phase plate and lens phase modulation into the hollow region of the hollow metal waveguide and propagating in free space. According to the vector Rayleigh-Sommerfeld diffraction integral, we calculate the vector distribution of the mode light intensity after passing through the hollow metal waveguide. The results show that the field intensity distribution of the vector beam generated by the hollow metal waveguide in the free space is annular hollow beam, and it has always been hollow distribution in the space propagation. In addition, with the increase of transmission distance, there will be a similar self-focusing phenomenon. At the same time, we also study the quasi-self-focusing position and divergence angle of the vector hollow beam obtained from hollow metal waveguide with different radii in free space. The larger the hollow radius of hollow metal waveguide is, the farther the quasi-self-focusing position is. The smaller the divergence angle of the vector hollow beam is after the similar self-focusing. In addition, the TEol mode excited by metal waveguide keeps angular polarization invariant in free space transmission. The angular polarization vector hollow beam can be used in atomic and molecular lens.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN241

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相關(guān)期刊論文 前1條

1 呂百達,羅時榮,張彬;平頂高斯光束的相關(guān)概念和對稱化變換[J];強激光與粒子束;1999年04期

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本文編號：2275594